Sony PVM 2130QM - Dark picture, no colour on composite sources

[Retrorepair]

If you look at the attached, you can see the colour drive is just not strong enough.

Again, this is with sub brightness and picture controls turned to max and the screen volts turned up as far as they will go without displaying retrace lines. Yet all the voltages I've found so far look normal.

[Retrorepair]

And my composite video sources look like this. NTSC by the way looks the same and the front panel doesn't indicate it's found an NTSC signal.

The darker image there is with 75ohm termination enabled.

[Ambientnoise]

I’m not a tv person and this maybe obvious or daft but it looks like a low video gain problem. Have you checked/scoped the video signal path from the input connection ?

Good luck, frustrating issue !

Ken

[Retrorepair]

I think that may be my next task Ken, I know I have at least one iffy pin on the euro connector so could well be other issues lurking there. The Qb board does look fairly warped on one side.

[Retrorepair]

I'm pretty sure the connections throughout the Qa and Qb boards are ok so on to the next in line which brings me back to the B board. Someyhing funky going on there I think.

[Retrorepair]

I'm suspicious of the auto white balance IC (CXA1024S), does anyone happen to have a datasheet?

I also plan to completely bypass the Qa and Qb boards and add composite video directly to the B board input to see if that makes a difference.

It's times like this I really wish I still had a scope

[Retrorepair]

Bypassing the Qa and Qb boards yeilds the same black and white image so at least I think I can narrow it down to the B board now. I've also managed to tweak the screen pots enough that the image is bright enough to be servicable, even if it's still not quite as bright as I'd like so I'm going to put a pin in that issue for the moment.

I've checked voltages at IC302 and all look to be as one may expect looking at what the service manual recommends, I'm now a bit stuck where to go from here.

Does anyone have any idea that I can try without a scope?

[Retrorepair]

I think I may have stumbled across the solution to my dark image, even though I wasn't looking for it

Someone on the aussiearcade forum has a large thread on a similar model (2730) which started with him experiencing excessive colour bleed. It wound up being R702 on the neck which was reading almost short (comparatively). Someone else in the same thread also had an issue with several resistors on the neck board and had a very dark image (sound familiar?).

I took a look at my neck board and my R702 (in and out of circuit) reads 1m. It should be 680k and since this is connected directly to the screen pot, and I have the inverse issue to him, I think I'm on to a winner. R704 is also reading in the megs on my neck board (should be 470k) and R711 reads .8M initially before going back to it's appropriate 82k value so I think all 3 of these will be changed out including R705 which is a little lower than I think it should be.

I checked a parts Trinitron chassis I had which was of the same vintage and low and behold, the same resistors (all 1/2w solid carbon) read almost the same. I'm assuming this is a common issue by this point with these sets.

So I think (fingers crossed) that once I've replaced these resistors (I think I'll up the wattage to 1w, there's plenty of space for it) and the volume control IC on the amp board, my remaining problems will be the composite colour issue and the front panel controls doing nothing. I'd at the very least expect the brightness and sharpness to do something on my black and white image, or would these only affect chroma as opposed to the lonely luma?

Anyway, I'll post results once parts arrive, if anyone has suggestions for my composite colour issue in the mean time feel free!

The thread I mentioned by the way is here, it's 13 pages and full of useful info (maybe not all should be taken as gospel but results speak for themselves):
https://www.aussiearcade.com/topic/7...d-more/page/6/

[Retrorepair]

Sorry to post so much, but where should I be measuring B+? The manual says it should actually be 140v, I assume after R664 on Fa board?

It also says to adjust RV652 for the ref at pin 1 of IC651 to 32v+/-0.1v.. but the schematic says 3.2v at that pin. Typo?

[Retrorepair]

Replaced those resistors, did nothing I measured them again and they were fine, not idea what happened there, definitely tested them out of circuit the other day.

So I'm back to square one other than the volume control IC.

So first things first, I'll need to pull it apart again (becoming an expert at that) and adjust the B+ properly to 140v, I just need to make sure I'm measuring at the right point I suppose.

I may start looking at the neck board transistors next unless anyone has a better idea?

[Retrorepair]

Think this has turned into a log so I can keep track of what I've done with this thing.

