Author Topic: Sourcing a replacement transformer, LCD TV repair.  (Read 5470 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
Who logs in to gdm? Not I, said the duck.
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.
 


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