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Old 16th Jun 2022, 2:05 pm   #41
Maarten
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Makes sense. If you have any kind of consistent pulse train, chances were the IC was indeed defective, as you demonstrated by replacing it.
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Old 16th Jun 2022, 3:12 pm   #42
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

I've a feeling I may need a scope to diagnose the remaining lack of chroma though. Even if I have voltage where it should be, the signal itself is critical. I'll take a look later but I'm keeping an eye out for a cheap scope.
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Old 16th Jun 2022, 11:28 pm   #43
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

I wonder if the IC was harmed by static or even a flashover? Might be worth running it with the cover off in a dim room to see if there's any evidence.
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Old 17th Jun 2022, 8:03 am   #44
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

I've been running it for several hours with the case off it a fairly dim room and not noticed anything like that. I've not seen an issue like this anywhere else online either.

I've also not seen this odd chroma loss reported anywhere else with this model. I can't find any missing or incorrect voltages according to the manual on the B board and I don't know where else the problem could be.

Unless anyone has any ideas, I'm going to have to get myself a scope and investigate further. This PVM was intended for VHS use too and while I'm happy to have got the other issues fixed, this one is the biggest issue for me
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Old 17th Jun 2022, 8:23 am   #45
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

It just seems odd that one or more ICs would fail, and was wondering if there was a common cause.
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Old 17th Jun 2022, 12:03 pm   #46
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

It does. It could have been a bad batch, or could have just been well used. I can't help but think it's somehow related to the lack of chroma, but other than maybe the VCC, I don't know what else would connect the two circuits?
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Old 19th Jun 2022, 1:44 pm   #47
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Actually, they do have something in common, Q301. Thisnis the colour clamp transistor. Maybe I should look at that next.
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Old 29th Jun 2022, 2:19 am   #48
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

The only thing I've found odd was pin 8 of IC 301 being at 0v while it should be 5v or there abouts. Possibly the transistor (Q358 connected by the collector) it is at fault? The manual seems to indicate there's no condition where it should be at 0v so maybe?

The IC is a CXA1001AP for which I can't find a datasheet or pinout anywhere. The pin on the schematic is labeled "COL" but that means not a lot to me. Is it an input or an output? I assume an input? What's the function of this pin exactly? Who knows.

For the record, unsurprisingly, S-Video is black and white also.

Last edited by Retrorepair; 29th Jun 2022 at 2:40 am.
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Old 29th Jun 2022, 2:34 am   #49
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Attached are my suspect components, any ideas on which I should be looking at for my lack of 5v or there abouts?
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Old 29th Jun 2022, 2:39 am   #50
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Maybe these too? It seems a huge coincidence the suspicious signal and it's supporting components are in close contact with the IC that failed. Especially considering the label on IC301 and IC103.
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Old 29th Jun 2022, 8:14 am   #51
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Any help?

http://antennafundamental.blogspot.c...01-ap.html?m=1

The "SHP" input pin 32, stands for "Sharpness", occasionally referred to as "colour transient improvement" – it is an active filter circuit within the luminance path that applies a variable h.f. boost to the luminance signal, usually just before the RGB output amplifier stages in the IC!

These i.c.s are very critical with regard to their pulse drive inputs from the timebases and the associated d.c. levels on these waveforms, so you do need to look at pins 38 and 39 with an oscilloscope (very carefully, when you get one!) as oddities here will cause all sorts of baffling symptoms – frame TB amplifier i.c.s can fail in a way that affects the blanking/sandcastle pulse to the jungle i.c. without causing an obvious field scan defect, and the frame TB amplifier IC flyback boost capacitor (usually about 47–100μ, 35 V or 50 V) can also dry up causing weird picture or colour problems because the shape and d.c. level of the blanking pulse is affected!

Also beware of leaky ceramic disc capacitors on integrated circuit pins!

I can probably draught a block diagram of the CXA1001P for you but there's no data to be found anywhere that I can see!

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Old 29th Jun 2022, 12:34 pm   #52
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Further to my above note, Have you checked the G2 setting according to the manual?

I'm fairly certain that the CXA1001P incorporates "auto grey scale correction" – this operates by sending a special series of negative test–pulses to the cathodes of the CRT during the field blanking interval and measuring the cathode current, adjusting the d.c. pedestal on the RGB outputs after each until each gun tracks equally, large and incorrect setting of the G2 control will affect the correct operation of this circuit, as will unfortunately, too low an emission tube!

https://worldradiohistory.com/UK/Pra...on-1994-03.pdf

See pages 53 & 54 of the PDF I've linked above!

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Old 29th Jun 2022, 6:56 pm   #53
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Some interesting points Chris, yes I've adjusted the G2 and it's pretty much spot on. I do wonder, does the auto grayscale compensation affect RGB? Because that's absolutely perfect, it just appears to be chroma that's absent.

I'm tempted to give up and use an external RF/composite decoder. Annoying really as I had a couple at my old place and binned them as no one wanted them!

I do want to fix this I just don't know what time/money I can afford to put into it, it's been quite the project so far. I'd love a scope but I'd likely only use it for this.

Anyone know of any techs in North Wales?
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Old 30th Jun 2022, 7:50 am   #54
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

What about Glyn? Forum member - Welsh Anorak
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Old 30th Jun 2022, 11:00 am   #55
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Good shout, he's about an hour from me, I'll give him a call
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Old 2nd Jul 2022, 8:54 am   #56
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Hi,
Regarding the lack of colour in composite mode, did you check the Xtal of the colour decoder (assuming it's an analog colour decoder) ?
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Old 15th Jul 2022, 6:41 pm   #57
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Quote:
Originally Posted by marceljack View Post
Hi,
Regarding the lack of colour in composite mode, did you check the Xtal of the colour decoder (assuming it's an analog colour decoder) ?
I did change the pal and ntsc xtals (which likely has made matters worse) but didn't think about the xtal for the IC itself. I'd imagine if that was duff more would be wrong?

Does anyone know if Glyn is active by the way? I can't seem to get hold of him.
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Old 16th Jul 2022, 3:33 pm   #58
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Default Re: Sony PVM 2130QM - Dark picture, no colour on composite sources

Sorry - I am active but this isn't a chassis I've had any experience of so I'm afraid I'd be in the dark myself. Not sure how much use I'd be to you I'm afraid.
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