Panasonic TC-32LX85 Dead

[kevinm34232]

When I first plugged it in I heard it click then nothing, no standy light or blink code. Now it's not doing anything. I checked most obvious parts with no sign of a short. I'm getting 120VAC thru the fuse, but I am only seeing about 4VAC between the center pins of the rectifier. Not much info out there on this model, any one have any thoughts?

[budm]

Re: Panasonic TC-32LX85 Dead

https://www.badcaps.net/forum/showth...X85#post341781
See the link for the service manual.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Thanks Bud, I found that thread earlier but that file is not there anymore. I did find the SM and uploaded to Tom's SM email on the site, if that email is wrong Tom let me know please.

Here is a screen shot from the schematic, I get 120VAC and 165VDC at D7001, but the large rectifier D7003 is where I get 4VAC and 8VDC.

[budm]

Re: Panasonic TC-32LX85 Dead

If the relay is not on, you will not get AC feeding the D7003 bridge.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

OK I see that now. So I'm not getting the 5v standby though I'm getting 1.3V.

Bud that SM you show is a different model, this is the correct one, power supply on pages 36 and 37.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Just disconnected the main board connector and the 5V standby comes up to normal, so a problem on the main board right??

[budm]

Re: Panasonic TC-32LX85 Dead

The one in your link matches the chassis?

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Well the PS is the same, the main board is a TNPH0757S which is different. Ill have to check the main board # in the other SM.

[budm]

Re: Panasonic TC-32LX85 Dead

OK, let me download the one from your link and see what the test points to use.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

5vstby is here, something on the main board dragging it down

[budm]

Re: Panasonic TC-32LX85 Dead

can you use 10 Ohms resistor as a 1/2A load to see if will maintain 5V?

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Is that just a 10 ohms resistor attached to 5VSTBY on the PS side but not to anything else?

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

I hooked up my bench power supply and set to 5V and connected to STB5V on main board (removed from TV). I'm just a little unsure of the readings on the PS. The current keeps going from 100mA up to about 400mA and then repeats, is that going into protect from overload?

While it's on I checked the voltages on the DC-DC and got 3.3V and 1.8V from the 2 regulators, so they seem to be working normally.

Does the PS fluctuating current indicate a problem? What should I expect to see for a load? Any tips from here?

Could this still be a problem with the PS? I wasn't clear on how to test with a load on it.

[tom66]

Re: Panasonic TC-32LX85 Dead

400mA sounds ok for a standby rail, at least to start. How much current can your power supply provide? Did you try testing the PSU board like budm suggested, using the resistor?

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Its a 30V 5A power supply. Should it be fluctuating like that though from 100mA to 400+ and then back down, it may be going higher but happening too fast to see.

No I didn't try the resistor I don't know what to, just solder one end of it to the STB5V pin without the main board connected? The other end of the resistor is open? I have a 100 ohm resistor handy will that work?

[tom66]

Re: Panasonic TC-32LX85 Dead

What will a resistor do if the other end is open...? You need to connect it to ground. The resistor is load for the PSU, it will get hot. It needs to be around 10 ohms, 5W rated.

Make sure you've set the current limit on your power supply up from the default.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Ok thanks I found one in an old Y-SUS board.

For this test I'll be plugging the TV into AC without the main board connected, and checking the standby voltage correct?

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

OK so normal voltage without the load is 4.85V, when resistor attached I saw it go up to 3-4V briefly and then drop to 0.13V

Did I set it up correctly?

[tom66]

Re: Panasonic TC-32LX85 Dead

Yep. That's correct, this seems to indicate the PSU cannot supply 500mA load, so I would consider it may be faulty.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Well that saved me a lot of time thanks for that process and thanks Bud for suggesting it.

This is the first time I've run into this problem, is there something in general that would cause it to drop under load?