[TechAssist] Re: JVC TV model AV27CM3- top half of screen stretched with foldover [SECOND POST]
- From: "Phillip R. Hull" <phil245@xxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Tue, 8 Oct 2002 11:21:40 -0400
I always seem to have trouble when I use a Generic Vert IC's esp SK's
Phillip R Hull
phil245@xxxxxxxxxxxxx
----- Original Message -----
From: "Peter oliver" <oliver_peter1@xxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Tuesday, October 08, 2002 10:33 AM
Subject: [TechAssist] Re: JVC TV model AV27CM3- top half of screen stretched
with foldover [SECOND POST]
>
> IF you have ever worked on a sony xbr that has had a jungle ic problem the
> output had an extra blip in the center of the waveform. Is it possible
that
> the input signal from the video jungle is bad. As for gerneric IC it
> shouldent matter LA7838 is made by sanyo if you buy from JVC they bought
it
> from sanyo put it in a bag and put their part number on it and mark up the
> price. You could try another gerieric as occasionally there is a bad one
> (<1% I've found) but never have seen a whole batch even when buying bulk
> ones 10+ at a time for $0.99 ea or less.
>
> Peter Oliver
> Tucson Radio TV
>
>
> From: Gary McCartney <number63@xxxxxxxxxxxxx>
> Reply-To: techassist@xxxxxxxxxxxxx
> To: techassist@xxxxxxxxxxxxx
> Subject: [TechAssist] Re: JVC TV model AV27CM3- top half of screen
stretched
> with foldover [SECOND POST]
> Date: Tue, 08 Oct 2002 01:20:43 -0400
>
>
> 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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