Basic Fuse Question Philips TV

[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!