[TechAssist] Re: JVC TV AV2749S, yoke arcing at CRT neck [UPDATE]
- From: "Intrepid Video Support" <support@xxxxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sat, 16 Aug 2003 12:00:37 -0400
Gary,
May the replacement yoke have been for a 31" set?
Jeff Dougherty
Intrepid Video TV/VCR
263 S Front St
Steelton PA 17113
fax...717-564-4952
www.intrepid-video.com www.tech-repair.net
----- Original Message -----
From: "Gary McCartney" <gary@xxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, August 15, 2003 1:47 PM
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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