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Old 21st Oct 2017, 5:49 pm   #1
RetroHQ
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Default Sony BVM 2010P Troubleshooting

I've been troubleshooting a Sony BVM 2010P and could do with some help! Initially it wouldn't power on and I traced the issue to a dead diode in the PSU which was causing the the -150v rail to be faulty. Replacing the diode (I replaced both positive and negative 150v rail diodes for completeness) it powers up, but I get a mess on the screen (https://m.youtube.com/watch?v=P7NyeYWxXNA). I also recapped the PSU board.

I've since found the RGB signals, at least for the crosshatch test pattern, get as far as the input to the video amplifier BK board. Fiddling with brightness and contrast I can see the signals (on my scope) for the RGB input change as you'd expect with amplitude changes. There are two inputs to the BK board for blanking and some kind of calibration pulse which both look sensible, but the signal is not being amplified. One of the test points should result in a 3.6v pp signal, and I'm getting more like 340mv there, the same for all RGB channels. The resulting signal is basically flat, biased down to about -130v.

Now, I know the BI board is coupled with the BK board with drive and bias signals. So at this point I don't know where to go next. It could be an issue with a common component on the BK board, or something to do with the BI board giving bad bias and drive signals. If anyone can help troubleshoot this further I would really appreciate it! I'd love to get this old beast working.
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Old 21st Oct 2017, 9:31 pm   #2
John123
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Default Re: Sony BVM 2010P Troubleshooting

Hi, I'm no expert on these, but the lack of a full-height raster and general unresponsiveness (by the looks of things), makes me wonder if you still have a power supply issue.

Go back to basics and double-check all of your power supply rails just to make sure everything's present and correct (under load). Seeing as your initial fault was in the PSU, it remains highly suspect and would need going over with a fine-toothed comb.

Presumably recapping has taken care of any possible noise/ ripple issues, but as these are quite complex beasts it's always a good idea to go back and scrutinise any work you've already done.

Also I know it may be obvious, but make sure replaced components are up to spec (if using equivalents), and are sourced from reputable outlets. Check service information for the location of fuses/ IC protectors and double-check. Anything marked '!' will be safety critical, and should not be substituted.
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Old 22nd Oct 2017, 10:58 am   #3
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Default Re: Sony BVM 2010P Troubleshooting

Everything looked ok, as I remember, but I will go back a double check all the voltage rails from the PSU. The monitor appears to be largely working (ie. being able to produce the cross-hatch signal and sync, which I can clearly see on a scope), but the final RGB amp section is not functioning.

It could possibly still be a PSU issue, but my feeling is that when the -150v rail went down, it took something with it...
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Old 22nd Oct 2017, 11:20 am   #4
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Default Re: Sony BVM 2010P Troubleshooting

Hi Can you take a picture of the BK board sat in the top of the monitor. There are some 10uF 200 volt caps that couple clamping pulses to the video drive stage and if these do not work the the video amps will not bias themselves. You can get the same if the tube grid 2 bias is wrong. Don't forget the earth on your RGB input and the set will only be 625 line.The RGB input will also need the separate sync input too. Photo the front pane when it is open and on so I can see what settings you have done. Know these monitors very well and should be able to get this going. They are very complex. There are some 10uf caps that fail on the frame output board also but we will deal with this later. The sync separator has 17 transistors in it! Do you know if you have the composite PAL input board fitted?

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Old 22nd Oct 2017, 1:51 pm   #5
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Default Re: Sony BVM 2010P Troubleshooting

Awesome, very pleased to hear from you Hurty. Pictures attached of BK board and panel settings.

I found changing the controls on the front and top of the control panel made very little difference at all to the picture. I could get the "image" to fill the monitor with one change, but virtually everything else had no real noticeable effect.

However, I can confirm that the settings make a difference when viewing the RGB signals at the input to the video amp. I can see the crosshatch when enabled, I can see the amplitude of the signal change with brightness / contrast and I can see the signal being enabled / disabled with the RGB buttons on the front. So a lot of it is working.

Also, the AFC pulse you mention, that is present with 12vpp at the input to the BK board and I checked this at the point you mention (I think) by the AC coupling cap and it was inverted (I think), still 12vpp but biased down to -130v.

Any further help on what to test would be much appreciated!
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Old 22nd Oct 2017, 4:37 pm   #6
HurtyAC
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Default Re: Sony BVM 2010P Troubleshooting

Hi The BK board has the black electrolytics (about 4 in each channel) and I'm trying to remember the ones that fail are 2.2 or 10uF, best tested by soldering a capacitor across them. I will have to see if I still have the circuit diagram for the board and will get back to you. I think you said that video was arriving to the BK board. It is a complex circuit which fully biases itself. I have had much fun with these over the years. They cost over £5,500 when new in 1989 plus options. The last tube I bought for one in about 1996 was over £2000 capable of 900 lines (horizontal) of resolution.
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Old 22nd Oct 2017, 7:36 pm   #7
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Default Re: Sony BVM 2010P Troubleshooting

Yes, everything arriving at the BK board looks right to me (apart from drive and bias, as I have no idea what they should be!). For a few milliseconds at startup, the output from the amp looks correct, but as the output gradually drifts towards -130v (I say gradually, its just a second or so) then the output just becomes flat. So it does sort of work.... to a degree.

