Basic Fuse Question Philips TV

[edy]

Hi folks,

I have a basic question. My Philips TV died and so I took a crack at it (as Dave Jones would say.... "Don't Turn It On... Take It Apaaaarrrt!"). I suspected a capacitor as I have replaced caps on my Samsung before. Anyways, I opened it up and first thing I noticed was a blown FUSE!  See the attached photos.

So I just want to clarify the type of fuse to replace it with. It is marked 125V 4A, but whether it is fast, slow, time-delay, etc... I'm not exactly sure. The part number on it is <PS>E NSF FBT. From a Google Search I gathered it is made by NSF and it is "Fast Blow Type"? I found this website but it only lists 250V fuses and I have a 125V 4A one:

http://nscable.co.jp/products/fuse/glass/04-3/index.html

If anyone can explain why Fast Blow versus Slow Blow and Time-Delay or Semi-Time Lag and what exactly the applications are typically for these types it will help me understand. My assumption is that fast blow is preferred to avoid damaging the appliance, but that short non-critical current spikes (say at power-up time) may mean more fuse replacements over time.

[Tandy]

Typically a fuse is marked with a T or an F T4A or F4A. F being Fast and T being time delay.

Time delay (slow-blow) fuses are used on equipment where there is an inrush current, in other words it needs moor power to start-up. This is typically inductive loads like motors or resistive loads that change rapidly with temperature like light bulbs.

In your TV it is more than likely a standard fast blow fuse.

BEFORE YOU REPLACE THE FUSE
Fuses rarely blow for no reason, you should first investigate any obvious sources of short circuit.

[Tandy]

PS chances are that the MOSFET on the switch mode PSU has failed and causing a short on the power supply.

[retiredcaps]

I suggest checking the 4 diodes acting as the bridge rectifier to see if they are shorted as well.

[Vito_R]

Yes most likely a fast blow fuse.  Before replacing the fuse make sure you check ALL diodes and transistors for shorts or leaks as you most likely have a bad component that blew the fuse. While you're at it being it is a TV SMPS I would also highly recommend you check all Electrolytic caps and even replace them if they are cheap Chinese capacitors often used in these power supplies and often the cause for repeated failures in these TVs.  Don't just change the bad ones, replace them all with high quality low ESR Japanese Nichicon caps like PW, HE, or HW series. You will just save yourself time opening up the tv again in the future.

[SeanB]

Fast blow fuse, you can use the 250V one to replace it with no problem. Check the diodes and transistor are not shorted ( easy as they are on the top) and check across the mains input for shorts and try it again. As it did not blow too violently it likely went out from a mains spike that operated the transient suppressor on the board.

[wraper]

Time delay (slow-blow) fuses are used on equipment where there is an inrush current, in other words it needs moor power to start-up. This is typically inductive loads like motors or resistive loads that change rapidly with temperature like light bulbs.

In your TV it is more than likely a standard fast blow fuse.

No! SMPS is the device where very high inrush current is present while primary capacitor is charging. Therefore usually slow blow fuses are used in SMPS. Anyway there is T4A of F4A written on the fuse which will solve the dilemma.

[Vito_R]

Time delay (slow-blow) fuses are used on equipment where there is an inrush current, in other words it needs moor power to start-up. This is typically inductive loads like motors or resistive loads that change rapidly with temperature like light bulbs.

In your TV it is more than likely a standard fast blow fuse.

No! SMPS is the device where very high inrush current is present while primary capacitor is charging. Therefore usually slow blow fuses are used in SMPS. Anyway there is T4A of F4A written on the fuse which will solve the dilemma.

No they are Fast acting fuses not slow blow.

[wraper]

Time delay (slow-blow) fuses are used on equipment where there is an inrush current, in other words it needs moor power to start-up. This is typically inductive loads like motors or resistive loads that change rapidly with temperature like light bulbs.

In your TV it is more than likely a standard fast blow fuse.

No! SMPS is the device where very high inrush current is present while primary capacitor is charging. Therefore usually slow blow fuses are used in SMPS. Anyway there is T4A of F4A written on the fuse which will solve the dilemma.

No they are Fast acting fuses not slow blow.

How often do you repair SMPS to say that? In my experience they can be either type.

[Vito_R]

Almost everyday and these TV SMPS always use Fast acting fuses. Slow blow would not provide adequate fire protection and safety in a TV.  From my understanding the fast acting fuses are still designed to provide a certain tolerance against surge currents and shouldn't blow instantly unless there is a short circuit or reach a certain threshold current and time based on the fuse's datasheet.

[edy]

Thanks for all the help. I took out the power board and took some photos. I can't find any obvious problems. I understand I am looking for shorts but I am having issues testing components in board using my multimeter set for continuity. For example, the diode bridge has no continuity, so using resistance I am getting the same values whether I test forward or reverse on each diode, probably because they are in circuit and I am able to get flow through the other. If I had them out of circuit I should get infinite resistance going backwards through the diode, no? As far as caps go, I don't see any damage. If it is that large blue one, how would I go about checking it? Just test resistance across it? I tried another diode in circuit and it tested as continuous in one direction... but then tapping it a few times it stopped beeping... then I tried it in reverse and it beeped a few times, then it stopped... and then forward direction it beeped again and so on. It was like I was charging up something in circuit with it and that was causing the strange behaviour. I guess I will need to de-soldering each component to test?

[edy]

More close-up photos...front and back of the hot side of power supply.

[edy]

Here are some components on the cold side of the board. Probably not an issue, just for those curious to see.

I found this on another thread: http://www.badcaps.net/forum/showthread.php?p=426429

I was doing repair on an Emerson LED TV LE220EM3 and there was a HAI 7209PC chip on board for the LED lighting circuit. I was hoping that this HAI 7209PC was an replacement for HAI 7207PC but it not. The HAI 7207PC is defective straight out the factory.Pin 6 and 7 will short out in time and then your fuse will blow. Your Idea is good (the heat sink or fan) for HAI 7207PC chips that are still functional (MAYBE).The inverter is the only solution for now

[Vito_R]

Thanks for all the help. I took out the power board and took some photos. I can't find any obvious problems. I understand I am looking for shorts but I am having issues testing components in board using my multimeter set for continuity. For example, the diode bridge has no continuity, so using resistance I am getting the same values whether I test forward or reverse on each diode, probably because they are in circuit and I am able to get flow through the other. If I had them out of circuit I should get infinite resistance going backwards through the diode, no? As far as caps go, I don't see any damage. If it is that large blue one, how would I go about checking it? Just test resistance across it? I tried another diode in circuit and it tested as continuous in one direction... but then tapping it a few times it stopped beeping... then I tried it in reverse and it beeped a few times, then it stopped... and then forward direction it beeped again and so on. It was like I was charging up something in circuit with it and that was causing the strange behaviour. I guess I will need to de-soldering each component to test?

Hi Edy,

You need to use the Diode test function on you multimeter to test for forward voltage drop in all diodes and transistors.  Voltage should indicate roughly 0.4-0.7v If you get a voltage indication on one side then reverse your leads and it should show no reading the other direction.  If you get a reading then unsolder one leg of the diode and test again to confirm the diode is not leaky.  If you have a reading in both directions (leaky) or 0V then it indicates a short and your component is defective.  O/L in both directions is an open.  Careful testing the transistors as some could be Mosfet and there is a slightly different method to test them as you have to turn them on.  Just check the part number of that transistor on the heat sink to see if it's a mosfet and then test it. They can sometimes fail.  You would also need to desolder the mosfet to test it. 

