LG 60PV450 - bad Zsus?

[drbenne]

Hey guys.. looking for some input on this LG 60PV450 plasma

So, initial problem was there was no picture but sound could be heard. Popped it open and looked around for bad caps, didn't see any, they all looked pretty good. No problem there.

Tested all fuses for continuity, found that the fuse on the Zsus board was blown so I removed and inspected both sides of the board. Found also that out of the 3 huge copper inductors, one of the solder joints came loose along with some heat damage. Moreover, the other 2 inductors seemed to have cracked solder joints.
So I cleaned up the burnt solder joint and resoldered all the points to the inductors along with replacing the fuse with the same type (T6.3AH 250V).

Reinstalled the board and connections and turned it on. Still no picture but then came the click, click, click sounds from the relays. The TV would go right back to standby mode.

Disconnected the Zsus board connections, both from power supply and flexible cable from control board. Connected the test pattern jumper and removed the flexible cable from the main board to the control board. Turned it on and was able to get the test pattern to display.. of course it was a red and distorted tint as usually seen from a disconnected Zsus board.

Next, I removed test pattern generator jumper and reconnected the flexible cable from the main board to the control board. Turned it on and was able to get the regular picture display of channel, inputs, etc. (still no Zsus connected, red and blotchy display)

At this point I decided to test the voltages at various points on the Power supply and Ysus board.

Factory Voltage settings:
Va = 55V
Vs = 201V
-Vy = -178V
Vsc = 150V
Vzb = 110V

What I measured:
Va = 55V
Vs = 202V
-Vy = -178V
Vsc = 150V

Testing the Vzb is where my next problem is because once i reconnect everything on the Zsus board, it quickly goes back to the no picture, repeated clicking and standby mode. Holding my meter on the Vzb test point while turning it on also reads no voltage.
I'm almost certain the Zsus is bad but am not sure about the Zsub also.

I've been studying the past 2 days to try and give as much information as possible. I have a background in electronics but this is my first time delving into a plasma TV. Any more suggestions on test procedures, something I missed or a diagnosis would be much appreciated, Thanks!

~Dave

[capkid]

Re: LG 60PV450 - bad Zsus?

Got pics? I'm not sure what you mean by "Zsub" (maybe the Y-Sus?). It looks like your Z-Sus is faulty, but the Y-Sus appears to be fine.

[drbenne]

Re: LG 60PV450 - bad Zsus?

In the pic showing the backside where the coils are soldered, the one circled is the one that completely came loose from the board. I tested for continuity after resoldering and it seems good. The other two obvious resolders tested fine before i resoldered but it was clear that it was beginning to crack. The remaining looked fine to me.

The Zsub is what the Zsus connects to and contains the flexible printed cables that connect directly to the PDP. There are 3 fixed connectors that connect each board. I couldn't find any test procedures to test if that is fine, especially with the Zsus being bad itself.

[capkid]

Re: LG 60PV450 - bad Zsus?

Ah, that makes sense now. It doesn't look like there's much on that secondary board, except for a few caps. Is there anything on the other side? If not, and the caps are fine, I'd probably not worry about replacing it.

[drbenne]

Re: LG 60PV450 - bad Zsus?

There's nothing on the back of the Zsub so im guessing it's fine. I'm just curious as to what's wrong with the Zsus. I'm not sure what happened first, the fuse blowing or the coil coming loose. I'm guessing by the cracked joints that maybe the coil was the first to come loose then blew the fuse but not necessarily instantly.

It's not my tv so I'm not sure what prior symptoms might have appeared before the picture went completely out. I was sure that once i replaced the fuse and resoldered the coils the picture work but it looks like it might've blown something else also.

[capkid]

Re: LG 60PV450 - bad Zsus?

Yeah, based on the gauge of the coil wire, I wouldn't be surprised if something else on the board blew.

[drbenne]

Re: LG 60PV450 - bad Zsus?

Looking at the backside of the zsus again it looks like I found a couple surface mount resistors that look a bit brown. They're connected to the gate of a FGPF4633 transistor which I've never heard of. Looking up the Datasheet they describe them as 330V PDP Trench IGBT. Testing them in circuit yields a short between the collector and emitter also but those are also connected together through an RF2001 fast recovery diode. The collectors also go directly to the connections of the Zsub board.

[ben7]

Re: LG 60PV450 - bad Zsus?

That short could be what is causing the Vzb voltage to go to zero.

Have you tested that diode too?

[drbenne]

Re: LG 60PV450 - bad Zsus?

