[TV] Re: Zenith PVR5263RK - Need service manul and/or advice

["harry fogarty" <snoopys2002@xxxxxxxxxxx>]

http://schematics.myvnc.com/



Harry Fogarty
Harry`s Electronics
#4- 1144 MacKenzie Rd. North
Williams Lake
British Columbia
Canada
Tel: (250)-
Fax: (250)-




From: Rick <rick@xxxxxxxxxxxxxxxxxx>
Reply-To: tv@xxxxxxxxxxxxxxx
To: TV@xxxxxxxxxxxxxxx
Subject: [TV] Zenith PVR5263RK - Need service manul and/or advice
Date: Mon, 04 Apr 2005 15:14:05 -0700

Hello, I have a Zenith 52" rear projection TV.
Would somebody please help me obtain a service manual or schematics for
this TV?
I have tried from a couple of places but met dead ends.

The problem I am having is hard to explain but I will do my best.

What follows is a long account of everything I have observed and tried
so far.

First the convergence is way out of whack and although I get slight movement
when adjusting the POTs on the convergence board, it's nowhere near
enough to
bring it back into whack =)

Second, after the TV warms up, the voltage supplied to the convergence
board and convergence amplifier
(same circuit) becomes "unstable."  On a scope the line representing
this DC voltage will begin to bounce slowly
at first, then more rapidly (up to 2 or 3 times per second) and the
amplitude of this oscillation increases.

Since this distortion is in the convergence circuit, it manifests as
picture movement on the screen and affects all three
CRTs.  As the TV warms up and the voltage begins to drift, the top of
the screen will bow down then bounce in time
with the fluctuating voltage.

I visually inspected all components, especially resistors, and did not
find any obviously burned or otherwise expired components.
Next I took a can of air used it to cool parts in suspect places.  I
found a couple transistors and a resistor, all near each other, that
when cooled slowed or even stopped the strange voltage fluctuation.
Next I replaced the parts thinking they may have tired out, but the
problem persists.  Now I suspect too much current is going through that
section of the circuit for whatever reason and blowing air over the PCB
only cures the symptom, not the underlaying problem.

The front convergence board with the POTs has a Disable jumper to
disable the convergence correction.  Setting this jumper will
immediately stop the voltage oscillation.  Upon re-enabling the jumper,
the voltage will be stable for a few seconds and then ramp back up to
full oscillation.

Disconnecting just the BLUE input to the convergence amplifier will stop
the bouncing and then the red and green convergence adjustments have
much more effect on the picture than with the blue input connected.

Disconnecting the output coils of any of the RGB amplifiers stops the
bouncing but probably only because of reduced current draw through the
whole system.

I replaced the STKs which solved nothing, but neither did it break anything.

At this point I feel like I'm just shooting in the dark (and especially
without a schematic).
Somebody please help!

-Rick
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