[Vito_R]

To test the caps you should use an ESR meter to check for high ESR which would indicate they are bad.  If you don't have one then unless these caps are high quality Nichicon, Rubycon, United Chem, etc.. I would simply replace all Electrolytic caps with low ESR Nichicon PW, HE, or HW series.  You will probably extend the life of the power supply for many years after as most manufacturers used cheap chinese caps in them for some reason. Before you do that confirm your issue with the fuse blowing is resolved and you have no more shorts.  Then if you want to upgrade the caps go ahead.  Make sure you use only LOW ESR caps to replace them.  You can find them at Digi-key or Mouser.

[Vito_R]

Just checked for you and the K5A50D is a Mosfet.  Desolder it and test it by using the diode function but you need to turn on the gate.  Test it using this method:

Connect the 'Source' of the MosFet to the meter's negative (-) lead.

 1) Hold the MosFet by the case or the tab but don't touch the metal parts of the test probes with any of the other MosFet's terminals until needed.

 2) First, touch the meter positive lead onto the MosFet's 'Gate'.

 3) Now move the positive probe to the 'Drain'. You should get a 'low' reading. The MosFet's internal capacitance on the gate has now been charged up by the meter and the device is 'turned-on'.

 4) With the meter positive still connected to the drain, touch a finger between source and gate (and drain if you like, it does not matter at this stage). The gate will be discharged through your finger and the meter reading should go high, indicating a non-conductive device.


Check that it is working and does not indicate a dead short.

[Zero999]

Time delay (slow-blow) fuses are used on equipment where there is an inrush current, in other words it needs moor power to start-up. This is typically inductive loads like motors or resistive loads that change rapidly with temperature like light bulbs.

In your TV it is more than likely a standard fast blow fuse.

No! SMPS is the device where very high inrush current is present while primary capacitor is charging. Therefore usually slow blow fuses are used in SMPS. Anyway there is T4A of F4A written on the fuse which will solve the dilemma.

No they are Fast acting fuses not slow blow.

How often do you repair SMPS to say that? In my experience they can be either type.

It depends on where the fuse is. If it's before the main filter capacitor, it's more likely to be slow blow. If it's after the main filter capacitor, it's more likely to be fast blow.

If the filter capacitor is fairly large, there will some sort of inrush limiting.

[edy]

Hi everyone,

Thanks for the help. I bought some fuses and the guy at the electronics shop said try to replace the fuse one time and see what happens, but only once. So that's what I did.... I placed a 4A/125V fast-blow fuse and blow it did!      The minute I plugged in the TV I saw the lights flicker and I think that was basically when the magic smoke was released from the fuse. Obviously these TV's are "always on" the minute you plug in they have a standby power draw to power the soft-touch buttons on the front and also the circuit listening for the remote control.

Ok, so now it is on to a real detective and repair job. First thing is I removed the power supply board from the back of the TV so I can easily work on it. I'd like to somewhat figure out the schematics here so I can understand what is going on. From what I can gather from the board (you can look at the pictures and let me know if this is correct)....

1. Mains enters in LIVE/NEUTRAL and the LIVE immediately passes through the fuse in series

2.  There is a resistor across the other side of the fuse and neutral...  Brown/Red/Green/Gold = 1.2Mohms
  - I tested it, measures 1.08Mohm. I figured if the resistor shorted it would blow the fuse. But it is ok. I don't think resistors fail that way anyways... they would if anything break completely and go to infinite resistance.

3. Next also in parallel with the resistor (crossing from other end of fuse to neutral) is a blue cap-like flat component with part number SVR 10D 471K SEC C. There is a "Z" written on the board under it. I assume this is a Varistor. Reading up on it looks like it is a surge protector, clamping the voltage down if there is a splike.

4. Next, also in parallel with the resistor and the varistor is that large blue box-like component with 470nK275V X2 PCX2 337 MK written on it. Google reveals it is a Pilkor component... Interference suppression film cap. Reading up on it, sounds like it EMI/RFI suppression to reduce noise/interference and spikes as well.

Anyways, none of these devices are shorted.... so if the resistor, varistor or cap were shorted that would immediately short the LIVE and NEUTRAL through the fuse.

So continuing on.... I looked up the next part and guess what.... A service manual turned up!   

HERE IT IS:

http://diagramasde.com/diagramas/otros2/PL12.0%20EN%20040812.pdf

The manual says to check each component on the primary side for a short circuit, and each rectifying circuit on the secondary for a short. So I took out the multimeter and placed it across all the diodes (in both directions) using continuity tester and I had a couple of the diodes test continuous. But looking closely at the circuit, I noticed one of the diodes that was continuous was in parallel with a resistor valued at only about 0.68 ohm.... so I can't test that diode unless I remove it from the circuit. The other one is a bit more complex.

I've attached the power supply block diagram from the manual I linked above....

Any guidance would be appreciated. I think the next step is to begin desoldering diodes and replacing caps? I don't know which direction to go first here.

[edy]

I've attached page 43 from that service manual I linked previously.

[Vito_R]

Check all those diodes for shorts or leaks.  Desolder one leg of each if needed. Check all transistors and what's often the culprit is the Mosfet.  Carefully check that.  Do you know how to test a Mosfet?  Please just re-read my previous posts earlier. 

[edy]

Thanks Vito_R for the Mosfet explanation. I am not exactly clear on how to do this. I found the explanation you gave here as well:

http://www.utm.edu/staff/leeb/mostest.htm

Should I be desoldering the Mosfet or can I test it in-circuit? Here is what I found.... The mosfet has G/D/S for leads 1/2/3 going from left to right looking at the picture when the Mosfet is facing us with the screw head showing that connects it to the heat sink.

a) set multimeter to diode/continuity setting but have it on diode function
b) I put negative probe (black) on source and positive probe (red) o gate... Shows 0.100 V.
c) then I put positive (Red) lead on drain while still holding negative on source.... multimeter shows 0 V.
d) while still in same position as in (c) above... I touch the gate with my finger while trying to holding the probes the same way as before (red on drain, black on source).... Guess what, NOTHING HAPPENS.

Also when I put positive (Red) on GATE, I get the same 0.100 V whether the negative (black) probe is held on drain or source.

Regarding resistance/continuity.... I get 121 ohm between GATE-DRAIN and also GATE-SOURCE.... And I get 0 ohm (continuous) between DRAIN and SOURCE. So... Does that mean there is a short through the Mosfet?

Now regarding the Diodes...My multimeter has the diode and continuity on the same position on the rotating knob. I usually press a function button to toggle between diode and continuity. When I measured some of the diodes I was getting 0.541 V on average for all the bridge rectifier diodes (whether I have the red/black probes in one direction and the other).

[Vito_R]

You must absolutely desolder the mosfet and take it completely out of circuit for that test to work. Only use the diode test function on your meter.  Do that and test it again.  Desolder one leg of each of the diodes and test again. 

[edy]

I removed the MOSFET ( I've attached a picture) and there is continuity between the drain and source (middle and right pins on picture).

I am getting 148 ohm reading between gate-drain (left and middle pin) and gate-source (left and right pins) consistently... but 0 ohm between middle and right... So I believe this is a FAIL.

Should I go about testing everything else too or can I take a chance and just put in a new MOSFET and fuse and see what happens?

