No Menu, nothing!

[burntfingers]

LG RT-29FB50VE

This set has raster - blue screen, but NOTHING ELSE!
No stations, no sound, no nothing.
I also have no diagram!!... lol

Microprocessor supply, I wonder?
5V is present.
Chip gone?

[burntfingers]

Re: No Menu, nothing!

Blue screen only visible after grid control up - with flyback.

Injected video at video in, but nothing.

[dumpystig]

Re: No Menu, nothing!

I always reckon it's a good idea to brush/vacuum the accumulated dust and crap if present - makes things easier as I go along inspecting components etc.. Looks like your board could do with a clean

[burntfingers]

Re: No Menu, nothing!

I always reckon it's a good idea to brush/vacuum the accumulated dust and crap if present - makes things easier as I go along inspecting components etc.. Looks like your board could do with a clean

True.
I do clean the sets, and this one surely needs it!

[burntfingers]

Re: No Menu, nothing!

Wrong diagnostic, folks, sorry!

After handling plugs on the main board, I now get stations and sound, very pale picture with no contrast at all - I went looking for bad joints around plugs, too, but found none.
I asked the customer to get me the remote control to see if I can increase the contrast.
Pressing local Menu I see a very faint square on the screen but nothing visible enough to distinguish information.
I checked the Colour chip's temperature on the CRT base PCB and it was warm.

[Village Electronics]

Re: No Menu, nothing!

Wrong diagnostic, folks, sorry!

After handling plugs on the main board, I now get stations and sound, very pale picture with no contrast at all - I went looking for bad joints around plugs, too, but found none.
I asked the customer to get me the remote control to see if I can increase the contrast.
Pressing local Menu I see a very faint square on the screen but nothing visible enough to distinguish information.
I checked the Colour chip's temperature on the CRT base PCB and it was warm.

Check the 200 Volt supply to the CRT.

[burntfingers]

Re: No Menu, nothing!

Check the 200 Volt supply to the CRT.

All supplies are there - 195 volts is present at pin 6 of IC TDA6109JF - board on the CRT socket.
The scope does not show colour waves at pins 42, 43, 44 of processor VCT3804BD6.
I'm confused.
Do I need the remote control to bring up levels or not?
[Customer left the RC at home, the usual misdemeanour...]
I see a very faint picture after increasing the grid control on the line transformer.
Sound is fine.

[Krankshaft]

Re: No Menu, nothing!

Very faint picture is the screen voltage from the flyback voltage divider within spec?

The color outputs from the VCT3804BD6 are pins 105 R, 106 G, and 107 B, respectively.

[burntfingers]

Re: No Menu, nothing!

Very faint picture is the screen voltage from the flyback voltage divider within spec?

Focus and screen voltage operate normally.
Flyback appears, too.
But the picture is without contrast and brightness.
Could it not be the settings were lowered to minimum with the RC?

I know the settings should reset to default at switching on, but you're never sure until you are sure!

[Krankshaft]

Re: No Menu, nothing!

The anode voltage is ok too right?

Most OSD user color settings are stored in an EEPROM with the channel availability info.

I've posted the pinouts for the color outputs from the datasheet see if you get a waveform there.

I wouldn't jump to any conclusions until you can get into the OSD and have a look.

[burntfingers]

Re: No Menu, nothing!

Focus and screen voltage operate normally.
Flyback appears, too.
But the picture is without contrast and brightness.
Could it not be the settings were lowered to minimum with the RC?

I know the settings should reset to default at switching on, but you're never sure until you are sure!

This is how the picture looks [with grid supply almost at the highest].

[burntfingers]

Re: No Menu, nothing!

Very faint picture is the screen voltage from the flyback voltage divider within spec?

The color outputs from the VCT3804BD6 are pins 105 R, 106 G, and 107 B, respectively.

That IC is a 64-pin one.
I did check outputs at pins 42, 43, 44 for the colour signals: no signals found.
4.9 volts at each.

[Village Electronics]

Re: No Menu, nothing!

That IC is a 64-pin one.
I did check outputs at pins 42, 43, 44 for the colour signals: no signals found.
4.9 volts at each.

Looks like the resistor between the 2 caps above the word Micronas may be burned through. The one next to the green coil.

[burntfingers]

Re: No Menu, nothing!

Looks like the resistor between the 2 caps above the word Micronas may be burned through. The one next to the green coil.

