Dead LG 32PC5RV Plasma TV

[JimsMonitors]

Hi All!
I have an LG 32PC5RV plasma TV that is not functioning. When I power it on, it get an odd buzzing-type noise from the power board for about 2 seconds and then it stops. This is coincident with the green power LED coming on solid for about 1 to 2 seconds and then starting to flash about 16-17 times. After these flashes, the power LED goes red. If I turn the power off then back on, the cycle repeats itself. The power board and the YSUS board look fine (no hot areas, no obvious blown capacitors). I have tried connecting a video/audio source and cycling through the inputs but no audio or video appeared at all. Any idea where the problem might be?
Thank you.
Jim

[JimsMonitors]

Re: Dead LG 32PC5RV Plasma TV

Hi all!
I did some voltage testing and I get a steady 4.95V on the 5V Stby pin. Prior to activating the power button, there is a very low voltage (~0.3 mV) on the other non-ground pins. When I depress the power button, for about 1 second, the voltage on the other pins jumps up to the levels indicated on the PCB. Then they drop back down to zero. I have to wait for about 15 or so seconds before I can try again. This corresponds to the 16 or 17 flashes of the power LED that I mentioned in my previous post. Once the power LED turns red, I can re-activate the power switch and repeat the behavior. Throughout all this, the voltage level on the 5V Stby pin remains steady at about 4.95V. Can anyone suggest any other tests I could try to see if I can isolate where the problem is?
Thank you.
Jim

[Alastair E]

Re: Dead LG 32PC5RV Plasma TV

Check for shorts on Vs line--particularly to the Y-SUS/X-SUS.

Unplug the power cable from X-SUS--does set start up and give sound?--obviously with no picture.

Unplug power leads from Y-SUS, does set start up?

[JimsMonitors]

Re: Dead LG 32PC5RV Plasma TV

Good Day Alastair!
Thank you for taking the time to offer some suggestions.
The Vs line seems fine. I disconnected both ends and there appears to be good continuity on the two individual Vs lines with no shorting between the lines.
Before disconnecting the X-SUS power connector, I checked the voltage levels on the 5V lines going into the X-SUS board. As described earlier, for about 1 second shortly after powering on the set, the voltage level shows at about 4.9V then immediately drops to zero. Same on both 5V lines.
When I disconnected the power connector to the X-SUS board, there was no change in behavior to what I described in my first post. The TV itself produced no sound (i.e. like a power-on "chirp"). It just made the electrical buzzing sound on the power board as described earlier.
When I then also disconnected the power lead from the Y-SUS board, upon powering on the TV, that electrical buzzing sound was no longer present. As well, the green power LED only flashed 3 times before going steady green for 1-2 seconds then turning red. Again, no audio produced by the TV.
Any other suggestions as to what I might try next?
Thank you.
Jim

[Alastair E]

Re: Dead LG 32PC5RV Plasma TV

Hmm--Didnt mean to check like that!

With set off, Check the resistance of the Vs line on Y-SUS plug to metal chassis of set with the PSU disconnected from Y-SUS.

Do the same with the X-SUS....

If a low resistance is found--then that board has shorted IGBT's and or diodes on it....

If no shorts--Whats the Vs Voltage when you first turn set on, everything connected?--Should be around 180-200V

[JimsMonitors]

Re: Dead LG 32PC5RV Plasma TV

Hi Alastair,
Sorry for the misunderstanding. I'm pretty new at all of this.
Here's what I found:
The resistance on the two Vs lines is very high (on the order of 350 Mohms). But it is not consistent. When I first touch the lead to the Vs pin in the connector, the resistance spikes very high and then gradually decreases. The same behaviour happens on both Vs pins in the Y-SUS board connector (with the plug from the PSU unplugged). Similar behaviour and resistance levels were experienced on the X-SUS board, though there is no Vs pin on the X-SUS - just two 5V lines.
When I reconnect all the connectors and power up the set, the voltage level on the Vs lines in the Y-SUS connector max out at 100-110 mV - nowhere near 180-200V.
Thank you for your patience! Any next thoughts??
Jim

[Alastair E]

Re: Dead LG 32PC5RV Plasma TV

Hmm-- You said earlier, the Y-SUS made a very slight buzzing sound...

--IME this would only be present if the Vs was at or around the correct value.

Can you describe exactly How you're measuring the Vs and Va supplies...?

[JimsMonitors]

Re: Dead LG 32PC5RV Plasma TV

Hi Alistair,
The buzzing sound I mentioned is coming from the PS board and only occurs when the cable from the PS board to the Y-SUS is actually connected to the Y-SUS board. And this buzzing is louder than what I would consider to be a normal or acceptable level of electrical buzz on a power board.
When I measured the voltage levels on the Vs lines, I inserted the positive lead into the connector (the end of the cable that attaches to the Y-SUS board) while the connector was still attached to the Y-SUS board. I connected the negative lead to the metal frame. I then applied power to the board (plugged the unit into the mains and depressed the power switch on the front of the TV) and observed the results on my DMM. I also used the MAX function on the DMM to see the level that the voltage got to before the set automatically shut down again after a couple of seconds.
Back to you my friend!
Jim

[Alastair E]

Re: Dead LG 32PC5RV Plasma TV

Well--With no shorts on the Vs line Y-SUS, and no voltage at all when the set is turned on, it could well be the PSU board. The Z-SUS is incorporated on the Y of these sets as far as I can find, the board on that side has just a couple of diodes on it....
--To confirm, a picture of the Y would be good....

What does the pin on PSU marked, 'PS-On' to when you turn set on?