Re: Stumped with a K7000

From: John Robertson <>
Date: Sat Apr 03 2010 - 12:40:53 EDT

RCade Resources wrote:
> Hey guys,
> OK, here's the deal...
> I have a 19K7901 that I received in non-working order. The previous owner
> had capped it, replaced the flyback and HOT. Turns out the HOT was not
> insulated, hence no workie. I replaced the HOT, and insulated it, and the
> monitor worked fine for a while, with the exception of occasional flickers
> (like the HV shutting down momentarily).
> Well, it decided it didn't like working here anymore and quit.
> I pulled the chassis and started testing it out. The HOT had died again,
> and the voltage reg at IC4 appeared to be shorted. I'll skip a bunch of
> boring details, but here's where I'm at now:
> Pulled IC4, and it is not shorted out of circuit. I ordered some to have on
> hand anyway, but I think this one is OK.
> If I power the chassis up on my bench, B+ only measures around 18VDC, IIRC.
> I have pulled the HOT and IC4 and powered the chassis without them. The pad
> for pin 1 of IC4 is still only getting around 24VDC. The left-hand side (on
> the schems) of R103 is getting 120-ish, though.
> I clipped the blue lead off R301/302 (the right-hand side on the schems),
> and powered it up again. Now pin 1 where IC4 should be starts off around
> 70VDC and slowly trickles up to 120-ish. Powering down, that pin slowly
> trickles back down.
> On a whim, I replaced C55, C56, and C57, and reconnected the other end of
> R301/302. Still only getting about 24VDC at the pad for pin 1 of IC4.
> Thoughts?
> Thanks,
> Rob
Regulator pass resistor blown?

John :-#)#

John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
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Received on Sat Apr 3 12:41:00 2010

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