Author Topic: Sourcing a replacement transformer, LCD TV repair.  (Read 5451 times)

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Offline mreguy

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Sourcing a replacement transformer, LCD TV repair.
« on: June 09, 2018, 10:38:18 am »
Hello,

A friend gave me a lovely LCD tv that does not work (Toshiba 55WL800A). He said that it made a pop and a fizz and did not turn on again. So I took it home and took it apart.
The power supply board (PA-3241-01TS-LF) has a component on the 240v side that is charred (T101) but otherwise looks to be in good condition (I assume that this was the fizz and not the pop). I feel confident that I could change the part however I don’t know what it is (I assume it is a transformer), how to buy one or if it was a secondary failure and I still need to find the primary failure.
I hope to watch a few YouTube videos and learn how to test some of the components on the 240v side of the board. A google search has not revealed anything useful about the charred component.
Does anyone have any idea on what the part is or where to buy one? Can I get any advice on looking for further failures and doing testing prior to reassembly?
Thanks
Steve


 

Offline coromonadalix

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #1 on: June 09, 2018, 11:00:04 am »
you better find a new psu board  instead of searching this part ???   ask your local electronic repair if you can order this part alone ??? sometime the board will come as a single part, no other parts will be available ...


there's one on ebay :  300km of my home

https://www.ebay.com/itm/Toshiba-47-47TL515U-55-55SL417U-55TL515U-PA-3241-01TS-LF-Power-Supply-Board/202326954240?hash=item2f1ba05100:g:RS0AAOSwuHdaVChX
 


Offline mreguy

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #3 on: June 09, 2018, 11:11:33 am »
Thankyou coromonadalix, but why is it not worth repairing this board? is this component a hens tooth? I will keep those links in mind but I was hoping to repair the board on the cheap. Thanks again.
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #4 on: June 09, 2018, 11:12:17 am »
There is nothing wrong with that transformer. How do you think corner of ferrite could even char like this. Look at C115.
 
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Offline mreguy

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #5 on: June 09, 2018, 11:20:21 am »
WOW thanks for that insight wraper,  I have basically no experience repairing electronics so I thought that it was possible for the transformer to melt / Char. It does look to me like c115 exploded. I will take a closer look at it when I get home. Do you know what kind of cap that is, are they likley to be able to reccomend a replacement at my local electronics shop (Jaycar)?
 
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Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #6 on: June 09, 2018, 11:25:11 am »
330pF 1kV ceramic. Although I would not be surprised if it also caused some semiconductor devices around it to fail, like Q100. Also F601 fuse might be blown as well.
« Last Edit: June 09, 2018, 11:36:44 am by wraper »
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #7 on: June 09, 2018, 11:35:39 am »
I checked Jaycar catalog and the only high voltage cap I found is 10n 3kV. So It seems you'll need to buy it somewhere else.
 

Offline mreguy

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #8 on: June 09, 2018, 11:41:33 am »
Thank you so much Wraper,  Is fuse 601 the one at the bottom left hand side where the AC comes in? How do you remove that style of fuse? do the holder and lead form part of the fuse, meaning I desolder it?  I will get the multi meter out as soon as I can and look at the components. I will get back to you with what I discover :-)
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #9 on: June 09, 2018, 11:50:18 am »
F601 is a black rectangle close the the charred transformer. It is soldered in, of course you should first measure continuity without removing it. In any case, it would be useful to check all other fuses as well. Just be aware that high voltage electrolytic capacitors (C111 - C114) may remain charged for quiet some time even after disconnecting PSU from mains. So be careful. Either measure the voltage on them with multimeter before touching anything or discharge them.
« Last Edit: June 09, 2018, 11:54:49 am by wraper »
 

Offline mreguy

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #10 on: June 09, 2018, 11:54:30 am »
Wow thank you. I did not know that was a fuse.
 

Offline mreguy

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #11 on: June 09, 2018, 02:00:21 pm »
I am in the newcastle area. But if I get stuck I will give them a call. Thank you.
 

