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Main => Monitor/Video Forum => Topic started by: smalltownguy on September 04, 2010, 09:47:37 am

Title: Disco 19" with flagging - need a diagnosis - new caps, still not working
Post by: smalltownguy on September 04, 2010, 09:47:37 am: I have a 19" monitor in a Super Baseball game that needs some attention. The tube is a Phillips 19VKUP-22, and the chassis is a Disco DMC Model 2090DT-2A. Manufacture date is 1982 -- this monitor was originally in an Atari Food Fight cabinet - in fact the cab itself is a FF conversion.

I've got some annoying foldover going on here, and would everyone's opinion as to what I need to do. I've already tried adjusting all of the vertical and horizontal pots -- this is the best I can get. I suspect a cap kit is in order, but before I go any further, I thought I would ask for opinions.

Here's a video of the monitor in action:

19" Disco Arcade monitor with foldover issues (http://www.youtube.com/watch?v=YbQSbM8tdTI#)
Title: Re: Disco 19" with Foldover - need a diagnosis
Post by: qrz on September 04, 2010, 02:24:27 pm: thats flagging, rather than foldover.

anyway , there are likely a couple of 'lytic caps in the Hosc/drive circuit that have changed value/elevated ESR .

i'd need to locate a print in order to provide specific location numbers ...
Title: Re: Disco 19" with Foldover - need a diagnosis
Post by: smalltownguy on September 04, 2010, 02:33:48 pm: Yeah, Ken Layton over at KLOV mentioned caps too. I'll go ahead and shotgun the whole thing to be safe.
Title: Re: Disco 19" with Foldover - need a diagnosis
Post by: qrz on September 04, 2010, 04:58:12 pm: have a look at
c527 ( 33Uf/16v)
c533 (1Uf/50v)
c532 (10Uf/16v)
c005 (4.7Uf/160v)
c006 (22Uf/160v)

schematic also indicates a parallel res/cap combo on the sync in line ( pin9 ic401)
no location numbers/listed parts . so, likely NOT used
Title: Re: Disco 19" with Foldover - need a diagnosis
Post by: smalltownguy on October 05, 2010, 11:20:49 pm: I shotgunned this chassis tonight, but no change in the flagging. Any other ideas?

Could the horizontal width coil be causing this? It looks a bit flaky.
Title: Re: Disco 19" with Foldover - need a diagnosis
Post by: smalltownguy on October 28, 2010, 12:31:34 am: Replaced the filter cap tonight - now the colors look VERY nice, but there's still a bit of 'wave' going on:

Disco 2090DT-2A (http://www.youtube.com/watch?v=inmR2Dx_SzY#)

Can the width coil be causing this? I think it's pretty near broken completely.
Title: Re: Disco 19" with Foldover - need a diagnosis
Post by: qrz on October 28, 2010, 07:23:17 am: check/replace these caps in Vreg
c005 4.7/160v
c006 22/160

boost cap c706 4.7/250v
Title: Re: Disco 19" with Foldover - need a diagnosis
Post by: smalltownguy on November 03, 2010, 10:30:41 pm: Quote from: qrz on October 28, 2010, 07:23:17 am
check/replace these caps in Vreg
c005 4.7/160v DONE
c006 22/160 DONE

boost cap c706 4.7/250v DONE

No change.

What do I check next?

FYI, there's an extra ceramic capacitor soldered to the foil side of the neck board. Should this be there?
Title: Re: Disco 19" with Foldover - need a diagnosis
Post by: smalltownguy on November 10, 2010, 09:10:35 am: I also checked Q001, Q002, Q003 and Q901 tonight. None of them are leaking, all test OK.

Filter cap cap has also been changed, and I've double checked the B+ pot.

Still have a wavy picture -- what's next?
Title: Re: Disco 19" with flagging - need a diagnosis - new caps, still not working
Post by: smalltownguy on November 12, 2010, 05:27:04 pm: I'm going to check the B+ voltage once again tonight. If I had a faulty B+ pot, could that cause this issue?
Title: Re: Disco 19" with flagging - need a diagnosis - new caps, still not working
Post by: smalltownguy on November 20, 2010, 09:58:26 am: Ok, I went back today and started over with troubleshooting. I wanted to see what the B+ voltage was once again.

Measured 142.6!! Too high. Adjusting the pot does nothing. Do I need to replace the pot, or could something else cause the voltage to not be able to be adjusted?
Title: Re: Disco 19" with flagging - need a diagnosis - new caps, still not working
Post by: lilshawn on November 21, 2010, 05:21:51 pm: Quote
Adjusting the pot does nothing.

does it change 0.00 volts from one extreme to the other? or just very little. does "nothing" and does NOTHING are 2 completely different things.

a faulty regulator or voltage feedback circuit can cause NO VOLTAGE CHANGE, a faulty pot or failing component can cause "nothing" (LITTLE VOLTAGE CHANGE)