Also, I am not sure if I must use the exact same part or if I can get away with a similar spec. For example, I go on Sayal.com and can't find the exact part but there are tons of Mosfets... how do I know? Or can I order a one off part from Mouser? I found it on there... STA4,Q,M and STA4,Q... difference? Package or case? Seems I can buy one part from Mouser but have to buy bulk from Digikey. If Sayal.com had a similar part that would be easier as I can just drive over to their store.

[Vito_R]

Can you repeat the test with the diode function and try to trigger the gate like in the procedure? Just want to be sure.  Yes you can get it from mouser, looks like its the same one on their site.  And yes I would still test the other components too just to be sure you don't have any multiple failures.  I always like to spend a little extra time troubleshooting and double check everything to avoid any unpleasant surprises, but that's just me, others may have their own opinion.  I also like to check for any open resistors around that circuit.  Although if they do not show any signs of burning usually they are ok but sometimes they can still open up internally especially if they are fusible or flameproof resistors.

[edy]

An interesting finding....

After I removed that MOSFET, I have re-tested the 4 diodes from the bridge rectifier on the board (without desoldering them) and I have entirely different results. Here is the initial results:

WHEN *FAULTY* MOSFET WAS ON BOARD:

All 4 diodes measured 0.541 V (using diode test on multimeter) in BOTH directions.

Now that I removed the MOSFET.....

The 4 diodes still measure 0.541 V but only the proper direction. That is, I have to put the red/black leads for the proper polarity of the diode to get a forward voltage reading. Otherwise in reverse I get O L (open) result.

Unfortunately, other diodes still show forward/reverse readings so I will have to desolder one end because there is probably another path through the circuit. But at least the bridge has been rendered "testable" by removing the MOSFET and not having to desolder every one of the diodes, so I should be safe to say the bridge rectifier diodes are ok.

[edy]

I have tested more diodes on the board. Looking at the schematic (see my last photo attached), the MOSFET at Q601 shorted drain to source... and if you follow the source down it grounds through 1ZB36BL Zener diode D608.

Well I happened to find this was the only diode shorted on the board. I completely removed it and I get zero resistance both ways!!!

So I think I need to replace the MOSFET and the Zener and I should be ok? I hope I didn't miss anything.

Now, the MOSFET is 500v 5A but I can get a 500v 4.5v from my local supplier. Is that going to be ok? Or should I go up? And is there any other important number I need to watch out for? And I can't seem to find that Zener diode anywhere on Sayal.com, and not sure the compatible part. So I don't know whether to just buy this stuff from Mouser or Digikey and pay and wait for shopping.

[Vito_R]

Glad you also caught that shorted diode.  If you didn't it would of blown your Mosfet again.  That's why it's so important to double check all components to avoid any surprises.  Also running a quick check of any resistors in that circuit to make sure none have opened up is also a good idea.  I highly recommend you replace the mosfet with an original part and get it from mouser, they seem to have it in stock.  Good luck

[edy]

Thanks, I never thought a simple blown fuse would lead to such an interesting detective game. This was a great exercise for me in learning. I've attached the parts list from page 69 and I can't find that Zener diode anywhere on Mouser or Digikey or Sayal. I want to order that TK5A50D from Mouser but I notice they have 2 options... which do I get? And what equivalent Zener? I can't find 1BZ36BB anywhere.


Looks like this has happened and reported here:

http://www.badcaps.net/forum/showthread.php?t=22454

The more I look the more I find!

[Vito_R]

Thanks, I never thought a simple blown fuse would lead to such an interesting detective game. This was a great exercise for me in learning. I've attached the parts list from page 69 and I can't find that Zener diode anywhere on Mouser or Digikey or Sayal. I want to order that TK5A50D from Mouser but I notice they have 2 options... which do I get? And what equivalent Zener? I can't find 1BZ36BB anywhere.

Thats what troubleshooting is all about, being an electronics detective.

I saw a seller from the UK selling the 1BZ36 on ebay.  Shipping is usually fast from UK to Canada, I recommend that.  See those > ! < marks next to those components means the manufacturer recommends replacement with original components only because they are safety critical.  Try to give the manufacturer a call sometimes you can get lucky and they still have them in stock.  If not you can try to find an equivalent that matches or exceeds the specs of the Zener.  Might want to have a look at this on digikey: http://www.digikey.com/product-detail/en/1N4753A-TAP/1N4753A-TAPCT-ND/3104322 but I still recommend you use the original.

The mosfets both look the same to me.  I would recommend you order at least 2 so you have spares.  Same with the Zener.

I would highly recommend you check R611 that 0.68ohm 2W resistor to see if it's open.  If it is you must replace it or your parts will burn out again.  Desolder one leg and test it.  I would also check R608.  If it would be me I would check all resistors in and around that circuit for any opens.   I also would check the other transistors just to be on the safe side.  At the same time if you have any of those crappy chinese electrolytic capacitors on the board (which you probably do) I would replace them all with Nichicons PW, HE, or HW series after you confirm your board is working again.   Good luck

[edy]

And the plot gets thicker! I read that thread on the previous post from badcaps forum and someone also suggested the transistor Q602 on the gate of the MOSFET may also blow... So I de soldered Q602 and also the same part located at Q656 on the board for comparison.

I used the test for transistor using a multimeter shown here:

http://www.vetco.net/blog/?p=184

The transistor at Q602 showed a voltage drop from emitter to collector in both directions while the good transistor at Q656 showed 0L for both directions (swapping pos/neg leads) as expected for a good NPN. So that is another defective part found....

Note that without unsoldering the good NPN also showed some strange results. The amount of work involved and time is almost economically reaching the limits for this cheap TV. But I don't want it to end up in landfill and I am using this as a learning opportunity.

[Vito_R]

Well that's why I kept saying test all parts connected to that circuit and the remaining transistors.  Better to be safe then sorry and have all those parts burn out again cause we missed a component.  This was definitely a multiple failure and when that happens I just test all semiconductors and resistors for failures just to be sure it doesn't take out my new components if I happen to miss something.  A good electric vacuum pump desoldering tool is our best friend in a situation like this.

[edy]

Hi Vito_r,

Thanks! Yes indeed I took R611 out and it has no continuity... 0L resistance! When will it end! If I have to keep removing components to test this is going to drag on forever... I may as well just find another power supply board and just replace the whole thing. 

[Vito_R]

Hi Vito_r,

Thanks! Yes indeed I took R611 out and it has no continuity... 0L resistance! When will it end! If I have to keep removing components to test this is going to drag on forever... I may as well just find another power supply board and just replace the whole thing. 

You're getting close to the end don't give up.  Just be patient and meticulous and you should be successful with this repair.  Sometimes I find taking a break for a while and coming back to it later is less stressful.  Take the time and do it right so it's not all for nothing.  Keep up the good work.

[Vito_R]

Just want to add that the fellow at the electronics store you went to that sold you the fuse gave you bad advice.  He should never have told you just install the new fuse and see what happens.  This is possibly what caused more failures on your board.  Even the manufacturer mentioned it in the block diagram, make sure you check for all other faulty components before replacing the fuse.  Anyways can't cry over spilled milk.  Just check everything and replace whatever is bad like you're doing.

Update:  I recommend you also check D604 and all surface mount diodes.  Also recommend you re-check the transistors for proper forward voltage and no leakage.  Make sure you don't miss any of them cause there could be more.  IC601 may also be an issue.  Suggest you replace it to be on the safe side while you're ordering parts.  This one is a special situation where you really need to be meticulous and not overlook anything.  If you do that I'm sure you will be successful here.

