[TV] Re: Zenith PVR5263RK - Need service manul and/or advice
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[TV] Re: Zenith PVR5263RK - Need service manul and/or advice
OK everyone, here is an update: Some things fixed, some things possibly
not right...
I took John's advice (below) and checked the voltage at the diodes. The
mess was still there
on the -26v diode so I replaced the diode and filter cap. The set was
stable for a long time. I thought
the problem was solved but eventually the "bounce" came back.
I decided to check the +26v side and noticed that the convergence board
was not getting +26v, but it was
there at the diode. Blown fuse on the +26v supply. I hadn't noticed it
before because the glass window was
covered with a blob of adhesive. I determined that dead side of the fuse
wasn't grounded out and jumped it with
a fused ammeter to see what would happen. Current through the meter was
not high so I jumped the blown fuse with
a wire. Of course now the convergence POTs have significant affect on
the TV compared with before. Also,
the odd pulsating has not returned on the -26v supply. I let the TV warm
up for quite some time and all seems well.
There does seem to be some noise on the +26v supply, however, so I will
replace it's filter cap.
There's something up with BLUE, maybe someone has seen this before.
When I pull up a PIP box or the menu, blue is missing from the vertical
lines of any borders/boxes.
If I go to the convergence adjustment setting in the menu, the two
vertical lines are not white because there is very
little blue in them. If I then turn off the red and green CRTs the
vertical lines for blue are tiny slivers compared to the
thick lines of R and G. Also on this menu all the text at the top
("Press FREEZE to select the color...") is in blue only and
is virtually unreadable because of the lack of vertical blue lines.
Thanks everyone, I'll keep you posted...
-Rick
rick@xxxxxxxxxxxxxxxxxx wrote:
>Thanks John,
>
>-26v is the line that pulsates. I looked at it on the scope last night
>and it looks like it drops to ground potential for a split second, then
>quickly rises back up and repeats.
>
>I will check the diode and perhaps filter cap esr and post results.
>
>Thanks,
>Rick
>
>
>
>>Rick, I'm sending this message again because I don't think it went
>>through.
>>But all I have left on this one is to check cr3419 and cr3420 and make
>>sure
>>you have a clean waveform. This is you + & -
>>26volts for convergence. somtimes these diodes break down under a load or
>>the filters get dry and do not filter right and there is ripple.
>>good luck on this one
>>john
>>
>>
>>
>>>From: Rick <rick@xxxxxxxxxxxxxxxxxx>
>>>Reply-To: tv@xxxxxxxxxxxxxxx
>>>To: tv@xxxxxxxxxxxxxxx
>>>Subject: [TV] Re: Zenith PVR5263RK - Need service manul and/or advice
>>>Date: Mon, 04 Apr 2005 19:07:32 -0700
>>>
>>>No dice...
>>>I pulled the two resistors and checked them out-of-circuit. They were
>>>within tolernce and physically look as good as new.
>>>Just to be sure, I measured resistance while accosting them with a heat
>>>gun (not a hair dryer, but a real heat gun).
>>>They both held up remarkably well.
>>>
>>>Thanks for the suggestion!
>>>
>>>John Conti wrote:
>>>
>>>
>>>
>>>>Rick, on the 9-1302 check two resistors, they are r3243 (110k 1/2 watt
>>>>
>>>>
>>>and
>>>
>>>
>>>>r3244 (82k 1/2 watt)
>>>>they either change values or open up. They are located next to the
>>>>
>>>>
>>>upright
>>>
>>>
>>>>board that stands vertical. I think your having the same problem that I
>>>>
>>>>
>>>had
>>>
>>>
>>>>a few months ago and if so, drove me crazy before I located the
>>>>
>>>>
>>>problem.
>>>Let
>>>
>>>
>>>>me know how you came out on this, for if thats the problem it will sure
>>>>
>>>>
>>>save
>>>
>>>
>>>>others a lot of time.
>>>>
>>>>good luck
>>>>john
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>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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>>>>>
>>>>>
>>>>>
>>>>>
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>>>>
>>>>
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>
>
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