I tested it in circuit and it's shorting but i'm sure its because of the surrounding circuitry. I pulled out one and tested it by itself and it tested fine. So now i'm thinking the same thing is happening with those 4633s. Unfortunately the 4633s are attached to a heat sink with another set of 3 transistors. I'd pull them out but my soldering iron sucks and it's not doing a good job of melting the solder.

I may just tell this person to grab a new zsus board. I saw a salvaged one on ebay for $50 but Shopjimmy has them for $65 plus the 180 day warranty.

[capkid]

Re: LG 60PV450 - bad Zsus?

ShopJimmy would be my choice if you don't want to take the time to fix the Z-Sus.

[drbenne]

Re: LG 60PV450 - bad Zsus?

Ok, I'm determined to figure this thing out! haha. So pulling back the foam padding on the back side of the zsus allowed me to get a better view of circuitry.

First, I saw that the 3 coils were grounding out which it shouldn't. Pulling back the foam revealed that they are all connected directly to the Collector of those (3) FGPF4633s, which in turn are connected directly to the pins going to the Zsub board.

Looking at the last picture I posted, all Gate to Collectors seemed to be shorting but I found it somewhat unlikely that all 3 are shorting. Seeing how these transistors would obviously have to be replaced, or the whole board replaced, I went ahead and snipped the Collector pin on the top side of the board of that left most 4633.. and whaddaya know... all 3 Coils stopped grounding, in turn, all 3 collectors of the 4633s stopped grounding.

Again, checked for shorts across the collectors to both Gate and Emitter for the remaining two good 4633s, still good. Just to take it a bit farther, I tested for shorts of the biasing signal at the gates just in case. Seeing the voltage divider between what looks like a 5ohm equivalency(two 10ohm in parallel) and a 10k ohm resistor (R224), i expected to see 10k ohms to ground.. and holy crap.. the 10K ohm resistor is done also, shorting out the biasing signal from the top right ICs!

(EDIT: Thinking about it, actually, i went ahead and clipped the whole 4633 that is blown, turns out that 10kohm resistor is fine.. it was shorting from Gate to Emitter..)

So I'm leaning more toward telling this person to just get a new zsus just because there could be some unexpected things come up. If it was my TV I would have no problem ordering replacement 4633s and reinstalling but since it's not, i'd feel more comfortable telling this person to get a new board...

whew!!! I feel good now. Time for a beer

[giotmucdden]

Re: LG 60PV450 - bad Zsus?

I have the same problem with my TV. I ordered new Zsus board but it still doesn't show video.can you show me how to turn on test pattern? I would like to test controller boards are working.
thanks

Hey guys.. looking for some input on this LG 60PV450 plasma

So, initial problem was there was no picture but sound could be heard. Popped it open and looked around for bad caps, didn't see any, they all looked pretty good. No problem there.

Tested all fuses for continuity, found that the fuse on the Zsus board was blown so I removed and inspected both sides of the board. Found also that out of the 3 huge copper inductors, one of the solder joints came loose along with some heat damage. Moreover, the other 2 inductors seemed to have cracked solder joints.
So I cleaned up the burnt solder joint and resoldered all the points to the inductors along with replacing the fuse with the same type (T6.3AH 250V).

Reinstalled the board and connections and turned it on. Still no picture but then came the click, click, click sounds from the relays. The TV would go right back to standby mode.

Disconnected the Zsus board connections, both from power supply and flexible cable from control board. Connected the test pattern jumper and removed the flexible cable from the main board to the control board. Turned it on and was able to get the test pattern to display.. of course it was a red and distorted tint as usually seen from a disconnected Zsus board.

Next, I removed test pattern generator jumper and reconnected the flexible cable from the main board to the control board. Turned it on and was able to get the regular picture display of channel, inputs, etc. (still no Zsus connected, red and blotchy display)

At this point I decided to test the voltages at various points on the Power supply and Ysus board.

Factory Voltage settings:
Va = 55V
Vs = 201V
-Vy = -178V
Vsc = 150V
Vzb = 110V

What I measured:
Va = 55V
Vs = 202V
-Vy = -178V
Vsc = 150V

Testing the Vzb is where my next problem is because once i reconnect everything on the Zsus board, it quickly goes back to the no picture, repeated clicking and standby mode. Holding my meter on the Vzb test point while turning it on also reads no voltage.
I'm almost certain the Zsus is bad but am not sure about the Zsub also.

I've been studying the past 2 days to try and give as much information as possible. I have a background in electronics but this is my first time delving into a plasma TV. Any more suggestions on test procedures, something I missed or a diagnosis would be much appreciated, Thanks!

~Dave