[Tandy]

The amount of work involved and time is almost economically reaching the limits for this cheap TV. But I don't want it to end up in landfill and I am using this as a learning opportunity.

It is taking a lot of time partly because it is something new to you but if you regularly repair things like this you get a feel for the most common type of fault and it doesn't take so long. Sometimes as components are so cheap I tend to order a handful of components to replace anyway as it takes less time to replace half a dozen components in one go than to remove each one, test it and then order them.

Well done for persevering with it, like you say it is a learning experience and although it is only a chap TV this time what you have learnt troubleshooting the problem may help with more valuable things in the future.

[tom66]

These are crappy FUNAI LCD/LED-LCD TVs. They are not built by Philips, just a re-badge job.

Likely you'll find a shorted diode on the secondary which will take out the badly designed primary side. It is a ringing-choke converter -  a self oscillating flyback (yes in a modern consumer product that's pretty rare.) They are horrible to repair.

[edy]

Yes I saw that.... I keep seeing threads on other boards as well (like badcaps forum) showing various models. In fact, I found an Amazon listing here for a repair kit and I could probably get another power supply board Part# BA21N0F0102... for $20-30 (maybe cheaper on eBay):

http://www.amazon.com/Magnavox-BA21N0F0102-Component-Repair-Kit/dp/B00KTD918K

They are labelled Magnavox, Emerson, Sylvania... all crappy brands. It is unfortunate Philips decided to do this as well and throw their brand name into the crap pile with the rest by doing this.

At this point I am not sure whether it is cheaper just to buy all the parts from Mouser/Digikey and go through the trouble of desoldering and testing, although it is a good exercise if anything in learning how to trouble-shoot and test parts.

I also see on eBay a bunch of "repair kits" which list 7 or 8 items, I presume the most commonly blown parts they have found from experience? That will at least help me track down more faults... Notice none have CAPS.... Only the MOSFET, some associated resistors and diodes and transistors.

[Vito_R]

Going with a repair kit could save you some time in terms of ordering everything individually and possibly from different suppliers.  Just make sure the parts they use are genuine and not some knock off chinese counterfeits you often see on ebay.  That's why whenever possible my personal preference is ordering directly from the big distributors to lessen the chances of any headaches.  Also make sure you check your surface mount components too, diodes or any transistors, D604 could be another potential fault. I would also pay particular attention to R602, R608, Q600, D607, D610, and D640.  Check them for faults and also see if any of those repair kits include those too.  If you really want to keep those crappy electrolytics on the board I would at least at a minimum test all of them with a good esr meter.  After you confirm your board is working again, I don't think it's worth it leaving them there after all the work you've done to repair it.  Why leave crappy caps in there that most likely will eventually fail?  Just my own personal opinion.  Agreed this is well worth the learning opportunity for you and the tough jobs is where you gain the most experience.  Good luck and keep us posted.

[Vito_R]

Just realized this post should really be under the repair category and not under beginners as it has turned into an excellent repair example.  Wonder if it is even possible to move it at this point.  Maybe we can ask Dave ?

[cybertronicify]

Time delay (slow-blow) fuses are used on equipment where there is an inrush current, in other words it needs moor power to start-up. This is typically inductive loads like motors or resistive loads that change rapidly with temperature like light bulbs.

In your TV it is more than likely a standard fast blow fuse.

No! SMPS is the device where very high inrush current is present while primary capacitor is charging. Therefore usually slow blow fuses are used in SMPS. Anyway there is T4A of F4A written on the fuse which will solve the dilemma.

On some SMPS's if the inrush current to the capacitors are too high, they will add a resistor inline so eliminate that. That is why some SMPS's do not spark when plugged in the mains instead that slowly charge the capacitor. Slowly as in a span of 1 second.

[edy]

I thought this was going to be any easy fix too! And I'm a beginner... Little did I know it would be involving so many components. I guess there is a "domino effect" where a component fails and starts taking out more and more parts until finally you have an entire chain or network of components fried.

I'd like to know the time sequence of how things failed until finally the fuse blew. I guess the chain of events can be worked out, looking at "what if". For example, if the MOSFET is first to go... what does it do to the other components around it, and what is the chain reaction until finally the fuse goes? What if that Zener shorted first, or what if the Resistor opened up or transistor shorted... each would have a different effect on the circuit path and voltages and currents as the failed component would effective "change the circuit" and all of the charges flowing through it.

Understanding those can help build a "pattern map" of what parts would typically be involved with each type of failure, depending on which components are affected you can work out what may have failed first and how the entire chain of events occurred.

[Vito_R]

I thought this was going to be any easy fix too! And I'm a beginner... Little did I know it would be involving so many components. I guess there is a "domino effect" where a component fails and starts taking out more and more parts until finally you have an entire chain or network of components fried.

I'd like to know the time sequence of how things failed until finally the fuse blew. I guess the chain of events can be worked out, looking at "what if". For example, if the MOSFET is first to go... what does it do to the other components around it, and what is the chain reaction until finally the fuse goes? What if that Zener shorted first, or what if the Resistor opened up or transistor shorted... each would have a different effect on the circuit path and voltages and currents as the failed component would effective "change the circuit" and all of the charges flowing through it.

Understanding those can help build a "pattern map" of what parts would typically be involved with each type of failure, depending on which components are affected you can work out what may have failed first and how the entire chain of events occurred.

As Tom66 mentioned, this is a crappy power supply with a poor design which was unfortunately used in many different TVs.  However I would highly suspect that replacing the fuse before confirming that there are no faulty components most likely caused the high number of failures to occur.  Those guys working in the electronics stores are not technicians or engineers and usually have little to no background in electronics.  It is hard to say what started it, if I had to guess I would suspect the Zener and/or the source resistor R611 started the problem.

[edy]

I found a bunch of repair power supply component kits. The kits at least point me in the right direction as they list a handful of parts.... So I will check all the parts you mentioned. Hopefully I'm close to discovering them all! Here are some kits or replacements:

http://www.shopjimmy.com/emerson-a2176mpw-001-power-supply-led-board-component-repair-kit.htm

http://www.usefulparts.com/tv-parts/lcd-tv/power-supplies/power-supply-a2176022-from-philips-22pfl4507-f7-a2176ut

I will have to keep hunting for details and then get some help on the Mouser or Digikey order, as I have never dealt with them.

[Vito_R]

Take your time and i'm sure you'll find all of them.  The greatest benefit here is the learning experience you're getting.  Good luck and keep us posted.

[tom66]

They are labelled Magnavox, Emerson, Sylvania... all crappy brands. It is unfortunate Philips decided to do this as well and throw their brand name into the crap pile with the rest by doing this.

Philips got out of the TV business about 2 years ago... along with Toshiba, Sharp, JVC, Hitachi and Sanyo. With the exception of very high-end or large TVs, Toshiba and Sharp are only re-badging crap models now.

[ijchan223]

i wouldn't bother with buying the kit, because you don't learn anything form just swapping components out and you can get the while board on ebay for the same price.

[edy]

I have attached part of the schematic and highlighted in RED the components that are being provided as part of the Repair Kit (which I list below). I have already confirmed that the MOSFET Q501, Resistor R611 and Transistor Q602 are fried on my board. It seems my rectifier diodes D601 through D604 are ok. But I have not checked some of the other components provided in the Kit.... So perhaps the kit will guide me on which parts to check next.

