[TechAssist] Re: JVC TV AV2749S, yoke arcing at CRT neck
- From: Kevin <kevintv@xxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 13 Aug 2003 23:11:09 -0700
The burn mark was caused by the yoke shorting so I don't see how there
could be any arcing from the tube. If there was arcing the vacuum in
the picture tube would be gone and the tube would be useless. The glass
is thinner at the point that you scraped the burn mark off so putting
some epoxy there would be a good idea. One thing I am not sure about is
if there was dag coating that you removed when scraping the burn mark
off. This may have to be painted back on. HTH
Kevin Wilks
Kevin's TV & Video Repair
Penticton BC Canada
kevintv@xxxxxxx
-----Original Message-----
From: techassist-bounce@xxxxxxxxxxxxx
[mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of Gary McCartney
Sent: Wednesday, August 13, 2003 10:17 PM
To: techassist@xxxxxxxxxxxxx
Subject: [TechAssist] JVC TV AV2749S, yoke arcing at CRT neck
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.
--
Gary McCartney
McCartney Electronics
Guelph Ontario Canada
Est. 1984
email: gary (at) number63.ca
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