Offline Rasz

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #12 on: June 10, 2018, 02:51:11 pm »
you better find a new psu board instead of searching this part

good advice when replacement is in $50 range, $100 imo makes it not economical, brand new TVs are ~$200 nowadays
it should be $50, like here http://rtv-oborniki.com/zasilacz,B3QM.html and http://zalewskirtv.pl/czesci-elektroniczne-pa-3201-01ts-lf-v71a00021700.html in Poland
https://www.ksp-electronics.com/en/product/view/39658-power-supply-pa-3201-01ts-lf-v71a00021700 Bulgaria
https://spares2repair.co.uk/toshiba-42vl863-power-supply-v71a00021700-rev-05-pa-3201-01ts-lf-rev.-b-787902-tc22932d3 UK
https://electropartsonline.com/toshiba-42-42sl417u-42tl515u-46sl417u-pa-3201-01ts-lf-lcd-power-supply-board $68 US

but why is it not worth repairing this board

its not about the value, its about required skill. As you said it yourself 'no experience repairing electronics', you didnt even recognize a fuse :(, SMPS are not something you learn electronics on. This will have popped mosfets/diodes/controller/driver ICs/maybe even discrete components

PA-3201-01TS-LF
IC601 A6069H stby
IC100 FAN7930 PFC
IC301 FSFR1*00

similar toshiba/liteon supply diagram https://www.electronica-pt.com/esquema/lcd/pe-3850-01un-lf-power-supply-toshiba-33343/


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My fireplace is on fire, but in all the wrong places.
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #13 on: June 10, 2018, 03:25:27 pm »
Looking at schematics provided by Rasz as reference (seems like lower power version with half number of the transformers), if R120/R121 survived, then C115 failing might be just it, without other serious consequences. F001 fuse likely is gone, RT001 might fail as well but likely isn't. BD001 experienced some stress but, I guess, should be fine.
 

Offline mreguy

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #14 on: June 10, 2018, 07:22:34 pm »
Thanky you for your help Raz,
The replacement boards that I have been able to find are $150 by the time you factor in shipping etc. So I was a bit reluctant to gamble that much it even if it is a nice TV. As you say a smaller much more modest tv can be had for $200. I understand this isn't an ideal project to work on, but the TV is already broken so as long as I don't get a shock and or the house doesn't burn down I can live with the result.

Wrapper,
Thank you again for your invaluble help!! I have checked BD001 and it is good. There is continuity across F601. F001 is gone like you say. I will double check the others. C115 is in the mail.
I will keep you posted on my progress. 
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #15 on: June 10, 2018, 07:32:19 pm »
Check if R120/R121 (they are in parallel) have low resistance in the region of a few ohms maximum. If they are fine, It should be quiet safe to replace capacitor and fuse and then just power it up.
 

Offline Rasz

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #16 on: June 10, 2018, 08:35:36 pm »
its 400v DC, so instead of getting shocked you can get fingers glued to the PCB while your blood slowly boils :)

I would also remove middle radiator and check transistors, and measure transformers in pfc circuit
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My fireplace is on fire, but in all the wrong places.
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #17 on: June 10, 2018, 09:40:07 pm »
I would also remove middle radiator and check transistors, and measure transformers in pfc circuit
That capacitor is basically parallel to rectified mains voltage (with PFC transformer and R120/R121 in series). It's unlikely that something else failed. There is no reason why MOSFET should fail. That could only happen if R120/R121 failed open. And that's why I suggested to check them.
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #18 on: June 10, 2018, 09:53:13 pm »
You probably should check if source-drain of Q100 is not shorted (after desoldering/replacing C115), just in case. Bet there is no need to remove the heatsink for that.
 

Offline mreguy

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #19 on: June 12, 2018, 01:03:32 pm »
Thanks again Wrapper, F001 has been replaced. RT001 has continuity, R120 and 121 show around 0.2 Ohms out of circuit (my $20 MM didn't give a stable reading but stayed in that area). I will pop C115 back in when it arrives, check source to drain on Q100 and Q101 and then put it back together. I will post the results.

