[TechAssist] Re: Update:Sony KPR41EXR95 Dead
- From: Dennis Viereck <wa6ati@xxxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 14 Nov 2001 09:19:59 -0800
Jeff:
You have no horizontal sweep. Just because you have high voltage does not mean
you will have horizontal sweep.
This is a AP chassis where you have the high voltage board "N board" stacked on
top of the main power supply module "G board".
The horizontal output is run from a -135 volt source from the G board. The -135
is fed to the pincushion driver Q508(c) and the Pin driver Q508(E) feeds a
varying voltage to the Emitter of the Horizontal output Q502(E). Q502(C) is tied
to ground indirectly through the horizontal output transformer T501 all located
on the "A" board. So don't condemn the Horizontal output transistor if you
measure a short to ground on it's collector.
The voltage at Q502 varies about 25 volts peak to peak at the vertical rate to
compensate for pincushion error. Typically the average DC voltage at Q502(E) is
-105 VDC.
If you are missing this voltage then check the components in the pin driver
circuit. If certain components open Q508 turns off and removes the voltage from
Q502. Thus no horizontal sweep.
Dennis Viereck
Shoreline Electronics wrote:
> Make : Sony
> Model : KPR41EXR95
> Problem : Originally was dead...no relay click. Pulled power supply board &
> found Q603 & D605 shorted. Replace both of those AND Q614 for good measure.
> Resoldered many cracked solder connections on this board AND HV/Sweep
> module.
>
> Now we have power and HV ( I can hear it come up)...but all we get is a
> little vertical squiggly line in bottom of each CRT. We have only left it
> on for a brief second to prevent a burn.
>
> I pulled the boards again & double checked for solder bridges & missing
> connectors....we didn't miss a thing.
>
> Maybe this problem is what caused the failure in the first place? Any idea
> on what may cause this?
>
> Jeff Stielau
> Shoreline Electronics Repair
> 125 Beechtree Lane
> Westbrook,CT 06498
> 860-399-1861 Voice
> 860-664-3535 Fax
> jstielau@xxxxxxxx
>
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