Checked that resistor - R24, next to C25; reads OK, 10K.

Tanya does not have this diagram, and I'm stuck!
I need to repair this particular set; client is one of those good ones, Always pays with no complaint.

[Village Electronics]

Re: No Menu, nothing!

Checked that resistor - R24, next to C25; reads OK, 10K.

Tanya does not have this diagram, and I'm stuck!
I need to repair this particular set; client is one of those good ones, Always pays with no complaint.

I see now that it is not burned at all. It must be something common to all 3 colors. Power supplies, chips, grounds, CRT.

There is a real good clue there. You have retrace lines. I bet you have a bad filter on the 200 volt line like I said before.
Go to the FBT. Look for the 200 volt diode and filter cap that supplies the CRT. They are usually like 1mfd to 10mfd@250 or so
if memory serves.

[PlainBill]

Re: No Menu, nothing!

Checked that resistor - R24, next to C25; reads OK, 10K.

Tanya does not have this diagram, and I'm stuck!
I need to repair this particular set; client is one of those good ones, Always pays with no complaint.

First, the picky thing. the site is 'Elektrotanya'. Calling it 'Tanya' doesn't help someone trying to follow your lead.

Next, in the glory days of CRT TVs, most manuals were filed under the chassis number, because the same chassis would be used in several models. This is chassis MC-022A. Searching for that will be more productive.

Also, an elementary step is to Google the model number and 'schematic'. This will result in many false hits for the sites selling service manuals, but also has a good chance of finding the service manual. Googling 29FB50VE schematic brought up this as the 6th hit.

This site has a number of useful utilities, including a model to chassis cross reference.

And FINALLY, putting meaningful information in the title of a thread helps. 'No Menu, nothing!' isn't meaningful. 'LG RT 29FB50VE' is.

PlainBill

[burntfingers]

Re: No Menu, nothing!

First, the picky thing. the site is 'Elektrotanya'. Calling it 'Tanya' doesn't help someone trying to follow your lead.

Next, in the glory days of CRT TVs, most manuals were filed under the chassis number, because the same chassis would be used in several models. This is chassis MC-022A. Searching for that will be more productive.

Also, an elementary step is to Google the model number and 'schematic'. This will result in many false hits for the sites selling service manuals, but also has a good chance of finding the service manual. Googling 29FB50VE schematic brought up this as the 6th hit.

This site has a number of useful utilities, including a model to chassis cross reference.

And FINALLY, putting meaningful information in the title of a thread helps. 'No Menu, nothing!' isn't meaningful. 'LG RT 29FB50VE' is.

PlainBill

Good advice PB, thanks.
ALSO, I think I'm misleading you guys, here.
The screen picture I posted is not reflecting the fault as when I got the set; it shows that blue with flyback lines screen only when I increase the grid control at the flyback transformer [lopt].
With the normal setting I would not see anything on the screen, only hear the station's sound.
I've removed solder from M/processor's pins 42, 43 and 44 to see if I got colour signal, but nothing showed; still 4.9volts present.

Customer brought RC, but doesn't help a thing.


Thanks very much for the link to the diagram, PB; much appreciated.
Tomorrow, I will use it to check supplies around the micro processor chip.
It now looks to me that the chip is the culprit.
My supplier does not stock it; I've checked it already.

[burntfingers]

Re: No Menu, nothing!

That IC is a 64-pin one.
I did check outputs at pins 42, 43, 44 for the colour signals: no signals found.
4.9 volts at each.

I removed solder from those three legs [RGB output] of m/processor
and measured the signal with the scope, but found no signal.
Would it be a sure indication that the IC is faulty?

[PlainBill]

Re: No Menu, nothing!

I removed solder from those three legs [RGB output] of m/processor
and measured the signal with the scope, but found no signal.
Would it be a sure indication that the IC is faulty?

A sure sign? No. But it does indicate the problem is not in Q505 - Q508. Now you should check voltages and signals into IC01.

PlainBill

[burntfingers]

Re: No Menu, nothing!

A sure sign? No. But it does indicate the problem is not in Q505 - Q508. Now you should check voltages and signals into IC01.

PlainBill

OK.
I've checked all the voltages around the IC, and they check right - also followed the troubleshooting steps in the diagram.

It seems to me now, more than before, that the IC is not processing colour outputs internally, therefore, faulty.
I've been trying to find one such IC from LG, but funny enough this particular model is not listed!