Rasz, I didn't realise that could happen, but I have zero intentions of working on a live circuit. I will be plugging it into the mains for the first time when the cap is replaced and the TV is reassembled. Even then the tv will be outside on cement and I will be far enough away for it to be safe. The TV is double insulated and I have a RCD installed on the property. Thank you for your concern.
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #20 on: June 12, 2018, 01:33:09 pm »
Wear some eye protection when you turn it on. Just like that cap had its arse blown out I had a NTC thermister do the same and it made a nice little shower of sparks and I can see where little bits are embedded nearby.

Like you I don't have much TV repair experience. So I don't know if it is rare or common for such things to happen. Better safe than sorry.
I often place the PCB on the side with components downwards, LOL.
 

Offline mreguy

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #21 on: June 26, 2018, 08:52:37 am »
Woo Hoo, thank you so much everyone the help. I replaced C115 today and I had previously replaced the fuse. It worked first time I pluged it in  ;D
 
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Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #22 on: September 25, 2018, 06:44:28 am »
hello i have a problem a tv toshiba model 46ul863 with power supply board pa-3201-01ts-lf.
the power card had ic601 exploded. I replaced it but now there is no power you have pin 3-5 of the ic 601.
I checked and I have no power even you have 6-8 pin of the IC100.
I have 320volt in c111 / c112 / 113.
I thank you in advance and I apologize if I have not written very well.
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #23 on: September 25, 2018, 08:29:26 am »
I have no power even you have 6-8 pin of the IC100.
Pin 6-8 of IC100 or IC601? Because first makes no sense. Check voltage on primary winding of T601, also check it's resistance. There is a chance that winding blew up as well.
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #24 on: September 25, 2018, 08:32:53 am »
I don't see it in schematic of similar PSU from Rasz but check F601 fuse which is near to FB601.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #25 on: September 25, 2018, 09:28:20 am »
the f601 fuse is ok.
in pins 3-5 of the ic601 there is no power supply.
what are the legs to check on the part of the primary? on the part of the primary there are 5 feet
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #26 on: September 25, 2018, 09:35:05 am »
looking at the tracks from f601 it goes through fb601 then goes to pin 5 of t601.
between gnd and pin 5 of t601 I have 320v
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #27 on: September 25, 2018, 09:57:05 am »
what are the legs to check on the part of the primary? on the part of the primary there are 5 feet
One leg which goes to FB601, another which goes to IC601. If there is no power on pin 5, then first check if there is no short to ground. Then check components connected to it. As IC blew up, very likely there was high voltage applied to that pin through IC and something could blow up as well.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #28 on: September 25, 2018, 10:10:32 am »
on the foot connected to FB601 and the ic601 there is no power supply.
pin 5 of ic601 is not short-circuited with gnd
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #29 on: September 25, 2018, 10:15:58 am »
on the foot connected to FB601 and the ic601 there is no power supply.
I was meaning measuring winding resistance between those points.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #30 on: September 25, 2018, 10:20:53 am »
sorry, about 1.5 ohm
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #31 on: September 25, 2018, 10:24:38 am »
is it normal that there is no power supply to pin 5? who gives him power?
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #32 on: September 25, 2018, 10:35:07 am »
is it normal that there is no power supply to pin 5? who gives him power?
First small current is provided through R630, R631 from high voltage (path 1). This is so standby PSU can start, when it starts, then it powers itself fro auxiliary winding of T601 (path 2). If voltage on pin 5 never rises, either those resistors or R609 are open or something leaks the current to GND so voltage never rises.

