Dead screen, no pilot light

[burntfingers]

This set has the normal 12 and 24 volts going [see picture], but there is no standby light on.
[A privately imported set with no backup of any kind on the Internet or manufacture, it appears. Model is DigitalArt DA-32TW04, anyway.]
There is life in the signals board with some hot ICs.
It looks like this board could be faulty.
What do you think?

[tom66]

Re: Dead screen, no pilot light

If I'm not mistaken that's a Vestel set. They are made in Turkey.

Vestel TVs are some of the worst to service. The ugly, nearly impossible to follow wiring, poorly laid out main board, intermittent faults (especially caps that don't bulge and bad solder joints) and the difficulty of finding service manuals are just some of the reasons.

Vestel power supplies usually output 3.3V standby, 5V standby, 5V run, 12V and 24V. Check all are present. Check for ~395V across main bulk cap when running (should be 320V in standby.)

Note these sets sometimes turn OFF the standby indicator when running so check the backlights aren't faulty. And do you get sound?

[burntfingers]

Re: Dead screen, no pilot light

No sound that I can hear, since I have no means of getting any station or select AV.
Lamps are also dead, and don't turn on ever.
There is power feeding the lamps cable, though, but I don't see the inverters - must be under the metal frame.
Indeed, the soldering looks unprofessional - poor quality.
The other set with the vertical line is from the same company.

[tom66]

Re: Dead screen, no pilot light

No sound that I can hear, since I have no means of getting any station or select AV.
Lamps are also dead, and don't turn on ever.
There is power feeding the lamps cable, though, but I don't see the inverters - must be under the metal frame.
Indeed, the soldering looks unprofessional - poor quality.
The other set with the vertical line is from the same company.

Check for other rails on PSU. If not present, it's not worth debugging, just get a new PSU. You will spend hours chasing around faults. These supplies seem to work by the will of a deity - but the slightest thing wrong and they go completely belly-up.

[burntfingers]

Re: Dead screen, no pilot light

Yes, thank you.
I already sent email to Li Shin Enterprise [in CHina or Taiwan] for diagram of PSU - not sure if I'm lucky - PS model n. 0420D02216].
Funny that the only panel with the logo Vestel is the small sound one. All other boards have no clear logo.
It indeed looks a bad set.

[momaka]

Re: Dead screen, no pilot light

The board next to the PSU seems to have regulators and whatnot on it. Post some close-up shots of that board so we can identify what they are. Also post a few pictures of the PSU. Looks like a single, always-on power supply (i.e. no standby circuit) with PFC, but I can't confirm that without good pictures. It could be that this power supply only provides 12v nad 24v and the rest of the voltages are derived from that other board next to the power supply (so the PSU may actually be working fine).

[burntfingers]

Re: Dead screen, no pilot light

The board next to the PSU seems to have regulators and whatnot on it. Post some close-up shots of that board so we can identify what they are. Also post a few pictures of the PSU. Looks like a single, always-on power supply (i.e. no standby circuit) with PFC, but I can't confirm that without good pictures. It could be that this power supply only provides 12v nad 24v and the rest of the voltages are derived from that other board next to the power supply (so the PSU may actually be working fine).

Yes, the regulators work fine - voltages as per photo - although the 23.6 for inverters is not switched on sometimes - I need to turn the on/off switch two or three times; the green LED comes on all the time.

There is also 5 volts on the standby LED, but it does not turn on.
HS plate is rather hot after a while.
In other words, all voltages seem to be OK, but the set remains dormant.

[tom66]

Re: Dead screen, no pilot light

Check the 5V standby.

If intermittent or low, replace the 78L05 on the PSU.

[burntfingers]

Re: Dead screen, no pilot light

5v is OK, as the 3.3v too.
Power supply seems to hum normally.
I noticed that the supply to the control buttons is only 2.6 - not sure if that is OK.
Nothing happens, even if I remove the supply to inverters.
I still suspect the signals board is faulty.

[tom66]

Re: Dead screen, no pilot light

What is the part code on the motherboard? (Usually 17MBxx-x, where x is any digit.)

[burntfingers]

Re: Dead screen, no pilot light

What is the part code on the motherboard? (Usually 17MBxx-x, where x is any digit.)

