[TechAssist] Re: RCA PTK-171ACC PTV, pulses
- From: Dennis Viereck <wa6ati@xxxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Mon, 14 Jan 2002 19:27:24 -0800
I'm surprised that the brown Isn't the dribblings from the rubber bumpers. If
the serial # starts with 3 then I would suspect that it is, in fact, liquid
contained in the rubber bumpers.
Since V & H deflection are present then you are probably experiencing a Scan
loss shutdown event. I do not recommend defeating the circuitry for fear the
CRT's could be damaged.
Good Luck
Dennis Viereck
gulftech@xxxxxxxx wrote:
> Dennis,
>
> Thanks for those comments. To answer your questions: 1. What make you
> sure it is deflection related? Would you believe SWAG (Stupid
> Wild-Axx-Guess)? Not really. My ears took me there. I could hear
> something like a relay closing and opening on that board at the times the
> crt's would flash. 2. Is it loosing High voltage? No, according to my
> friend. 3. Is it loosing vertical or horizontal sweep? Again, not
> according to Kenny.
>
> I had been trying to help him over the phone for a couple of weeks. I
> saw it "in the flesh" today for the first time, and then only briefly.
> There was something spilled on the board where the A/V I/O pcb connects
> to the main board. It was quite a mess--brown, sticky substance along
> the length of the board. Don't think it is the cause of the mentioned
> problem, but clearly could cause any number of problems. (It is similar
> in appearance the the brown goo from the rubber bumpers in the RCA PIP
> module I mentioned a week or two ago, or like brown Mitsubishi glue, but
> tacky.) I had him take the casket with him to remove the board and
> thoroughly clean it up. He will bring it back in a day or two, along
> with the service manual. We will tackle it again then.
>
> Just talked to my friend. He said there was much more that I could see.
> He had to remove a couple of stand-up boards to clean the mess. Said it
> made no difference in the flashing.
>
> Thanks for the helpful info. I will let you know what we find later in
> the week.
>
> Ken Smith
> Gulf Technical Services
> 3034 Gulf Breeze Parkway
> Gulf Breeze, FL 32561
> 850-934-8324 (Voice) 850-932-0819 (Fax)
>
> >
>
> On Mon, 14 Jan 2002 10:33:05 -0800 Dennis Viereck <wa6ati@xxxxxxxxxxxxxx>
> writes:
> >
> >
> > What make you sure it is deflection related?
> > Is it loosing High voltage?
> > Is it loosing vertical or horizontal sweep?
> >
> > This unit has a scan loss circuit on the PTV adapter board located
> > under the
> > green CRT. If the scan loss detector senses the loss of either
> > deflection
> > element the raster will be muted but the High voltage will still be
> > present.
> > Raster is muted on each CRT by forcing G1 to "0" volts. It normally
> > is at 18
> > ~ 25 volts. A failure in the sensor circuit will cause the symptom
> > you are
> > experiencing.
> >
> > Make sure you have the 3 "Must Haves" High voltage, Vertical, &
> > Horizontal
> > deflection before attacking the PTV adabter board. There are two
> > compactors &
> > 3 transistors on that board this contain most of the scan loss
> > circuitry.
> > Make sure this circuit is functioning correctly.
> >
> > Another thing that will cause scan loss shut down is the PTV Aux.
> > Power
> > supply. If it is shutting on and off it will also mute the raster as
> > in the
> > case of the deflection circuits.
> >
> > Good Luck
> > Dennis VierecK
> >
> > gulftech@xxxxxxxx wrote:
> >
> > > A friend (fellow tech) has a problem with this RCA PTK171. When
> > power is
> > > applied, the set powers on and pulses. All three CRT's flash on
> > for
> > > about half a second, then turn off, back on, back off, etc...
> > With the
> > > cable connected, the video image is present.
> > >
> > > The HV splitter has been replaced and the deflection pcb was
> > rebuilt by
> > > PTS. I believe the problem still lies in the deflection board,
> > but am
> > > not familiar with this chassis.
> > >
> > > Before he sends the board back to PTS, I want to check with you
> > guys for
> > > any other suggestions.
> > >
> > > Thanks,
> > >
> > > Ken Smith
> > > Gulf Technical Services
> > > 3034 Gulf Breeze Parkway
> > > Gulf Breeze, FL 32561
> > > 850-934-8324 (Voice) 850-932-0819 (Fax)
> > >
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