From an electronics failure point of view, it seems these parts are suspect and if something blows it will take most or all of these things out before the voltages and currents settle to a point where they cannot damage the remaining parts. Keep in mind I have no easy way to test the C605 cap with my multimeter and it is best if I just replace it as a matter of fact, and some of the other components.

So do I buy the KIT or the BOARD?

The links below (ShopJimmy) seems to be the most reliable source I found.... If anyone knows another, please let me know. I don't think I will be able to order all those individual parts from Mouser/Digikey and get it under $15 as an individual user. And I have not found the board at less than $40 from any reputable sources on eBay. Also it seems the source below warranties the board for 180 days whereas the kit has no warranty at all (obviously). So I suspect the BOARD will be the best way to go for the replacement.

KIT for $15.57:

http://www.shopjimmy.com/emerson-a2176mpw-001-power-supply-led-board-component-repair-kit.htm

BOARD for $39.43:

http://www.shopjimmy.com/magnavox-a21n0mpw-001-power-supply-led-board.htm#

[Vito_R]

Seems like the repair kit is an affordable option to go with.  Shopjimmy is usually a reliable source for those kits from the feedback I've heard on other forums.  I personally prefer to source my own parts just to be sure of what I'm getting.  But at $15 you can't really go wrong.  You've already learned a lot doing the troubleshooting now it's down to getting those replacements in.  Just a caution reminder, be 100% sure you didn't miss finding any other faulty components on this board because it has a tendency to cascade fail quite easily.  A lot of technicians initially power these boards up after a repair with a variac (variable AC transformer) and slowly bring up the voltage and monitor the board for results.  Another trick techs use is the old light bulb in place of the fuse technique.  This current limits the load so you can initially see if your board is still in a short circuit condition or drawing too much current.  After that you need to remove the bulb and replace the fuse, test, and cross your figures she doesn't blow again.            Good luck 

[edy]

On a bit of a side-track, to test my caps.... since I don't have an ESR meter, I looked at the video posted by w2aew below. I have a function generator that could possibly do about 44kHz max at 1V square and an oscilloscope. Would I be able to get any useful reading doing a test with it? I understand I'm looking for a low resistance in the higher frequencies.

I can test my resistors and diodes with a multimeter, using ohm and diode/continuity settings... even the transistors I can check diode voltage drops and hFE values on my digital multimeter. But the caps I am having trouble with. I am wondering what the easiest way to tell I have a good capacitor.

Here's the video I am referring to and wondering if my 44kHz 1V square would be good enough for any usefulness or if there is some other way I can know my caps are ok:

[Vito_R]

On a bit of a side-track, to test my caps.... since I don't have an ESR meter, I looked at the video posted by w2aew below. I have a function generator that could possibly do about 44kHz max at 1V square and an oscilloscope. Would I be able to get any useful reading doing a test with it? I understand I'm looking for a low resistance in the higher frequencies.

I can test my resistors and diodes with a multimeter, using ohm and diode/continuity settings... even the transistors I can check diode voltage drops and hFE values on my digital multimeter. But the caps I am having trouble with. I am wondering what the easiest way to tell I have a good capacitor.

Here's the video I am referring to and wondering if my 44kHz 1V square would be good enough for any usefulness or if there is some other way I can know my caps are ok:

Using an esr meter is really the most effective way I would recommend.  If you are not sure then just swap them out when you're ordering parts.  The cost is very minimal and you can replace them with some high quality low ESR Japanese caps that are extremely reliable.  Nichicon PW, HE or HW I find are the best but any of the other known brands like Rubycon, United Chemicon, Panasonic, any of their low esr (made for switching power supplies) series are great and extremely reliable.

[edy]

Ok, I went ahead and ordered the power supply repair kit from ShopJimmy shown here:

http://www.shopjimmy.com/emerson-a2176mpw-001-power-supply-led-board-component-repair-kit.htm

The shipping to Canada using USPS added another $7-8, so the total cost for my PayPal account was just under $23. If I can get my TV fixed by swapping out all the parts for the ones in the kit, for this cost, I will be happy.

I'll make sure to test other parts on the board as well, but my hope is that the "kit" essentially covers the normal failure mode and "cascading" failure of parts that usually ensues. Hopefully that will be it. If my board blows again, then I'll be forced to re-troubleshoot the entire thing again and either buy another kit and risk it again, or go for a whole board priced around $42 with shipping bringing it to $50-60:

http://www.shopjimmy.com/philips-a2176mpw-001-power-supply-led-board.htm

If it starts costing me that, I would have spent about half the cost of a new TV by the time I repair this one. I can get a new 22" for about $120-150.

I'll let you know what happens! Wish me luck on this one! May the EEVBlog force be with me. 

[Vito_R]

I'll make sure to test other parts on the board as well, but my hope is that the "kit" essentially covers the normal failure mode and "cascading" failure of parts that usually ensues. Hopefully that will be it. If my board blows again, then I'll be forced to re-troubleshoot the entire thing again and either buy another kit and risk it again, or go for a whole board priced around $42 with shipping bringing it to $50-60:

I would highly recommend you test all the other parts meticulously as we discussed, before you power the board with just the replaced parts from the kit.  It would be less expensive and more efficient to do that then to just Hope that the board doesn't blow again.   I'm sure you can catch everything if you are very careful and the tests you perform are 100% conclusive.  Good luck

[Shock]

This is an easy fix, you have found a very common problem the next time it will take you only a few minutes to check. If time is money don't get into electronics, but if you are starting to get into electronics/repair, get yourself an Capacitance and ESR meter.

The fuse is a symptom of the fault, not the cause of it, it never really is just the fuse. It's extremely common for components to fail like this. Don't expect a replacement board to be a magic fix all, it can be really advantageous to get a new one or have a working set when taking comparative readings though. A secondhand board always carries a risk of arriving with it's own problem and even introducing further faults.

Most people who want to repair something are too lazy to start checking a few components one by one with their multimeter, so congratulations on that.

Normally when repairers power up a device they use a variac or a dim bulb tester (latter can be made fairly cheaply), these are designed to limit current and reduce the chance of a component failing on first power up after repair. Without these you have to be on your game or else your effort is wasted. The same goes for ordering one of each capacitor, fuse, mosfet, you would normally get a few of each just in case.

[edy]

If time is money don't get into electronics

Yes I have found that out. I am doing this out of principle... I refuse to dump this into landfill after only 2 years . It may be "economically beyond repair" for me (but easy for someone more experienced), but the value of what I have learned in the process has offset that cost in time, which I would have needed to spend anyway to learn. This way I get some practical experience.

For example, some very valuable lessons from this fix include that when the fuse blows, don't just stick in another one (like the guy at the electronics shop said sometimes the fuses get "weak" or "tired").    Also that you need to test many components because it can take out quite a number. I also learned that I need to desolder many of them to properly test otherwise other current paths on the board will give me erroneous measurements on in-circuit parts. I also learned a few more functions on my multimeter that I rarely used (diode test, hFE test). I figured out I need to get an ESR meter or at least try to set up a square-wave gen and my oscilloscope to check caps and figure out if I can tell the difference between good ones and bad ones. I also learned that it can be sometimes tough to source equivalent components and that it may not be easy to get them cheaply either locally or in single quantities.

It has also taught me that I cannot trust anything lasting like they used to, and that I'd better keep learning because it is likely to keep happening more and more to all of these basic mass consumer electronics I buy.

