[TechAssist] Re: JVC TV AV2749S, yoke arcing at CRT neck [UPDATE]
- From: Gary McCartney <gary@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Fri, 15 Aug 2003 16:29:21 -0400
George, I tried a 0.0051 1600V and the picture narrowed by about 3/4"
but the HOT collector waveform went from 1200V p-p (with original caps
installed) to 1250 Vp-p. I have put the original cap back in to run the
set for a while so I can measure the HOT temp. then I'll run it with the
0.0051uF and measure the temp.
Is 1200V p-p too high for these JVC's? I think most TVs are 1050 to
1100V p-p.
Gary McCartney
McCartney Electronics
Guelph Ontario Canada
Est. 1984
email: gary (at) number63.ca
George wrote:
>
> Gary,
>
> Try an .005 for the .0062 to start and then you can go from there just keep
> an eye on the HV rise as you reduce the value to make sure that it remains
> within the limit.
>
> George
> Afana Electronics
> Moreno Valley, CA
>
> ----- Original Message -----
> From: "Gary McCartney" <gary@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Friday, August 15, 2003 10:47 AM
> Subject: [TechAssist] JVC TV AV2749S, yoke arcing at CRT neck [UPDATE]
>
> > I have this set running now. I applied epoxy to the spot on the glass
> > and covered it with tape. I have a good picture except for one problem.
> > It has too much width, about 1 to 1 1/2 inches too much. The geometry
> > look fine though. The used yoke I installed did not have a JVC number on
> > it and did not have the same connectors, but the yoke itself appeared to
> > be the exact same. I realize that even though it looked exact the
> > winding could be slightly different.
> > Assuming the new yoke is the same as the old, I have removed the 2 blue
> > caps C525 and C524 from the HOT collector to ground. Can anyone identify
> > the valuse of these caps please?
> >
> > C524: labelled PH7001H 1.6KV
> > C525: labelled PH6201H 1.6KV
> >
> > I believe these are 0.007uF and 0.0062uF but I'd like this confirmed if
> > possible.
> > SAMS is having techical problems with their web site else I'd look up
> > the SAMS number for this set.
> >
> > What else can cause too much width in this chassis? Is it safe to change
> > the value of one of these caps enough to narrow the picture up a bit? I
> > am concerned that perhaps the yoke burnt in the first place because of
> > to much current going through it.
> >
> >
> > Thanks for any help.
> >
> >
> >
> >
> > Gary McCartney
> >
> > McCartney Electronics
> > Guelph Ontario Canada
> > Est. 1984
> > email: gary (at) number63.ca
> >
> >
> >
> >
> >
> >
> > My Original message:
> >
> >
> > I have this JVC TV model AV2749S in the shop and I have found that the
> > yoke is shorted where it wraps around the neck of the CRT, causing a
> > black burn mark on the glass. I took a knife and scraped it off but
> > there is a slight crater in the glass now, maybe 1/64 of an inch or so
> > deep. Is this a weak spot from now on, meaning that this spot will be
> > suseptable to more arcing in the future or worse yet, a crack in the
> > neck? Can I apply some epoxy to the spot to give it insulation, or
> > should this tube be scrapped? I have a used yoke which looks to be in
> > great shape which I can use in the set so I hate to tell the customer it
> > is garbage.
> >
> >
> > Here is a photo of the mentioned spot on the glass:
> >
> > http://www.number63.ca/tube-neck.jpg
> >
> >
> >
> > How I found the bad yoke:
> >
> > The set came in with F902, 1.25 Amp fuse open. I couldn't find any
> > defective parts so I installed a new fuse in case that was the only
> > problem. Pressed power button and saw LED blink and that was all- the
> > fuse was open again. Next, I looked up tips and found one that mentioned
> > the yoke as a possibility, so I pulled the CRT board and the yoke
> > connectors. The LED came on and stayed. Then I reconnected the hor.
> > winding and put a new fuse in. Had to use 1.5A instead of 1.25. I used a
> > variac set at 90VAC and plugged it in. The LED came on and I heard the
> > arcing and saw smoke coming from the yoke/ CRT neck.
> >
> >
> > Thanks for any help.
> > --
> >
> >
> >
> >
> >
> >
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