Fuzzy image after recapping deflection board on Sony BMV

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bounav
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Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

Hello,

I tried to recap the E board on my Sony BVM 20G1E and now the image is fuzzy.

See youtube illustrating the symptoms: https://youtu.be/6ah5zKHgoHA.

It's not lack of sync: External sync is turned on and as soon as it's enabled it does stabilises the image.

When I swap the E board with one from my other BVM (a 14G5E), the image is fine (all be it a smaller which is expected since it's the deflector board of a 14" tube). This confirms the issue is with the board I just recapped.

I checked the values and polarity of all the caps on the board, looked for bad solder joints and shorts, cleaned the back of the board with isopropanol...

Has anyone had that issue before?

I'm going to go look for the diagrams of that board in the service manual and try to see which part of the board could be to blame. Maybe something to do with the horizontal sync?
Last edited by bounav on Wed Jun 09, 2021 4:12 am, edited 1 time in total.
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NoAffinity
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by NoAffinity »

I know nothing about bvm's. But is there a flyback with a focus knob that can be adjusted?

:edit: search google for "bvm flyback adjustment". One if the results will be a link to a bvm manual on retrorgb. There is a section for focus adjustment, in the manual.

Sent from my SM-G955U using Tapatalk
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bounav
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

Thanks for your suggestion but I don't think it's a focus issue.

The image is sharp but it's "wiggling"/oscillating on the horizontal axis very fast.

Swapping the E board with another one give me a stable and sharp image, confirming the focus is fine?
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

Tonight I tried resetting the E board and other input boards to factory settings. It didn't make any difference (apart from messing up the picture's geometry ;) ).
Sefirosu789
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by Sefirosu789 »

Where did you get the caps/cap list from?

If its the same as the 20F1 series, I believe there are slight changes between some board revisions.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by NewSchoolBoxer »

That's extremely helpful you know which board is causing the fuzzy image, have a working board to compare to and that the image was better or different before you recapped.

I agree that the most obvious answer is you used the wrong cap list. Without studying the service manual too hard, seems BVM-14G1A/14G1E/14G1U share the same chassis: https://pro.sony/s3/cms-static-content/ ... 434151.pdf

That's the manual you used? I see E board diagrams are on 10-10 and 10-11. Electrical parts list starts on 9-1. Not saying you did this but you can't use a 22pF capacitor where it calls for a 10pF one. Must use equal or better tolerance and voltage limit and if it lists, say, ceramic, use ceramic capacitor and not tantalum if you can. The different types have different electrical properties.

That the horizontal but not vertical sync is messed up, I would guess a capacitor value or type is wrong so that the RC time constant is too high and it's not charging or discharging fast enough.

The other angle of attack is the 5-3 E board adjustments, assuming you have an oscilloscope. Confirm or adjust V Blank to 520 ±30 µsec, 16:9 H Blank to 11.5 ±0.3 µsec and 4:3 H Blank to 8.0 ±0.2 µsec. There tends to be more tolerance for horizontal sync than for vertical sync.

I never opened up my own PVM so I could be missing the problem entirely. Just wanted to think this through to help.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

Sefirosu789 wrote:Where did you get the caps/cap list from?

If its the same as the 20F1 series, I believe there are slight changes between some board revisions.
Hi,

Before recapping (only the electrolytic ones), i surveyed the board and wrote down all the references along with the values uF and voltage (as well as wether they are bipolar or electrolytic). Only then I compared with the list from the service manual and found no difference.

I learned the hard way never to take a part list from granted ;).

Also as part of my troubleshooting I checked the values of the boards I removed and did not find any unexpected values...
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

NewSchoolBoxer wrote:That's extremely helpful you know which board is causing the fuzzy image, have a working board to compare to and that the image was better or different before you recapped.

I agree that the most obvious answer is you used the wrong cap list. Without studying the service manual too hard, seems BVM-14G1A/14G1E/14G1U share the same chassis: https://pro.sony/s3/cms-static-content/ ... 434151.pdf

That's the manual you used? I see E board diagrams are on 10-10 and 10-11. Electrical parts list starts on 9-1. Not saying you did this but you can't use a 22pF capacitor where it calls for a 10pF one. Must use equal or better tolerance and voltage limit and if it lists, say, ceramic, use ceramic capacitor and not tantalum if you can. The different types have different electrical properties.

