[TechAssist] Re: JVC TV model AV27CM3- top half of screen stretched with foldover [SECOND POST]
- From: "LeRoy Westlund" <llw@xxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Mon, 7 Oct 2002 20:45:37 -0600
Gary,
I see that you didn't list C422 as one you have checked.
It is a 1ufd. @ 35 volts (Tentanilum).
Worth a try, maybe ?
HTH,
LLW
LeRoy Westlund
Westlund TV & Electronics " It's such a pretty world
93 North Main today !....
Centerfield, UT 84622-0087 Look at the Sunshine. "
Ph./Fax 435-528-3822 :-)
mailto:LLW@xxxxxxxxxx
-----Original Message-----
From: Gary McCartney <number63@xxxxxxxxxxxxx>
To: techassist@xxxxxxxxxxxxx <techassist@xxxxxxxxxxxxx>
Date: Monday, October 07, 2002 1:17 PM
Subject: [TechAssist] JVC TV model AV27CM3- top half of screen stretched
with foldover [SECOND POST]
>
>I still haven't solved this set.
>
>Measured B+ to vertical chip. I get 28.7V with 1.5 V p-p of ripple.
>Replaced D534 rectifier and C534 filter cap but no change in ripple.
>Also measured output of 12 V regulator I changed earlier. Measured
>11.94V, with no noticable ripple. Scoped input pulse to vert. chip at
>pin 2 and got nice clean square wave at 8V p-p and very high duty cycle,
>maybe 95%. I don't have waveforms or schematic in print to verify my
>measurements to be correct. Scoped vertical output waveform on pin 12
>and get 55V p-p pulse with a blip in the slope which doesn't look
>normal. I drew a picture of this and posted it for you to view:
>
>
>http://www.number63.ca/waveform.jpg
>
>
>
>Also replaced yoke. I found one in my stock which appears to be the
>exact same yoke only out of a Philips set and the connectors were a bit
>different. I switched the connectors from the JVC yoke and tried it. No
>change in problem. If anyone is interested, here are the yoke numbers
>(from the stickers on the yokes). Sorry I don't have record of the
>Philips TV model.
>
>Original JVC yoke: CE20240-AOA
>Philips yoke: 362075-7
>
>
>Changed a few more small caps and resistors in the vertical section.
>Problem has not improved. Any help appreciated.
>
>
>
>Gary McCartney
>
>McCartney Electronics
>7134 Fife Rd, RR 7
>Guelph Ontario Canada N1H 6J4
>Fax: (519)821-1530
>email: number63 (at) inetsonic.com
>
>
>
>
>
>My original message:
>
>
>This is a 27" JVC tV model AV27CM3. No Sams listed but there is one for
>model AV27CM4, # 3379.
>
>The vertical linearity is off all the way from the bottom but once it
>hits the center of the screen, it starts stretching so bad that there is
>about 3" of foldover.
>
>Working without a schematic. I have replaced:
>
>IC421, LA7838
>IC422, 12V regulator
>ZD425, 75V 1W
>C425
>C426
>C430
>C421
>C536
>C530
>
>I removed D421 and checked it but I don't know what it is. marking on it
>is 3N. It looks like a glass 1W zener but symbol on board shows it as a
>regular diode. Checks ok anyways.
>
>Does anyone have a schematic of the vertical circuit plus hopefully
>waveforms?
>
>Thanks for any help.
>--
>
>
>
>Gary McCartney
>
>McCartney Electronics
>7134 Fife Rd, RR 7
>Guelph Ontario Canada N1H 6J4
>Fax: (519)821-1530
>email: number63 (at) inetsonic.com
>
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