[Vito_R]

If time is money don't get into electronics

Yes I have found that out. I am doing this out of principle... I refuse to dump this into landfill after only 2 years . It may be "economically beyond repair" for me (but easy for someone more experienced), but the value of what I have learned in the process has offset that cost in time, which I would have needed to spend anyway to learn. This way I get some practical experience.

For example, some very valuable lessons from this fix include that when the fuse blows, don't just stick in another one (like the guy at the electronics shop said sometimes the fuses get "weak" or "tired").    Also that you need to test many components because it can take out quite a number. I also learned that I need to desolder many of them to properly test otherwise other current paths on the board will give me erroneous measurements on in-circuit parts. I also learned a few more functions on my multimeter that I rarely used (diode test, hFE test). I figured out I need to get an ESR meter or at least try to set up a square-wave gen and my oscilloscope to check caps and figure out if I can tell the difference between good ones and bad ones. I also learned that it can be sometimes tough to source equivalent components and that it may not be easy to get them cheaply either locally or in single quantities.

It has also taught me that I cannot trust anything lasting like they used to, and that I'd better keep learning because it is likely to keep happening more and more to all of these basic mass consumer electronics I buy.

Hey Edy,

I'm happy to read your post.  It really says it all.  "but the value of what I have learned in the process has offset that cost in time, which I would have needed to spend anyway to learn. This way I get some practical experience."  SO TRUE 
That is what was most important to realize here.  It's not just about fixing a TV. The guy in the electronics shop proved my point with his statement of "fuses getting tired or something" shows he has no background in electronics and doesn't know what the hell he's talking about.  He's a total incompetent idiot that probably caused a lot more damage to your board then you had started with before you took his advice.
All the other points you made are excellent in learning the process of troubleshooting and component testing.  In the future you can take this advice and apply it to a more important repair.  I really hope you succeed here.  Just re-read my earlier post and continue to be very meticulous. Keep us posted.

[edy]

Yes... I will keep testing the other components but needed another tool....

I decided to take a gamble and pick up this cheap Mega328-based meter of which there are already plenty threads on EEVBlog... the "$20 ESR meter". I know it is a piece of garbage but as I am not doing any precision testing and just want to verify some parts tolerances, I figure it should do the job that my multimeter and old used CRO can't handle:

http://www.ebay.com/itm/NEW-Versio-Transistor-Tester-Diode-Triode-Capacitance-LED-ESR-Meter-MOS-PNP-NPN-/301159202930?pt=LH_DefaultDomain_0&hash=item461e7cc072

[Vito_R]

Yes... I will keep testing the other components but needed another tool....

I decided to take a gamble and pick up this cheap Mega328-based meter of which there are already plenty threads on EEVBlog... the "$20 ESR meter". I know it is a piece of garbage but as I am not doing any precision testing and just want to verify some parts tolerances, I figure it should do the job that my multimeter and old used CRO can't handle:

http://www.ebay.com/itm/NEW-Versio-Transistor-Tester-Diode-Triode-Capacitance-LED-ESR-Meter-MOS-PNP-NPN-/301159202930?pt=LH_DefaultDomain_0&hash=item461e7cc072

Well I guess it's better then nothing but I'm not sure if the ESR function will properly test capacitors using the industry standard 100Khz test frequency, nor would I know if this meter is capable of in circuit testing.  If you want a suggestion for a reasonably priced but very high quality ESR meter I would suggest the Bob parker Blue ESR meter.

This is the kit version but the fully assembled version is also available for just a little more:

http://www.ebay.com/itm/Anatek-Blue-ESR-Meter-Full-Kit-for-Self-Assembly-BESR-kit-/181463391631?pt=LH_DefaultDomain_0&hash=item2a400f9d8f


I could also suggest to look around ebay for some old second hand units of the older version with the RED display.  Sometimes you can find a bargain on it.

[Shock]

Actually the $20 ($10?) ESR meters work fine, they are multi function meters and they make a nice upgrade project as well for just a few dollars.

There are portable LCR meters now based on the Cyrustek ES51920 chipset (DE-5000 starts at $75 with free shipping on ebay). Bob Parkers meter only does ESR, so shop around before making a decision.

The RED version of the bob parker needs a programmer doesn't it?

[Vito_R]

Actually the $20 ($10?) ESR meters work fine, they are multi function meters and they make a nice upgrade project as well for just a few dollars.

There are portable LCR meters now based on the Cyrustek ES51920 chipset (DE-5000 starts at $75 with free shipping on ebay). Bob Parkers meter only does ESR, so shop around before making a decision.

The RED version of the bob parker needs a programmer doesn't it?

The Bob Parker ESR is a very high quality reliable meter that can effectively measure caps in circuit.  At this cost it worth the difference for quality test equipment and not having to worry about second guessing your measurements or doubting if those caps are good or not.  I don't waste my time with cheap $20 chinese testers cause I know I won't always be able to rely on them.  What programmer are you referring to for the red one?? Then just buy a used meter already assembled on ebay.

[edy]

So now I am waiting for the parts and meter.... ShopJimmy confirmed shipment of the "repair kit" and that is coming from the USA via USPS and I'm in Canada... so hopefully will arrive in the next week or so. The $15 Chinese meter may take 1 month or more from Hong Kong (or somewhere else in China).

The repair kit cost $15.57 with shipping $7.65. Meanwhile the Chinese meter cost $15 with "free" shipping. It is coming all the way from Hong Kong but taking forever. So far I've been lucky, all my Chinese ebay purchases have arrived but they take 1 month+. I don't want to wait to fix the TV so I will swap out the components in the meantime using the repair kit and then do my best to test the remaining components with my multimeter. When the ESR meter arrives I'll be able to test the last few components that I wasn't otherwise able to test, then hold my breath and power it on.

For the light bulb test, how do you suggest I do this? Do I get a socket and solder it across the fuse holder (perhaps on the other side of the PCB)? Do I use a regular incandescent bulb like 40W or 60W? I'm trying to figure out the math here. I am trying to reduce the amperage through the device so I need to calculate how much P=VI. So 40W = 120V x 1/3 Amp? Or 60W = 120V x 1/2 amp? 120W = 120V x 1A? Basically the greater the wattage the more current the bulb passes? What am I going for here and is there an issue with the TV supply not properly "resonating" as it is a switched mode? What should I be looking for when I power it up? An in-rush current with the bulb lighting up and then stopping to light as the current draw starts to reduce?

[Shock]

There is lots of info on google. A dim bulb tester is used for power up testing and prevents current from shooting up and damaging the device you're testing. Instead it lights the bulb to let you know to switch off. Incandescent bulbs are used, 60W for a 100W panel and 100W for a 200W panel should be fine. This gives you an idea of the circuit: http://www.antiqueradio.org/dimbulb.htm

As you can see from the diagram you plug your TV, Radio, Amp whatever your testing into the dim bulb tester. A resettable circuit breaker is handy if you go through fuses. These are normally made from spare parts people have laying about, I'll let you decide if this is beyond your skill level.

[Vito_R]

So now I am waiting for the parts and meter.... ShopJimmy confirmed shipment of the "repair kit" and that is coming from the USA via USPS and I'm in Canada... so hopefully will arrive in the next week or so. The $15 Chinese meter may take 1 month or more from Hong Kong (or somewhere else in China).