That the horizontal but not vertical sync is messed up, I would guess a capacitor value or type is wrong so that the RC time constant is too high and it's not charging or discharging fast enough.

The other angle of attack is the 5-3 E board adjustments, assuming you have an oscilloscope. Confirm or adjust V Blank to 520 ±30 µsec, 16:9 H Blank to 11.5 ±0.3 µsec and 4:3 H Blank to 8.0 ±0.2 µsec. There tends to be more tolerance for horizontal sync than for vertical sync.

I never opened up my own PVM so I could be missing the problem entirely. Just wanted to think this through to help.
Hi. Thanks. Yes that's the manual I've used yes.

I have only touched the electrolytic capacitors. But I agree with you somehow what I did messed up a time constraint...

I should be able to speak with savon pat this evening UK time. I'll see what he thinks and I might end up sending him the module if the extent of what needs to be done is beyond my skill set... I'm thinking adjustments like you mentioned.

And thanks for all the replies I got here! They were all very helpful ones.
Last edited by bounav on Thu Apr 08, 2021 8:34 pm, edited 1 time in total.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by NewSchoolBoxer »

Sorry, I posted link to a different manual. This is the one I was referencing: http://s3.amazonaws.com/retrorgb/assets ... Manual.pdf

You are the most prepared person to come here asking for help. Wrote down the references and compared to service manual list. I knew you got the polarity right since the capacitors explode if you don't. 8)

Then I'd check the capacitor tolerances since some in the manual have to be 5% and a 20% one could be off enough to de-sync. At least it's possible the sync calibration can compensate. Consider investing in an ESR meter. I don't have one but capacitors near end of lifespan can show correct C but have R that is too high. In a simple circuit, the time constant really is the R and C values multiplied together.

edit: I'm a fan of this video, minus all the ads, of an ESR meter in action on PCB board: https://www.youtube.com/watch?v=72sJ5Infuu0
The part about being able to replace with a higher farad capacitor, that's a general case. I think 330uF vs 220uF on RGB cable is fine but not on an active filter. Fixed RC explanation.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

NewSchoolBoxer wrote:Sorry, I posted link to a different manual. This is the one I was referencing: http://s3.amazonaws.com/retrorgb/assets ... Manual.pdf

You are the most prepared person to come here asking for help. Wrote down the references and compared to service manual list. I knew you got the polarity right since the capacitors explode if you don't. 8)

Then I'd check the capacitor tolerances since some in the manual have to be 5% and a 20% one could be off enough to de-sync. At least it's possible the sync calibration can compensate. Consider investing in an ESR meter. I don't have one but capacitors near end of lifespan can show correct C but have R that is too high. In a simple circuit, the time constant really is the R and C values multiplied together.

edit: I'm a fan of this video, minus all the ads, of an ESR meter in action on PCB board: https://www.youtube.com/watch?v=72sJ5Infuu0
The part about being able to replace with a higher farad capacitor, that's a general case. I think 330uF vs 220uF on RGB cable is fine but not on an active filter. Fixed RC explanation.
Thanks, well I'm very appreciative of the free help the community provides and I'd feel bad wasting your time! ;).

Thanks for the link to EEVblog. Great video in particual I had not seen that one. It's a great youtube channel.

I spoke to BVM service celebrity savonpat on Saturday and an he agreed that I should get an ESR meter to check the caps inline.
I'm waiting for an ESR meter one to arrive through the mail (I went for a GME DCR & ESR meter Model 236...).

I hope one of the new caps happens to be bad with a high ESR that would indeed explain the oscillation... I'll update this post to keep you posted.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by Fudoh »

I'm a fan of this video, minus all the ads, of an ESR meter in action on PCB board: https://www.youtube.com/watch?v=72sJ5Infuu0
indeed, thanks a lot for that. Didn't know this was a thing. Seems extremely useful, especially since it allows to go through a lot of caps without spending a lot of time and it doesn't require visual verification of bloating or similar symptoms.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

Time for an update.

