Sanyo DP42740 Short on Main Board?

[caphair]

Re: Sanyo DP42740 Short on Main Board?

sorry just realised this is a plasma so doubt if its eeprom related did you read this thread not sure if its the same issues your having
https://www.badcaps.net/forum/showth...=Sanyo+DP42740

That's interesting poster had same tv and same symptom but ended up being the SN board that fixed it. How's that make any sense? Lol

Wonder how I could troubleshoot the SN board for this symptom. Nothing seems shorted on it

[vinceroger69]

Re: Sanyo DP42740 Short on Main Board?

sorry just realised this is a plasma so doubt if its eeprom related did you read this thread not sure if its the same issues your having
https://www.badcaps.net/forum/showth...=Sanyo+DP42740

[caphair]

Re: Sanyo DP42740 Short on Main Board?

Disconnect the power supply from all the other boards and jumper PS_ON to 5V Standby using a 1K resistor and check what supplies come up.

Tried that I get all supply voltages

[dick_barton]

Re: Sanyo DP42740 Short on Main Board?

Disconnect the power supply from all the other boards and jumper PS_ON to 5V Standby using a 1K resistor and check what supplies come up.

[vinceroger69]

Re: Sanyo DP42740 Short on Main Board?

do what dick barton says in post 22 first but maybe if eeproms are troublesome on these sets your replacement could be faulty too i guess if board was untested ive no idea my self just a thought i had.

[caphair]

Re: Sanyo DP42740 Short on Main Board?

Need to take a step back.
Describe exactly what the symptoms are now at this time.
Eg. Switch on, backlights / no backlights, picture / no picture etc

Turn on, relay clicks twice power led on then 3 seconds later no power led and turns off. Let's you try 3 times before locking you out until you unplug from mains

[caphair]

Re: Sanyo DP42740 Short on Main Board?

I'm not sure. If the original eeprom was bad and the replacement board wasn't shouldn't it have worked?

[dick_barton]

Re: Sanyo DP42740 Short on Main Board?

Need to take a step back.
Describe exactly what the symptoms are now at this time.
Eg. Switch on, backlights / no backlights, picture / no picture etc

[vinceroger69]

Re: Sanyo DP42740 Short on Main Board?

seems odd it powered up yesterday but not today do these sets suffer eeprom issues? would this cause your fault?

[caphair]

Re: Sanyo DP42740 Short on Main Board?

Have you checked if there is a short circuit from VCC1 & VCC2 to 0v on the audio chip itself. There is every possibility that it may have an internal short or low resistance to ground.
If there is a short, can you isolate the track carrying the 15V to VCC1 & 2 using a sharp scalpel to verify if it is the chip or lift the chip?

I measured resistance to ground of both vcc1 and vcc2 pins. Did not read shorted.

Oddly yesterday the 15v was there and tv powered up but there wasn't a picture then would cycle off and back on. Would stay on for 15 seconds then off and quickly back on.

Today I'm back to original problem of it quickly turning off when powered on

[dick_barton]

Re: Sanyo DP42740 Short on Main Board?

Have you checked if there is a short circuit from VCC1 & VCC2 to 0v on the audio chip itself. There is every possibility that it may have an internal short or low resistance to ground.
If there is a short, can you isolate the track carrying the 15V to VCC1 & 2 using a sharp scalpel to verify if it is the chip or lift the chip?

[caphair]

Re: Sanyo DP42740 Short on Main Board?

maybe one or more of the caps from c017 is shorted to GND? Like C020 to C023...
Unplug the board and measure the resistance.

First thing I checked. I don't know what else to look for? I have the 15v from the psu when I turn it on and heck before it powers off I see it momentarily but I don't see the same 15 at the audio power test point when I make same test

[CapLeaker]

Re: Sanyo DP42740 Short on Main Board?

maybe one or more of the caps from c017 is shorted to GND? Like C020 to C023...
Unplug the board and measure the resistance.

[caphair]

Re: Sanyo DP42740 Short on Main Board?

Nothing comes out of the VCC1 or VCC2 pins. It looks like 15V from the power supply feeds those two points from K8B pins 12 &13 as shown on page 23 of the above manual.

Makes sense. Thanks for pointing that out. I traced that line and it goes just through few inductors and resistors. All measure fine. Wondering now if the psu 15v line is the issue when loaded. I turned the psu on with everything disconnected and all voltages tested steady so I'm stumped

[dick_barton]

Re: Sanyo DP42740 Short on Main Board?

Nothing comes out of the VCC1 or VCC2 pins. It looks like 15V from the power supply feeds those two points from K8B pins 12 &13 as shown on page 23 of the above manual.

[caphair]

Re: Sanyo DP42740 Short on Main Board?

Correction: I have all the 3.3v to the ic but nothing out of its vcc1 and vcc2 pins which is what provides audio power. Safe to say the ic is bad?

[caphair]

Re: Sanyo DP42740 Short on Main Board?

So I bought another mainboard off eBay and I have the same issue. Every other board tests fine. I noticed only voltage I don't have on the mainboard when powering on is for audio circuit. But I can't figure out how to troubleshoot it

I have 3.3v to the ic but I can't see where the + on c017 comes from and that's what's missing

[caphair]

Re: Sanyo DP42740 Short on Main Board?

Yes I still measure short across the cap I removed. Not sure if maybe there's an inductor in parallel causing that because the 2 amp draw is completely gone? I haven't checked the voltages on the regulators

[dick_barton]

Re: Sanyo DP42740 Short on Main Board?

Have you checked the voltages on the regulators since removing the chip?

[dick_barton]

Re: Sanyo DP42740 Short on Main Board?

Sorry but I must have misread your previous post. I thought you said you still had a short when you connected the wires back where the capacitor was located after you remove the large chip.