[SOLVED] Blast City's Nanao MS2930 Contrast issue after recapped HELP!!!!

[koki]

I just recapped Nanao MS2930 due to "black goop leakage" on the chasis. All capacitor I used is 85 degree specs.
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After recapped, cleaning and reassembly to the cab there was some issue.
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I tested with CPS2 and MVS when start the game (RAM check screen, capcom logo etc.) there is no problem.
Until the title appears (bright screen) the picture got zoomed and gone dark despite the game still running as the sound continue.

.

.I reduced contrast knob on the front remote board (inside control panel) to almost lowest level to keep the screen running.
The picture is too dissolve to play. Everytime I increase contrast to mediocre level the picture got zoom and vanished.
.

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Please help!

 

[skate323k137]

Have you tried turning down the "screen" adjustment on the flyback? Barely turn it each time, tiny rotation makes a difference.

 

[koki]

Have you tried turning down the "screen" adjustment on the flyback? Barely turn it each time, tiny rotation makes a difference.

You mean this "Screen pot" ? If so, yes I adjusted it not help.

 

[triforce7770]

Check for a cold solder joint on the contrast pot on the remote board? I had this sorta on my astro city. it was dim than gets bright, would flicker around too. I did a full reflow on the remote board and the pots on the side of the monitor chassis as well.

 

[skate323k137]

You mean this "Screen pot" ? If so, yes I adjusted it not help.

Yes, that one. Just had to rule that out.

 

[koki]

Check for a cold solder joint on the contrast pot on the remote board? I had this sorta on my astro city. it was dim than gets bright, would flicker around too. I did a full reflow on the remote board and the pots on the side of the monitor chassis as well.

I will try !

 

[GeekMan1222]

The image goes completely black or does it dim after the title screen gets really bright and blooms out from the brightness???
(that almost sounds like something being over driven, why we dont know yet)

I agree to check the solder joints on color / contrast and sub contrast and brightness pots though. These get mechanical forces applied to them over the years and the solder joints can fail because of this.

Always a good idea to check and reflow them if needed especially if you have your chassis removed to do work on it.

 

[koki]

The image goes completely black or does it dim after the title screen gets really bright and blooms out from the brightness???
(that almost sounds like something being over driven, why we dont know yet)

Apparently it completely black. I checked at the cathode tube, the heater stop working until turn off/ turn on back again.

 

[GeekMan1222]

Okay so it just cuts the picture out and the heater loses voltage??? I was worried about that.

That sounds like a high voltage shut down or a protection mode then possibly.

If another more vetted repair person can vouch here first then I would also check your B+ voltages then.

Because color and contrast is almost never related to capacitors.
However your B+ voltages can be, though I don't see that happen very often.

The value of your B+ may have changed with the new capacitors and it may be over driving one of the circuits or components, then the chassis enters a safety shut down to prevent damages.

But please DO NOT just jump in and start messing with your B+ circuit or values unless you know the correct test points and voltage values and what you are doing.
Messing around with the B+ circuit incorrectly can and WILL cause blown fuses, regulators, passives, Horizontal Output Transistors, etc.

So again if someone else here with personal experience working on the B+ circuits on a MS2930 can chime in that is appreciated.

 

[koki]

Yes, that one. Just had to rule that out.

I double checked the screen pot last night. The picture became darker when I turn counter-clockwise, seems like contrast improve a little bit but the picture loss details in gray area (all resulting in black). However, when the screen "flash" the tube still shutdown.

 

[koki]

Okay so it just cuts the picture out and the heater loses voltage??? I was worried about that.

That sounds like a high voltage shut down or a protection mode then possibly.

If another more vetted repair person can vouch here first then I would also check your B+ voltages then.

Because color and contrast is almost never related to capacitors.
However your B+ voltages can be, though I don't see that happen very often.

The value of your B+ may have changed with the new capacitors and it may be over driving one of the circuits or components, then the chassis enters a safety shut down to prevent damages.

But please DO NOT just jump in and start messing with your B+ circuit or values unless you know the correct test points and voltage values and what you are doing.
Messing around with the B+ circuit incorrectly can and WILL cause blown fuses, regulators, passives, Horizontal Output Transistors, etc.

So again if someone else here with personal experience working on the B+ circuits on a MS2930 can chime in that is appreciated.

Thank you for your assumption. Waiting for more info about this.

 

[GeekMan1222]

I double checked the screen pot last night. The picture became darker when I turn counter-clockwise, seems like contrast improve a little bit but the picture loss details in gray area (all resulting in black). However, when the screen "flash" the tube still shutdown.

Yes this really sounds like some kind of HV shut down or something. Like when the image increases in brightness a circuit somewhere is being over driven.
But CRT chassis's are a bit complex theres a multitude of things it could be, sometimes there is no easy answer it takes time to discover the faults or the root cause.

 

[koki]

I solved this issue. The ABL was culprit!!
ABL stands for Automatic Brightness Limiter. Increasing this knob on Chassis (it placed on right hand side from behind along with other knobs) and the issue solved.

 

[hoagtech]

I solved this issue. The ABL was culprit!!
ABL stands for Automatic Brightness Limiter. Increasing this knob on Chassis (it placed on right hand side from behind along with other knobs) and the issue solved.

I would love to see where this is located.

Do you mind sharing a pic on the chassis?

 

[koki]

 

[hoagtech]

Thanks. I tried that unfortunately.

Definitely turn this knob during testing if your tube isn't blown though..