 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #33 on: September 25, 2018, 10:36:52 am »
sorry, about 1.5 ohm
winding should be ok.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #34 on: September 25, 2018, 10:50:43 am »
before R630 I have 78v, between R630 and R631 I have 38v, between R631 and R609 I have 38mv
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #35 on: September 25, 2018, 11:29:04 am »
Well, something is leaking current to ground.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #36 on: September 25, 2018, 12:04:25 pm »
I removed ic601 but at pin 5 I have 0.8v.What should I check?
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #37 on: September 25, 2018, 12:25:51 pm »
First of all semiconductors connected to it, capacitors as well. I would start with ZD604, C613, D603. Just note that you should not power it on without ZD604 as something else may blow up due to possible overvoltage, or temporarily replace it with say 12V or similar zener diode and power on. You could also remove R607 to disconnect a large part of the circuit (to exclude it as a cause), just do that with IC601 still absent from the circuit.
« Last Edit: September 25, 2018, 12:27:24 pm by wraper »
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #38 on: September 25, 2018, 01:06:06 pm »
I removed ic601 from the board, to the pin ho0,8v, I replaced c613, I removed R607and I still have 0.8v to pin 5.
I checked zd604 and d604 but both of them are not open and are not shorted. do you advise me to replace them anyway?
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #39 on: September 25, 2018, 01:07:32 pm »
I try to take off the R616?
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #40 on: September 25, 2018, 01:14:06 pm »
I try to take off the R616?
It won't change anything. It's part of the circuit you should not bother with.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #41 on: September 25, 2018, 01:20:34 pm »
what do you suggest me?
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #42 on: September 25, 2018, 01:22:48 pm »
I try to take off the R609?
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #43 on: September 25, 2018, 01:24:34 pm »
I removed ic601 from the board, to the pin ho0,8v, I replaced c613, I removed R607and I still have 0.8v to pin 5.
I checked zd604 and d604 but both of them are not open and are not shorted. do you advise me to replace them anyway?
If you removed R607 and problem still remains, you have a very small number of parts remaining. Diodes and zener should properly check as diode, conducting in one way only.
You could also remove D603, just in case it's leaky. And then remove remaining components one at a time and check how it works. Just as I said, replace ZD604 zener with something else to avoid damage by over voltage. If you don't have any, take ZD605 and place it instead of ZD604 temporarily.
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #44 on: September 25, 2018, 01:25:10 pm »
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #45 on: September 25, 2018, 02:13:52 pm »
Yes, the diodes control them in diode mode and lead only one way. I removed the zd 605 and put it in place of the ZD604. I removed D603. now in pin 5 I have nothing, I have 13v between R631 and R609
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #46 on: September 25, 2018, 02:23:05 pm »
I have 13v between R631 and R609
I don't really get it. They are directly connected together, how there can be 13V between them?
EDIT: I guess you mean 13V between point they connect and GND.
« Last Edit: September 25, 2018, 02:25:07 pm by wraper »
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #47 on: September 25, 2018, 02:26:55 pm »
If you have 13V on one side of R609 and zero on other, then R609 would need to be failed open. But it contradicts previous measurments.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #48 on: September 25, 2018, 02:35:08 pm »
yes I mean 13V between point they connect and GND.
what value should the R609 have?
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #49 on: September 25, 2018, 02:39:03 pm »
putting the ZD604 and ZD605 back to their original position I find on one side of the r609 I have 13v and on the other side 0.9v
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #50 on: September 25, 2018, 02:43:51 pm »
putting the ZD604 and ZD605 back to their original position I find on one side of the r609 I have 13v and on the other side 0.9v
This completely contradicts with:
Quote
before R630 I have 78v, between R630 and R631 I have 38v, between R631 and R609 I have 38mv
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #51 on: September 25, 2018, 02:45:16 pm »
Did you check ZD605 BTW, isn't it shorted by chance?
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #52 on: September 25, 2018, 03:15:07 pm »
Also write part number of IC601, I don't know what it is.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #53 on: September 25, 2018, 03:18:20 pm »
I had to get out of work. I will resume tomorrow. Thank you very much for your information and your patience. We'll talk tomorrow. good day
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #54 on: September 25, 2018, 03:21:40 pm »
Ic601=A6069H
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #55 on: September 25, 2018, 03:28:45 pm »
In R609 there is written 625
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #56 on: September 25, 2018, 04:04:33 pm »
Ic601=A6069H
I checked the datasheet. It's strange they placed R609 at all. Seems it has 6.2M resistance. This IC actually takes startup current from pins 7,8 and pin 2 is for voltage detection only. Thus placement of R609 is weird but as it has a very high resistance it basically does nothing. As you said there was 38mV on pin 2 when IC was present, I assume that IC is either faulty ir you got counterfeit with something else inside. Where you bought the replacement IC?