The repair kit cost $15.57 with shipping $7.65. Meanwhile the Chinese meter cost $15 with "free" shipping. It is coming all the way from Hong Kong but taking forever. So far I've been lucky, all my Chinese ebay purchases have arrived but they take 1 month+. I don't want to wait to fix the TV so I will swap out the components in the meantime using the repair kit and then do my best to test the remaining components with my multimeter. When the ESR meter arrives I'll be able to test the last few components that I wasn't otherwise able to test, then hold my breath and power it on.

For the light bulb test, how do you suggest I do this? Do I get a socket and solder it across the fuse holder (perhaps on the other side of the PCB)? Do I use a regular incandescent bulb like 40W or 60W? I'm trying to figure out the math here. I am trying to reduce the amperage through the device so I need to calculate how much P=VI. So 40W = 120V x 1/3 Amp? Or 60W = 120V x 1/2 amp? 120W = 120V x 1A? Basically the greater the wattage the more current the bulb passes? What am I going for here and is there an issue with the TV supply not properly "resonating" as it is a switched mode? What should I be looking for when I power it up? An in-rush current with the bulb lighting up and then stopping to light as the current draw starts to reduce?

As your light bulb question was already just answered by another member I won't need to repeat that.  You don't have to wait for your chinese esr meter to arrive to test your board.  It is unlikely the capacitors was the cause leading to the short circuit condition, but they should still be replaced or at least tested before you put your tv back together as even if they are still good they may eventually fail.  What's most important here is to ensure no semiconductors or resistors are still faulty.  If you have thoroughly checked your board, and replaced the defective components you found, you can then proceed with the light bulb test without testing the capacitors to see if the power supply is operational.  Good luck

[edy]

Thank you. I will proceed with building a dim bulb tester as explained... Thanks for the link! I am going to wire up the light socket in series across my live 3-prong plug wire to the plug socket outlet where I plug things for testing, and then return it back to the 3-pring plug (I have lots of computer cables). As far as ground is concerned, can I just connect ground from my 3-prong plug to ground of my testing socket outlet (obviously bypassing the bulb socket)? The TV only has 2 prong plug anyways. I will just need to make sure I keep polarity the same (so the wide slot is to wide slot on testing outlet). I will post a photo once I build it. I need to buy a few parts... hopefully they still sell regular light bulbs here and not those CFL crap.

[Shock]

If you make it with a properly connected earth wire, it's there when you need it. Sure show us your design.



 

[edy]

I purchased a few parts at my local hardware store for under $15. I have lots of computer power cables at home which I can cut and use (they are all grounded and have 3 wires... black, white, green). I've attached a diagram of how I want to wire up the dim-bulb tester. I had to use RED instead of BLACK otherwise it wouldn't show up well in the drawing... But RED = BLACK.

Following the pictures....

1. The red/white/green comes from my grounded 3-prong plug cord.... the wires are actually black/white/green.

2. I pass the red (black) into one side of the switch, then out to the bulb socket, then out to the "HOT" side (brass screws) side of my PLUG SOCKET.
- I do not think it matters whch way the switch is wired (top or bottom) or which way the bulb socket is wired

3. The other side of my PLUG SOCKET (silver screws) connects to the white wire that returns back to my 3-prong computer cord.

About the grounding....

I will screw the bulb socket, switch metal box and plug socket metal box all to a piece of wood.  I have a GREEN screw on the PLUG SOCKET which I should connect to the screw on the back of the metal box which houses it. I assume I should also connect the two boxes together as well with a green wire (the SWITCH socket box and PLUG box). The switch has no "ground screw" but the fact that it has a metal plate on the front and will be connected to the box will ground it. Finally, the green wire on the 3-prong computer power cable will connect to the switch box. The bulb socket has no grounding at all.

Therefore, the PLUG SOCKET will be grounded through both boxes.

[edy]

Ok, I've built the dim bulb tester. You can see the black wire from the power cable going through the switch and then to the bulb socket and finally to the hot side of the plug. I then have the white wire return back to power cable. The green connects to each box and also to the plug ground screw which is green.

What can I test with this rig that I know should work ok? I have 25, 40, 60 watt clear bulbs and can get 75, 100, 120... Should I just short the plug and see what happens? My light should just go on.

Note: it looks like 18 AWG stranded like you would find in a typical computer power cord. This is rated.to handle 16 Amp. The switch and plug socket also are rated for 15 amp. I doubt I would ever get close to that with a bulb in the socket. Even a 120 watt bulb would let only 1 amp through.

The TV is rated 30 watts so it will draw 1/4 amp when it settles down after startup on the initial rush current? A 25 watt bulb will barely let it run steady state but a 40 watt should limit the initial current to 1/3 amp.

[Shock]

Don't screw any insulation material into the terminals it's a bad electrical connection and will split the insulation exposing more of the wire outside the terminal. When you have a screw post terminal you twist your exposed wire, then make a loop with typically around 10mm wire. You loop in the direction the screw tightens so it will clamp down on it well.

Of course none of what you have there is to any safety standard. I would have used proper double insulated mains wire, instead of that cheap cable. But it looks like it will get the job done.

Not an adequate test for mains wiring (which is why you need to make sure your terminations are good), but for a quick test before powering up you can use your multimeter on ohms range to test from the 3 plug pins through to the socket to check your polarities. e.g. which pin on the plug goes to which socket hole. A beginners mistake is wiring the plug and socket the same looking at them front on.

Yes a short will test it. What watts work depends on how you use it. With LCD TVs/monitors the SMPS just needs to go into standby at first. The bulb will initially go brighter with the inrush current but it dims as the current draw from the SMPS settles down. I can't see it hurting to use a lower wattage bulb first for the SMPS (more reactive) then moving up.

This video shows how it works with fairly consistent loads.

[tautech]

If you are wondering how to house your dim bulb tester, check this old post of mine:
https://www.eevblog.com/forum/repair/suggested-for-a-sticky-part-one-comments-or-additions-please/msg470686/#msg470686
Just an old PC PSU case.

[Shock]

Tautech yours is very ghetto I might knock a permanent one up over Christmas to see what I can make on a budget.

[edy]

Thanks for the advice... I will stick in a bulb and check the continuity and resistance across my 3-prong plug and the socket. I have stripped 1 cm and coiled it around each screw clockwise so as I tighten the wire wraps around even more. The only variation is the ground wire to the box of the light switch.... Instead of cutting it I just stripped about 15mm on the part next to the screw and wrapped it full circle around the screw, then continued the green wire to the box for the outlet.

So I will make sure there are no shorts across any of the wires and/or grounding before I plug it in. Now about the wire gauge, it is computer cable that should be able to power a power supply rated 300-400 watts. Even a small 240 watt system would maximally pull about 2 amp? So the cable has got to at least handle 2 amp. I will never use a light bulb greater than 120 watt so even a dead short through the outlet device would be limited by the bulb at 1 amp. Isn't this ok then?

Just one question, even the bulb has an in rush current that could be 10-15x the steady current draw until the filament heats up. So for a 60w bulb could be as high as 7.5amp. I realize the TV has a thermistor which can dampen that... but the dim bulb tester doesn't.

[tautech]

Tautech yours is very ghetto I might knock a permanent one up over Christmas to see what I can make on a budget.

Sure, but it spends most of its time on a shelf, however it is indespensible when needed.
One could have made it more flashy...extra sockets for storage of other value bulbs etc.
One needs probably 3 wattages for most needs, but then it get big. 
How mine is now, small and the leads are removeable is perfect IMO.