The service manual is here: http://www.retrorgb.com/files/monito...ice_Manual.pdf

I've poured over the BK and PSU schematics a lot, but I'm afraid I'm not that great at tracing these things through and figuring out what should be happening! I can manage digital electronics pretty well (my background is really a software engineer, I've just turned to hardware in the last few years), but this is way out of my comfort zone!

The common part of the circuit to all channels is the pulse detect going into the clamp pulse buffer and the blanking going into the blank pulse buffer. The blanking looks good, as does the AFC pulse coming in. I thought the AFC pulse looked OK going into the clamp pulse buffer, but I could be wrong! Given this part is common to all channels, I had suspected this could be the problem.
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Old 23rd Oct 2017, 11:13 pm   #8
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Default Re: Sony BVM 2010P Troubleshooting

Definitely replace the 10UF 160 capacitors, if they are still the original ones, they will be high ESR or completely open.
I have seen them leak as well, causing a burnt track under the capacitor, and this may have contributed to your original PSU failure.

In fact, given the age of these monitors (which first came in 1987), its worth checking/replacing capacitors on some of the other cards, especially the two scan boards (EA & EB) as well as the EHT board (PA).

The tubes on these monitors really do last !
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Old 24th Oct 2017, 9:19 am   #9
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Default Re: Sony BVM 2010P Troubleshooting

I'd go further and say change all the electrolytics on the board. I spent quite a few years fixing Sony broadcast monitors (including this model) and the collective thoughts of the maintenance workshop were that they were hideously complex - which resulted in excellent pictures - but a nightmare to fix when they went wrong.

I remember this model (and it's very similar cousins) for three faults. Firstly a failure to go into 'auto white balance' mode when using the screen probe which was a failure of two particular 8 pin 74 series logic SM chips (can't remember which board now I'm afraid after all these years). This was the only semiconductor fault we used to have on this model.

Secondly, all other faults were always related to high ESR capacitors. So, definitely change them all on the board without thinking about it and see how you get on.

Thirdly, all the models using the same CRT had a tendency to eventually suffer from blue flashing, I think it was flashing over internally. Hope you're lucky with that one, fingers crossed for you.
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Old 24th Oct 2017, 9:25 am   #10
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Default Re: Sony BVM 2010P Troubleshooting

Thank-you both, I'll do a recap on the BK board next then. Initially I didn't really consider this partly because of the original fault given by the previous owner of "worked perfectly until it was moved, now it wont power on" and also because each channel seems to be failing in the same way. Its not to say there is a cap issue causing a common fault though, of-course.

I will report back.
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Old 24th Oct 2017, 4:58 pm   #11
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Default Re: Sony BVM 2010P Troubleshooting

Would something like this be suitable for the 10uf 160v cap replacement?

http://uk.farnell.com/panasonic-elec...rad/dp/9693181

There are so many different electrolytic caps I have no idea really of their characteristics.
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Old 24th Oct 2017, 5:24 pm   #12
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Default Re: Sony BVM 2010P Troubleshooting

I don’t see why not. When we were repairing Sony monitors in the workshop we just reached out to the component drawers and took out standard electrolytic caps - but always ensuring it was 105degrees working as the internals of Sony monitors were always pretty densely packed with electronics = heat.
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Old 24th Oct 2017, 6:01 pm   #13
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Default Re: Sony BVM 2010P Troubleshooting

Many thanks.

A bit more random fun -- I noticed 3 caps soldered on the underside of the board across the variable caps on the BK board. The adhesive pads had become brittle and seemed to have caused corrosion to the surrounding solder joints around all the pads. Cleaned up and fluxed / reflowed the corroded joint, but no change in behavior.

It was interesting as I saw recently (on YouTube) a Commodore 1084 monitor with colour issues which ended up being some gunk on the PCB which had become conductive over time and arcing had basically eaten through a local diode causing the odd intermittent behavior. The weird things that happen when you leave something for 30 years...
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Old 24th Oct 2017, 7:04 pm   #14
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Default Re: Sony BVM 2010P Troubleshooting

Indeed that old circuit glue is becoming somewhat notorious as time goes on. If you come across any of that dark brown/ mustard coloured gunk, best to be gone with it ASAP. Prevention is better than cure, as they say..
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Old 24th Oct 2017, 9:01 pm   #15
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Default Re: Sony BVM 2010P Troubleshooting

That horrible glue that Sony loved so much is best removed on sight! I've had a Sony TV camera which was encrusted with the stuff, kept having random colour issues, cleaned off the glue and resoldered everything that had been affected and all was well again. Also had a Sony FH-15r stereo that had this stuff plastered round some caps in the amplifier, it had gone hard and brown, some of it was on other components and it had caused green corrosion on the legs. I had to replace some of them as the solder wouldn't take to the legs after that. It also damages PCB tracks too.

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Old 10th Dec 2017, 3:16 pm   #16
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Default Re: Sony BVM 2010P Troubleshooting

Just wondering if you managed to recap the BK board and whether this resolved your issue ?
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