http://www.semicon.sanken-ele.co.jp/sk_content/str-a606xh_ds_en.pdf
« Last Edit: September 25, 2018, 07:03:04 pm by wraper »
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #57 on: September 25, 2018, 04:51:29 pm »
Tomorrow I replace the components that I had removed each of their original poto and recheck. Honestly Ic601 after being exploded did not read what was written. It read only A .... H Then on the web I found it was A6069H. Actually I do not know if it's correct
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #58 on: September 25, 2018, 10:32:49 pm »
Try measuring resistance between pin 2 and 3 of the IC.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #59 on: September 26, 2018, 06:16:46 am »
Good morning, I checked the schematic of the power card you sent me and it corresponds to my card. I put all the components back to their initial position. now without ic601 I have between GND and before R609 13v, between GND and after R609 i have 0.9v. I checked the schematic of the A6069H and it seems to me that the GND is the pin 3, and the Vcc is the pin5. is it correct? between pin 2 and pin 3 I have about 1Mohm. between GND and pin 7/8 of IC 601 of the board I have 320v
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #60 on: September 26, 2018, 10:40:25 am »
putting the ZD604 and ZD605 back to their original position I find on one side of the r609 I have 13v and on the other side 0.9v
This completely contradicts with:
Quote
before R630 I have 78v, between R630 and R631 I have 38v, between R631 and R609 I have 38mv

I have 0.9 without ic601 installed, and I have 38mv with ic 601 installed
 

Online wraper

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #61 on: September 26, 2018, 11:35:05 am »
it's a bit confusing what you wrote in last 2 messages.
 
Quote
now without ic601 I have between GND and before R609 13v, between GND and after R609 i have 0.9v.
What do you have before R609 with IC installed?
 

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #62 on: September 26, 2018, 12:10:09 pm »

with ic installed, before R609 i have 38mv
 

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #63 on: September 26, 2018, 12:23:37 pm »
Pin 2 is input, so it should not pull voltage down this lot. It has a 6.4V zener diode on it so it what it should be limited to. 38mV certainly seems as indication that IC is either faulty or counterfeit.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #64 on: September 26, 2018, 12:38:14 pm »
ok, I will get another one. if this has burned up there is still something wrong with this card? I removed ic and in pin 2 I have 13v but in the 5 i continue to have 0.9v. Is it normal?
 

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #65 on: September 26, 2018, 01:32:34 pm »
ok, I will get another one. if this has burned up there is still something wrong with this card? I removed ic and in pin 2 I have 13v but in the 5 i continue to have 0.9v. Is it normal?
Yes, it's normal. Unless there is something wrong with parts connected to pins 7,8, it should not fail. And if it fails, most likely it will blow up. Hence I suspect counterfeit, there are plenty at shady sources.
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #66 on: September 26, 2018, 02:11:47 pm »
can you advise me where to buy it?
 

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #67 on: September 27, 2018, 02:24:48 pm »
good morning, when I get ic new, can I check it somehow before installing it?
 

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #68 on: September 27, 2018, 03:25:34 pm »
just solder it in
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #69 on: September 28, 2018, 05:58:27 pm »
hi, I replaced ic. now I have 5v, but there is a problem in the PE0982 tab V28A001292A1. because when I connect it I'm 5v volts to 0. Is there a short circuit in the part of 5v. Is there a datascheet for this card?
 

Offline boba3

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Re: Sourcing a replacement transformer, LCD TV repair.
« Reply #70 on: October 04, 2018, 06:44:50 pm »
hello,
the board at the desk, in addition to having 5 volts must have other power supplies?
 


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