I checked the caps with an ESR meter, replaced a few suspicious ones. But no luck.

Oddly, I found out that when the BVM's OSD menu is on; if I then I turn off the RGBS source (i.e. either the SNES or Megradrive I have connected to the BVM's input) the image is not longer fuzzy / oscillating on the horizontal axis.

Really weird isn't it?
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

Time for an update. I shipped my "E" and "ISR" boards from the UK to California, and once in the hands of Savonpat he was able to diagnose the problem really quickly:
An IC was defective on the E board. According to him it's a common fault. He replaced the part and added a heatsink on it.
He also tested the ISR board and found nothing wrong with it.
Now I'm hoping it won't take too long for the parts to come back.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by Bratwurst »

It would be helpful to post the exact part number of the IC for future reference in case anyone else encounters this issue.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

Bratwurst wrote:It would be helpful to post the exact part number of the IC for future reference in case anyone else encounters this issue.
I will when I get the board back.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

Just got the boards back.

Savon pat replaced Q061 on the E board. It's labeled "Horizontal Size Regulation Switching" in the service manual. He also fitted the component with a small heatsink so it should help.
Q061 8-729-015-28 TRANSISTOR IRFI9630GS
Hope this thread helps someone one day! Thanks all for your replies.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

Bad news, I found the time to test the hardware again and no luck: I stil get a "wobbly" image.

This time I tested with a PAL composite signal (instead of RGB+Sync) coming from a DVD player connected to one of the analogue inputs of a 21D board in slot 2 of the BVM.

When the BVM is on and the dvd player off, if I bring the OSD menu of the BVM the image is perfect.

Image

As soon as I turn on the dvd player, the image gets wobbly.

Image

I tested the transistor replacement in circuit (Q061) with my multi meter in "diode tester" mode and it checks out OK.
The old transistor that has been replaced by savonpat does test bad...
So savonpat _did_ fix an issue with the board... but but not the "wobblyness".

This is driving me insane.
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by bounav »

Armed with a print of page 201 of the service manual (detailing the schematics of the E board), I started poking around with my meter in continuity mode.
Then I put 1 and 1 together: having introduced the issue by recapping the whole board and the issue being related to horizontal sync, let's see if there are any issues between ICs and caps. Bingo, I found that I had broken trace between C022 and pin 46 of IC001.
Pin 46 of that chip being labelled "AFCFIL3" I assumed I was onto something.

Adding a bodge wire between pin 46 of IC001 and the + side of C022 fixed the issue!

Thanks so much everybody for contributing to this thread.

Hope this helps someone one day.

I think from now on I'll think twice before recapping all the caps... and now that I have an ESR meter that does in circuit testing it will certainly help!
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Re: Fuzzy image after recapping deflection board on Sony BMV

Post by BigBoss1964 »

bounav wrote:Armed with a print of page 201 of the service manual (detailing the schematics of the E board), I started poking around with my meter in continuity mode.
Then I put 1 and 1 together: having introduced the issue by recapping the whole board and the issue being related to horizontal sync, let's see if there are any issues between ICs and caps. Bingo, I found that I had broken trace between C022 and pin 46 of IC001.
Pin 46 of that chip being labelled "AFCFIL3" I assumed I was onto something.

Adding a bodge wire between pin 46 of IC001 and the + side of C022 fixed the issue!

Thanks so much everybody for contributing to this thread.

Hope this helps someone one day.

I think from now on I'll think twice before recapping all the caps... and now that I have an ESR meter that does in circuit testing it will certainly help!
Very helpful post bounav. I hope things are still working for you. I may not have so much recapping skills and time to do it but just wondring if the deflector board (E and D boards) for a BVM-20F1 [A-1346-356-B] would also fit and work on a 14F1. Would it be a
A. like-to-like replacement and nothing else needed,
B. yes would work but I need to tweak its pots etc for it to fit the geomtery of the 14-inch screen,
C: wouldn't work at all?
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