Code number on that motherboard is 17MB11-2, VESTEL

[tom66]

Re: Dead screen, no pilot light

Okay, service manuals:

http://www.eserviceinfo.com/download...el_17mb11.html or
http://www.eserviceinfo.com/download...%22%20TFT.html

Check the pins 1 and 6 of PL602. Pin 1 should be >1.5V and pin 2 should be <0.2V if I recall correctly.

Check regulator IC600. Output should be about 8V. Diode is wrong way around in schematic, but check if it is short circuit.

[burntfingers]

Re: Dead screen, no pilot light

Okay, service manuals:

http://www.eserviceinfo.com/download...el_17mb11.html or
http://www.eserviceinfo.com/download...%22%20TFT.html

Check the pins 1 and 6 of PL602. Pin 1 should be >1.5V and pin 2 should be <0.2V if I recall correctly.

Check regulator IC600. Output should be about 8V. Diode is wrong way around in schematic, but check if it is short circuit.

Thanks very much for your kind help.
Downloaded the diagrams, thanks.
I will check a few points tomorrow.
So far, I've checked regulator IC600 - looks OK, in 12volts out 7volts.
Plug PL602 is not part of this board, it appears, but I'll check better tomorrow.
Quite tired now, after a busy day [and also looking after my granddaughter ].
Goodnight.

[burntfingers]

Re: Dead screen, no pilot light

Well, found Plug 602 which goes to plug 104 on the PS interface board.
Pin 1 is dead, no voltage present on both ends of the cable, and also checked under the interface board.
Pin 6 reads .017 volts.
I could not locate in the diagram any source for that pin 1 voltage, like I did not find the 8 volt supply mentioned in the PS description of the manual.
All other voltages are present and accurate, and green LED is happily on, the set being absolutely dormant!
I also measured the caps in circuit and look fine.

[tom66]

Re: Dead screen, no pilot light

And you are still getting 24V out?

What is the voltage across the big 150u/450V cap on the power supply (if you can get to it)?

I would suspect a main board problem.

[selldoor]

Re: Dead screen, no pilot light

Whilst it is probably the least of your problems you say "There is also 5 volts on the standby LED, but it does not turn on." could it be that the led is just burnt out?
Can you try another led or try and light it with external power?


ALSO

Also you say"I have no means of getting any station or select AV." what do you mean? I can understand no stations but have you anything you can set up - a dvd player or vcr that you know is working and can attach by scart or composite cables then even without seeing the screen . Set it going then cycle through the function buttton or remote (if you have one) to see if you can hear the sound of the dvd or tape?

[burntfingers]

Re: Dead screen, no pilot light

Went to measure it.
400 volts - but strange, it read 300 a few times.
I removed the cap which measure 137, connected a bigger one - 180nF - but no good results.
Now with the top HS out, I can hear some crackling going on inside some transformer.
I have to investigate why.
Meantime, the 24 volts supply is fine.
I had noticed yesterday that when switched on, sometimes the 24 is not present.
I have to switch off and on again to get that voltage.
I'm going to check caps on that board.

[burntfingers]

Re: Dead screen, no pilot light

Whilst it is probably the least of your problems you say "There is also 5 volts on the standby LED, but it does not turn on." could it be that the led is just burnt out?
Can you try another led or try and light it with external power?

I will do that.
But a burnt standby LED would not cause the complete shut down of the lamps and screen, would it?

[selldoor]

Re: Dead screen, no pilot light

"But a burnt standby LED would not cause the complete shut down of the lamps and screen, would it?"

I dont think so - as I said its probably the least of your problems but one less thing to
have to think about. See also I have added a bit about setting up AV in that post

[tom66]

Re: Dead screen, no pilot light

I didn't notice this board is using an add-on DC-DC converter. Check the output voltages on this converter, across the main caps. They should be 5V and 3.3V. Were these the voltages you were reporting when I asked you to check 5V and 3.3V?

Those Lelon caps could be bad, too, but I think that would cause a low supply voltage, which would be obvious. Also, Lelon seem to think copying Panasonic's T-vent is fun, they can't seem to make up their mind about whether to use an X or a three-way star.