So I adjusted the B+ to 140v measured off the 140v side of R664 and pin 1 of IC651 to 3.2v.

For now, I've replaced R1312 (220k) with an 82k and the picture looks perfect. This isn't right of course, but I can use the monitor while working out what's going on. Of course, this does nothing for the composite colour issue, but RGB looks great.

[Retrorepair]

So a little update to my tale of woe.

I replaced the volume control IC on the K board and still no sound.

Then i noticed the vol, treb, bass and bal inputs were reading next to nothing yet should be at 4.9v. This comes from B19 on the B board and is fed from IC103, a DA converter. This IC has voltages in all the right places, except the outputs.

Remember how I mentioned in passing the front panel buttons didn't seem to do anything for any input? This IC is what those button lead to before actually controlling the functions in other places. Things like brightness, colour, hue, volume, balance etc etc. The VCC, VDD, CLK, DAT, all inputs are exactly what they should be, outputs are all dead.

I now firmly believe this IC is dead and causing ALL my issues.

Will update here once I've replaced that.

[agardiner]

Fingers crossed!

[HurtyAC]

Sony Televisions from the 80's used these carbon rod resistors and they gave trouble during that time. These are carbon rod resistors and are used in high voltage circuits. If you use normal carbon on ceramic spiral cut resistors these are usually rated for a maximum voltage of 400V across them, yes resistors have a voltage rating! hence the use of carbon rod resistors. If you crush these when they have failed where the wires go into the body of the resistor it goes a bit green and fails. I use a 2 Watt resistor to replace these as carbon rod resistors are now hard to come by. When spiral cut carbon resistors have been fitted that cannot stand the voltage across them there will be burn around the circumference of the spiral cut because the voltage arced around this. This is why I was asking you for the tube voltages. Normally as the tube losses the high voltage G2 or similar the cathode drives goes low as they try to provide beam current but cannot. This does look like a dying tube but doesn't usually defocus. Had a work college diagnose a tube fault and he had ordered one which cost £2000 in 1992. Monitor was a BVM 2010P. I was on nights and saw the diagnosis. Got this on the bench yes the tube G2 was low, new resistor fitted and all then good again. He was reminded of his diagnosis now and again for a bit of fun. He was a good engineer so this can confuse the best of them. We did eventually use the ordered tube a number of years later. All engineers know measure the voltages FIRST!

[Maarten]

Originally Posted by Retrorepair

So a little update to my tale of woe.

I replaced the volume control IC on the K board and still no sound.

Then i noticed the vol, treb, bass and bal inputs were reading next to nothing yet should be at 4.9v. This comes from B19 on the B board and is fed from IC103, a DA converter. This IC has voltages in all the right places, except the outputs.

Remember how I mentioned in passing the front panel buttons didn't seem to do anything for any input? This IC is what those button lead to before actually controlling the functions in other places. Things like brightness, colour, hue, volume, balance etc etc. The VCC, VDD, CLK, DAT, all inputs are exactly what they should be, outputs are all dead.

Voltages in all the right places, so you have pulse trains on CLK and DAT when you try to change those settings?

[Retrorepair]

Originally Posted by Maarten

Voltages in all the right places, so you have pulse trains on CLK and DAT when you try to change those settings?

I've no way to know, no scope.

That does raise a good point though, if the colour is simply muted as a result of this IC failing, why doesn't the NTSC light on the front illuminate when fed an NTSC signal? I now wonder if something is interrupting the data bus or despite a voltage being present, maybe a missing clock?

I need a scope

[Retrorepair]

I do have a basic logic analyser though, that should work at that logic level

[Retrorepair]

Well the CLK and DAT lines into IC103 are definitely pulsing, I'm not sure if that's how it should look or not though. It seems to change when I press buttons on the front but again, no idea if the signal is correct. It seems a bit noisey but that could be my cheap analyser?

I'm going to replace and see what happens.

[Retrorepair]

So a little update, I replaced IC103 and I now have full front panel control, sound, brightness, it's ALMOST there, but composite sources are still black and white.

The saga continues I guess, but at least that's a stack of problems solved!

[agardiner]

Well done! And nice to know its coming back to life and the CRT was OK.