[TechAssist] Re: Rca PTV P46770CK PTK169PAAS chassis No contrast update FIX
- From: "Gemini Computer & TV" <geminitv@xxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Thu, 29 Apr 2004 09:01:07 -0400
Excellent work Al!
Bob Waterman, CET® #RI-28
Master Technician License #9109
Service Manager / Parts Manager
Gemini Computer, TV, & Security Alarms
(508)695-7302
(508)695-7769 FAX
geminitv@xxxxxxxxxxx
geminitv@xxxxxxx
www.geminicomputertvsecurityalarms.com
----- Original Message -----
From: "al m" <ampm@xxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Thursday, April 29, 2004 8:49 AM
Subject: [TechAssist] Re: Rca PTV P46770CK PTK169PAAS chassis No contrast
update FIX
> Well I found it. I worked my way back from the micro to see why the
contrast
> Voltage was being held at 4.5V. disconnected parts one at a time to see if
> the voltage would go high. When I disconnected the beam limit transistor
the
> voltage went high. Back tracking I found that when I took out R2721 27K
1/2w
> it broke in half. Replaced this and same thing. Went back further and
found
> a 10V pulse on R2721. Checked R4713 and it was 58K was supposed to be 68K.
> Changed that no help. Checked C4701 and when I got it out the one leg came
> out. Replacing this cut the pulses to nothing and the 8.3V that was on
R2721
> went up to 9.5 volts and the contrast voltage went high. I replaced R4703
a
> 3.3ohm 3W resistor because when I moved it that one broke in half too.
Also
> I replaced C4755 1mf 250V on the high voltage regulator board for high ESR
> and C4758 for good measure on the beam limit line. So there you have it,
> there is no pulse on R2721 and the voltage on this has to be 9.5 for the
> circuit to work. WHOOPEE!!!!!
> Al Marquardt
> ampm@xxxxxxx
> Al Marquardt Electronic Repair
> 206 W Main
> Girardville Pa. 17935
> ----- Original Message -----
> From: "al m" <ampm@xxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Wednesday, April 28, 2004 5:46 PM
> Subject: [TechAssist] Rca PTV P46770CK PTK169PAAS chassis No contrast
update
>
>
> > this PTV the contrast will not adjust. I have found that if I disconnect
> the
> > Beam limit transistor the contrast adjusts.checked all parts in that
> circuit
> > and all check OK. Now the big question. Does anyone know what waveform
> > should be on the line that comes from the high voltage Regulator board
to
> > the main board on E25? I have checked the voltages on the transistors
and
> > the transformer waveform looks good on pin 2. It must have something to
do
> > with the amplitude of the signal going back to the beam circuit. Can
weak
> > picture tubes cause this to happen? Have very little experience with
these
> > beam circuits. Thanks.
> > Al Marquardt
> > ampm@xxxxxxx
> > Al Marquardt Electronic Repair
> > 206 W Main
> > Girardville Pa. 17935
> >
> >
> >
>
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