For the OP, use it on various bits of gear to understand how it behaves on power on.
Learn to realise the current draw behaviour of different PSU's in different gear.
If all is well, a linear PSU will make the bulb flash briefly as a result of transformer magnetising current whereas a SMPS will flash more brightly while the main caps are charging.
It limits inrush and operational current drawn, the intention is to keep the magic smoke in. 

[Shock]

Edy, it really makes no difference operationally, I would have avoided dangling wires out like that with no strain relief.

Someone tried some math on the subject here read this post.

As far as I can tell the inrush current of the bulb should be less evident as the SMPS and the bulb counteract each other while powering up. There is a lot of variables at play, perhaps W2AEW (Alan) can do a video and clear the mysteries of the dim bulb tester once and for all, I'll send him a message.

[edy]

Ok, I decided to beef up my wires as per your suggestions... Picked up some 12 AWG. The photos show the upgrade. Basically I have the black from the plug spliced through the switch and bulb socket to the outlet (I cut it in 2 places along the way without cutting the ground or white and just tie it to the switch and bulb socket). The white wire returns back to the plug as one continuous piece. The ground is also continuous and I have it looping through both screws on each box and the green ground screw on the outlet. That has got to be overkill now... I'm sure it will handle quite higher amps than ever thrown at it.

After testing all paths and confirming no shorts or swapping hot/neutral I plugged in a shorted cable in the outlet and flipped on the switch to light up the 25 watt bulb. The cold bulb measures 48 ohm resistance but should be significantly more to reduce the current to only 0.2 amp after lighting. My calculations say is should be ~600 ohm... if V=IR, V/I=120/0.2=600 ohm and power is then P=VI=120x0.2= 24 watts.

That means when I first turn on the bulb I may have an inrush current of 120v/48 ohm = about 3 amp, which then settles to about 0.2 amp. I'll test out my other bulbs but suffice it to say I think the 12 AWG should handle it now.

[edy]

Holidays came early! My parts have arrived... that cap just exudes quality. Don't know how I'm going to get that SMD component on there though.... might have to sharpen my soldering iron.  . Sorry about the rotated images, my phone app that I use to compress them for upload does something weird and when I rotate them back they bloat in file size again.

[edy]

My electronics tester arrived today from China! This thing here:

http://www.ebay.com/itm/NEW-Versio-Transistor-Tester-Diode-Triode-Capacitance-LED-ESR-Meter-MOS-PNP-NPN-/301159202930?pt=LH_DefaultDomain_0&hash=item461e7cc072

Looking forward to trying it out on the remaining parts on my TV and reporting back here on the progress... Just need a bit of free time over the holidays to play with it!

[edy]

I'm working on replacing the parts and I am confused as to D608 replacement, and also D607. The original parts were BLACK with a GRAY stripe, labelled IZB36 BL and IZB27 BL and looks like a regular diode like you'd see for the 4 rectifying diodes. However, I assume it is a Zener as it is labelled IZ. The replacement parts from ShopJimmy are smaller and orange colored with a black stripe, and labelled U7 53A IN (as far as I can see) which look like a typical Zener.

Is this just a manufacturer difference? I can't find the exact part number of the new part online but it looks like it should be it. I also tested the old diode part on the "MTester" and found it was showing up as a resistor (it was a dead short remember), whereas the new diode part was correctly identified as a diode.

[edy]

Success!!!! Thanks everyone!   

So I ended up replacing ALL components that were provided in the Repair Kit (all 13 of them), as I knew already 3 or 4 were faulty on the board and then I figured I'd just unsolder the remaining ones since I had replacements anyways. In the process I found a few more bad ones.

Here are all 13 components provided in the kit and which ended up being BAD or GOOD on the board:

1 Resistor  (R611 *BAD)
3 Transistors (Q501  *? can't test it , Q601 *BAD, Q602 *BAD)
8 Diodes   (Bridge Rectifier: D601, 602, 603, 604, *all GOOD)
                (D607 *GOOD, D608 *BAD, D609 *BAD, D653 * BAD)
               (by the way I would have never suspected D609 or D653)
1 Capacitor (C605 * PROBABLY GOOD but I changed it anyways)

As you can see by the attached images, I used the DIM BULB TESTER which I made thanks to your help here on the forums. I started off with a 25 WATT bulb.... Light went on for a second then off.... And TV was trying to "boot" but would not start (status light would power up, then off, then on, then off and show "Philips" for a moment on the LED screen).

Then I went up to a 40 WATT bulb... same thing... Bulb on and then off a split second later, and TV looked like it wanted to start but would cycle on/off the screen with the startup logo.

Finally, placed a 60 WATT bulb and TV powered up!!! And the bulb had a faint glow on it, as you can see by the attached photos. The TV ran well and I'm using it now.

All in all....

$5 in blown fuses
$25 in parts/shipping from ShopJimmy
$15 for the ESR/component tester
$25 for parts to build Dim Bulb Tester
A whole bunch of time troubleshooting...
------
TOTAL: $70

Learning a ton of concepts on electronics repair.... PRICELESS!

(By the way, my wife couldn't wait for me to fix this thing as she needed it at her office... so meanwhile I bought another TV of the same size for $135... so this repaired one will be an extra we needed for home anyways).

[edy]

Hi folks, Just wanted to let you know I shared my story with Shopjimmy and mentioned EEV BLOG here:

https://www.shopjimmy.com/repair/share/story/id/262/issue/Philips-22PFL4907-F7-No-Power/

[Vito_R]

Congrats on your successful repair.   

[edy]

Hi everyone,

I've made a SUMMARY VIDEO of the entire repair here. Thanks again to everyone for their help:

[miguelvp]

Nice video, concise and to the point

[edy]

I looked up your part number and found this:

http://www.shopjimmy.com/catalogsearch/result/?q=EAY37228901

Is this it? The site lists a bunch of parts and substitutes so perhaps one of those will have a schematic available to download, or you can source parts or kits for repair.

Also check here for service manual:

http://www.eserviceinfo.com/downloadsm/37727/LG_32LC7R--32LC51--32LC52.html

And look here:

http://www.scribd.com/doc/48670580/LP78A-Ch-32LC7R-32LC51-32LC52#scribd

The document you are looking for is titled "LP78A Ch_32LC7R_32LC51_32LC52_.PDF". Sometimes you do a bit of investigation on Google and even though you can't find the manual it will let you find other search terms that you can look for and then you search using them.

I downloaded the PDF on Scribd and have confirmed it contains schematics, part numbers of all boards, with block diagrams and so on. It is a service manual. I will try to break it up and post it here.

[edy]

Here are the first sections (I had to split it up into 5 page segments due to upload size limits).

[edy]

And now the next chunk of pages.

[edy]

Here's the final part of the service manual... lots of schematics.

[Vito_R]

I replaced a fuse in a broken TV I have, and the NTC thermistor blew its arse out in spectacular fashion. So the advice about not just replacing the fuse is worth following.

Would a 200 Ohm resistor made out of a chain of 10x 20 Ohm 5W resistors be satisfactory for discharging power supply capacitors? A 400V cap would discharge at a peak of 2A. Which is a peak of 800W, but would it be for short enough time for the resistors to handle. I have such resistors on hand. I have heard a light bulb is also a good method. I'm too chicken to be shorting them out with a screwdriver.

The 200ohm resistor should be fine.  I usually use a 100 ohm 10watt resistor to discharge caps with 2 insulated alligator clips on each end.  Don't short them out with a screwdriver, that can potentially damage other parts on the board in certain situations.