[TechAssist] Re: GE 31GT658 chassis CTC187CK regulation

What do you mean by "...have a little trouble regulating on scene
changes..."?

These sets do not have a high voltage regulator, and as such going to/from
light/dark scenes the pic will change size horizontally a little.

Do you have a peak hold function on a meter?

Wayne Vanaman
Omega Electronics
6904 W Fairfield Dr
Pensacola, Fl.  32506-3310

Wayne@xxxxxxxxxxxxxxxxxxxxx
WWW.PensacolaTVRepair.Com

850-456-5995 voice
850-458-6369 fax


----- Original Message -----
From: "Leonard G. Caillouet" <lcaillo@xxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, February 28, 2003 10:10 AM
Subject: [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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