Re: Rca l37wd12 lcd tv
I got my replacement main board today, installed it and am now posting this from the working TV. I'm using it as a 37" computer monitor since I didn't bother replacing the analog tuner connection which has been snapped off.
All I wanted it for was to use as a computer monitor and that's what it's doing!
Total cost ~$80 CAD
gelatinous
Member
Last Activity: 01-22-2014, 07:17 PM
Joined: 05-06-2012
Location: Victoria BC
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Re: Rca l37wd12 lcd tv
no worries budm,
I found a used main board on ebay that I have ordered. no rush for the schematic right now, though if the replacement doesn't work I may ask again.
Thanks for looking for me!Leave a comment:
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Re: Rca l37wd12 lcd tv
any luck budm?
I'm trying to source a main board in case I can't repair this, but they aren't very plentiful.Leave a comment:
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Re: Rca l37wd12 lcd tv
thanks for checking!Leave a comment:
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Re: Rca l37wd12 lcd tv
I hope to be ordering an ESR meter soon so that I can try and test some of the SMT caps on the mainboard.
budm, would I be able to pester you about a schematic for the scaler board if there is one?Leave a comment:
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Re: Rca l37wd12 lcd tv
just bumping this back up. I haven't had a chance to trace the button line yet, I will hopefully be doing that tomorrow evening.Leave a comment:
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Re: Rca l37wd12 lcd tv
I know that there's one 2.5V supply on the board and it is active when the system is in standby. It is also the voltage used to run the keyboard buttons..
I will post the pictures of the scaler board shortly, they are still on my phone....Leave a comment:
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Re: Rca l37wd12 lcd tv
thanks budm!
With these diagrams I have determined that pin 2 on the keyboard is just high enough to enable TK002, which in turn disables TK001 which in turn turns off the standby LED. So once again this is pointing to a main board issue as pin 2 connects to the main board.
I will hopefully be able to trace this line soon, though I have a feeling that it is going to run to the same processor as the TV_KEY and the P-ON signals.Leave a comment:
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Re: Rca l37wd12 lcd tv
Thanks budm, I've registered and am waiting to be able to login. When you get a chance would you be able to check the button board schematic and see what the two SOT23 parts are?Leave a comment:
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Re: Rca l37wd12 lcd tv
Thanks budm, the layout of your tv looks identical to mine. can I ask where you found the service manual? I've been looking but haven't had much luck.Leave a comment:
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Re: Rca l37wd12 lcd tv
I think I may have found a problem on the button board. I can't tell if this part is a transistor or a double diode... If my memory is correct the part is labelled TK002 and is SOT23 packaging
Pins:
1
23
Diode check:
2-3 ........1807....... OL
1-2 .........OL.......OL
1-3 .........OL.......OL
in board and out of board. So far as I can tell this part has to do with the standby LED, it may have more function but I haven't looked at the circuit that close. I wish I'd brought the board with me...Leave a comment:
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Re: Rca l37wd12 lcd tv
Ok, I jumpered the 5V standby to the P-ON and the relay clicked and voltages came up. 12V was 11.7V 24V was 23.9V. Power LED turned green. No Backlights were present... Inverter voltage was ~2V.
The main processor that the button signals go to had 1.8V and 3.3V when in standby but no standby LED was present.
I am inclined to say that this is a main board issue and that it is going to take a while to troubleshoot.Leave a comment:
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Re: Rca l37wd12 lcd tv
yes the unit does not power on at all. However, I think that this is because the PSU is not seeing the 5V P-ON signal from the main board, telling it to turn on. The main board is not generating this signal at all.
When I first got this TV plugging it in a leaving it for a while, then quickly unplugging and replugging it in would turn it on, but all buttons would be unresponsive.
Since working on the 1W board the unit now does nothing. The 5V standby is still getting to the main board and I can measure ~160V at...Leave a comment:
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Re: Rca l37wd12 lcd tv
I had no sound from the PSU at all when it was connected. Before I replaced the cap on teh 1W board I was able to hear a high pitched squeal from the 1W board, but the PSU itself has always been silent.
I noticed that the 5V signal to engage the relay on the 1W board is connected to the P-ON signal to the PSU via a zero ohm resistor on the main board. I have also traced the signal to a pin on one of the micro processors, there appears to only be a 100ohm resistor between the microprocessor and the 5V enable. I hope to be able...Leave a comment:
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Re: Rca l37wd12 lcd tv
I've replaced all the output caps as they were bulging, the TV did exibit the same symptoms after though, it's only been since I worked on the 1W board that it stopped turning on at all... I still get 5V standby to the mainboard, but even bypassing the relay on the 1W board gives me zero output on the PSU now. The inline fuse on both the 1W board and the PSU are good.
I will have to snag some wire from work so I can measure across the startup cap....Leave a comment:
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Re: Rca l37wd12 lcd tv
Here are some shots of the PSU, I noticed that there is a section on the bottom that looks to have gotten hot, looks to be one of the transformer windings.
I tried changing the startup cap 10uF 50V on the PWM PFC chip but that had no effect.
It's hard for me to measure the voltages on this supply as it has to be in the TV for me to power it up... I don't have a good selection of testing cables at my house. I was able to measure ~160VDC at the output of the bridge though.
EDIT: I just noticed that my attachments are messed...Last edited by gelatinous; 06-02-2012, 11:23 AM.Leave a comment:
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Re: Rca l37wd12 lcd tv
Sorry I haven't had a chance to do anymore work on it yet. I've been busy with other projects and teaching a friend how to drive.
I will try and get some pictures of the power supply and main board either tonight or tomorrow.
My TV currently does nothing if I bypass the 1W board with some seizer clips, I don't measure any voltage out of the supply at all....Leave a comment:
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Re: lg plasma interference from blackberry.
I've noticed that cell phones using GSM interfere a lot with audio products. While I've never had picture break up I have had buzzing and beeping noise when my phone is withing a few feet of a speaker. This happens in my car as well, if I have weak signal strength the phone will interfere with my car stereo. I have only had the happen with GSM phones and not with a CDMA based one.
my blackberry curve did it, so did my friends and my current Galaxy S Captivate also does it.Leave a comment:
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Re: Rca l37wd12 lcd tv
I will try and take some pictures tonight. The lighting at my place isn't very good but I'll see what I can do....Leave a comment:
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Re: Rca l37wd12 lcd tv
I could be wrong, I was going off of the interconnect diagram that was posted in another thread. I'll have another look and see.Leave a comment:
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