[TechAssist] Re: JVC TV model AV27CM3- top half of screen stretched with foldover [SECOND POST]
- From: "Tech Repair CD support" <support@xxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Tue, 8 Oct 2002 15:27:17 -0400
Gary,
I would doubt it, though may be possible.
Look for any CAP that begins with 500 series...check all caps off vertical
windings of yoke.
Jeff
FAX 717-564-4952
Intrepid Video & Electronics
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Harrisburg PA 17111-2055
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----- Original Message -----
From: "Gary McCartney" <number63@xxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Tuesday, October 08, 2002 1:20 AM
Subject: [TechAssist] Re: JVC TV model AV27CM3- top half of screen stretched
with
foldover [SECOND POST]
Leroy, thanks for researching that for me. Unfortunately it didn't solve
it. Someone sent me a partial schematic for a similar model, so
hopefully that will help me notice something. The waveforms I measured
seem to check out against the print, so thats good, except for the blip
on my output waveform. Do you think there is any chance that my brand
new generic LA7838 could be causing the exact same symptom as the
original IC?
Gary
LeRoy Westlund wrote:
>
> 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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--
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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