[TechAssist] Re: GE 31GT658 chassis CTC187CK regulation

CR4109 operates at 7.4 vots- OK
C4407 checks good, this is in the pin circuit and I can't see how it would
cause regulation problems, but it was checked routinely when the HOT was
found to be shorted.  BTW, the HOT collector waveform is right on in timing,
clean and stable.

C4105 is where?  I may need to check this.  I don't see it in the PS diagram
that I have but if it is in the primary of the PS ( as the number suggests)
it has been checked, as I have checked every component there.

CR4112 could be leaky, but it checks ok out of circuit.  Its related caps
C4128 & C4135 check good.

R4124 is right on.

The IC that I used was a generic.  I have used them many times with no
problem.  The HOT was an RCA, as was the rectifier.  I am leaning toward a
bad IC.

Leonard G. Caillouet
Service Manager
Electronics World
Gainesville, FL
352-332-5608
352-332-5668 (fax)


----- Original Message -----
From: "Gemini Computer & TV" <geminitv@xxxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Thursday, February 27, 2003 2:49 PM
Subject: [TechAssist] Re: GE 31GT658 chassis CTC187CK regulation


>
> The very first things I would suspect are CR4109 (7.5 volt zener diode),
> C4407 (0.041UF, 400V), and C4105.
> Aside from that, next would be U4101, CR4112, C4128, and C4135. I must ask
> if you used OEM parts or did you use subs? The part numbers are as
follows:
>
> CR4109 - 215490
> C4407 - 218492
> C4105 - look in set to see which you have (if it is 10mfd/200v then the
part
> number is 214743 and if it is 22mfd/200V then the part number is 225667).
> U4101 - 223948
> CR4112 - 140971
> C4128, C4135 - 102230 (470pf, 500v)
>
> Bob Waterman, CET® #RI-28
> Master Technician License #9109
> Service Manager
> Gemini Computer, TV, & Security Alarms
> (508)695-7302
> (508)695-7769 FAX
> geminitv@xxxxxxxxxxxxxxxx
> geminitv@xxxxxxx
>
>
> ----- Original Message -----
> From: "Leonard G. Caillouet" <lcaillo@xxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Thursday, February 27, 2003 11:25 AM
> Subject: [TechAssist] GE 31GT658 chassis CTC187CK regulation
>
>
> >
> > Replaced the HOT, CR4106P (B+ rectifier Part # 243636), U4101V
> (STK730-030)
> > and line fuse.  Now the set runs but regulated B+ is 145.5 Vdc.  It
> appears
> > to have a little trouble regulating on scene changes.  Have checked all
> > components related to the regulator and found only R4105 was off by a
> couple
> > of ohms, so I replaced it with no effect.  I am thinking that I have a
bad
> > regulator IC but just want to check to see if anyone has run into this
> > before or is anyone is more  familiar with this circuit than I am (which
> I'm
> > sure is the case).  I am working with Bob Rose's book and do not have
the
> > Thompson service literature on this chassis, so if anyone can fill in
the
> > blanks I'd appreciate it.
> >
> > Pin 1 is -40.7 Vdc which is within the range it should be.  This means
> that
> > the error amp in the chip is keeping the voltage at the reference level,
> so
> > I assume the chip is just bad.  Am I missing something or is the voltage
> at
> > pin 2 too far off?
> > Pin 2 is -30.5 Vdc, I am not sure what it should be.
> > Ground is good at pin 3
> > Pin 7 is -.5 Vdc  I thought this should be more negative but not sure.
> > Pins 11&12 are 145.5 Vdc
> >
> > The HOT does not seem to be getting very hot but I am not running it for
> > very long before shutting it down.
> >
> > Thanks
> >
> > Leonard G. Caillouet
> > Service Manager
> > Electronics World
> > Gainesville, FL
> > 352-332-5608
> > 352-332-5668 (fax)
> >
> >
> >
>
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