Grundig GUVLDHD3200

[tom66]

Re: Grundig GUVLDHD3200

a nice looking set now its up and running was it just the two items you replaced in the end? just the other two sets left to repair how are they doing?

Yeah, the fet and the SMD fuse. Also the main fuse but I had one lying around. The other stuff was fixing some crap solder joints. So it cost about 20p to fix.

The 50" pioneer will have some work done on it tonight, I'm going to see if it will be as simple as replacing the FET (I've got a mica pad now.)

The 42" will be fixed after some parts are ordered but I expect that to be easy to fix.

[vinceroger69]

Re: Grundig GUVLDHD3200

a nice looking set now its up and running was it just the two items you replaced in the end? just the other two sets left to repair how are they doing?

[tom66]

Re: Grundig GUVLDHD3200

Yep, it's fixed now.

Picture quality is pretty good for a cheap panel. AUO/Quanta Display did well.

One slight problem when I first plugged it in. BANG! Fuse blew & RCD went. Uh oh...

Well, it turned out someone had had a "go" at repairing the PSU (which was not the fault... as the backlight and sound worked fine.)

They had soldered a bare jumper wire from one cap to another (the caps were just loose in the board, not even properly soldered.) And this jumper wire was touching the frame (by chance, when I moved it, it must have touched.) It was on the primary side, and obviously this is a live-earth short, so it tripped the RCD and blew the fuse.

Fixed all the joints (several cold joints on the replaced components...) Also removed that stupid wire and soldered properly to the board. Nice working TV, fixed for next to nothing.

Also found the control connector from main board to PSU has a habit of coming slightly loose, this causes the backlight to go out but sound stays fine.

[budm]

Re: Grundig GUVLDHD3200

Check them blue caps by the transistor. Verify the value and the leakage resistance.
http://s807.photobucket.com/albums/y...Dell%20E193FP/
Sometime you can see it cracked or bulging on the side of the body:
http://s807.photobucket.com/albums/y...%20capacitors/

[momaka]

Re: Grundig GUVLDHD3200

@momaka, which Dell monitor you are working on

It's a Dell E193FPc, not sure who made it. Royer Oscilator indeed.
I'll create a new thread on in next week or so as not to go off topic in this thread.
Thanks for giving me a heads up on the problem.

[budm]

Re: Grundig GUVLDHD3200

@momaka, which Dell monitor you are working on, is the board made by BenQ, pictures? It may have bad tuning caps in the inverter output section since most old Dell/BenQ/HP use Royer Oscillator setup to drive the inverter transformers.

[tom66]

Re: Grundig GUVLDHD3200

Okay, board looks like it's fixed... will test tomorrow.

I was sceptical about the gate pin. However, I checked it and it does briefly start outputting a square wave for a few milliseconds before shutting down... I presume this is because the T-con IC isn't seeing a video signal and is awaiting one to power up Vgh (holding output off?) Board draws about 40mA at 5V idle (so nothing else is shorted, hooray!) and Vgh briefly pulses to ~5.5V before dropping out.

We shall see if it works.

[tom66]

Re: Grundig GUVLDHD3200

Yeah, I've fixed the board, but the TV is at my dad's place, so I will have to wait a few days before I can test it. It was quite difficult to get that MOSFET on as I lifted the gate pad for the FET while removing it (careless error) but luckily I think I've managed to fix it. We shall see...

[vinceroger69]

Re: Grundig GUVLDHD3200

anyjoy on repairing this set?

[tom66]

Re: Grundig GUVLDHD3200

All the big ceramics test good, and so does the diode. I'll check the other stuff later. I'm ordering a reel of 20 FETs and fuses so the worst case is I smoke another.

[momaka]

Re: Grundig GUVLDHD3200

Did you check for shorted ceramic caps yet? Is D300 good? Also check VGL and VGH for short to ground. If any of these have a fault, they can make your new MOSFET and fuse blow again.

I already had a similar experience this week with the inverter transistors for a 19" Dell LCD. They lasted exactly 1 second before becoming completely shorted. And I actually checked the circuit they were in quite a few times and didn't find anything. Very disappointing.

[tom66]

Got another Vestel 32" in to repair... cost £29.

Fault is: Backlight is on, but there is no picture (black screen.) I immediately suspected a T-con problem, as I'd had the same issue with another Vestel - an Acoustic Solutions.

All supply voltages are okay. TV turns on/off normally. I haven't tested sound.

As expected T-con fuse is blown, but that's not the only problem. A little SMD MOSFET has had a bad day... it's for the boost converter. Shorted in all directions.

This TV uses a Quanta Display LCD panel, which is quite an oldie! Quanta was bought out by AU Optronics in 2006. I am not sure how good it will be, I'm not expecting much.

I will update this thread when I get the replacement fuse and FET and I test the unit. The middle top pin is the DRAIN, the leftmost is GATE and the rightmost is SOURCE.