[TechAssist] Re: Question Thomson technical help.
- From: Paul <dntwntv@xxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 31 Dec 2003 13:30:46 -0800 (PST)
Jim You are right. I checked the voltage at pin 50 of U13101 and the 4.5v is
missing. I removed the resistor from the collector of Q11900 applied 4.5v to
base and sound came on. However it does not get full volume. Interesting that
the sound is normal and the mute works the way it is now. I will replace U13101
and see if everything works as normal. BTW that IC has been changed before. The
customer mentioned that someone had worked on this set in the house in the
past.Couldn't remember what the problem was at that time. I am amazed that
anyone would do all that in the house. It's a 36" set that is in his bedroom
with very little room to work, on top of a chest about shoulder high. Customers
mind might be a little fuzzy. Paul
Jim Myers <jr.myers@xxxxxxxxxxx> wrote:Obviously someone has modified the
circuit to hide a problem, that 0.81R
resistor should not be there. Pin 50 of U13101, the Syscon micro should be
high to bias the base of Q11900 to turn the transistor on and keep the
collector low. Pin 50 should toggle with the mute switch. Defeating the mute
circuit is also what causes it to have a loud pop when turned on or off.
This should NOT be ignored unless the owner doesn't want to spend the money
for a proper fix. The CTC197 schematic does not uses proper logic state
labeling, it shows U13101 pin 50 having 4.9 volts and is labeled "speaker
mute" with no bar while pin 5 of U11901 is labeled "mute" with no bar and
shows 24.6 volts. If pin 50 is high then pin 5 should be low since Q11900 is
an NPN inverter.
**************************************************
Jim Myers
Since 1972
Telrad Electronic Services Co.
Fort Wayne, IN 46815
*************************************************
----- Original Message -----
From: "Gemini Computer & TV"
To:
Sent: Wednesday, December 31, 2003 9:26 AM
Subject: [TechAssist] Re: Question Thomson technical help.
I have searched all my resources and can't find anything except for Q11900
itself but I see that has already been replaced. The only resistors I see
off the collector of Q11900 are R11904 (1K that goes to pin 5 of the audio
amp IC and R11926 (15K that goes to +31VS source in parallel with C11907
(1uf). What is the reference number of this .84 ohm resistor you mention
because it doesn't make sense to have that value resistor off the collector
of Q11900?
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@xxxxxxxxxxxxxxxx
geminitv@xxxxxxx
www.geminicomputertvsecurityalarms.com
----- Original Message -----
From: "Paul"
To:
Sent: Tuesday, December 30, 2003 9:12 PM
Subject: [TechAssist] Re: Question Thomson technical help.
> I have posted the problem and haven't come up with a fix. It is an RCA
ctc197A. There are apparently variations in this circuit because the
collector of the mute transistor Q11900 has a .84 ohm resistor to ground and
0 volts. If I lift that resistor I lose the sound. Other circuits show 31v
on the collector. The problem is a delayed loud pop in the sound when
plugged in and also when turned off. I have replaced the mute transistor and
a couple of caps in the supply for the sound. Several have tried to help and
I am not unappreciative, but maybe no one else has had this problem.
Paul
> "Phillip R. Hull"
wrote:You may be able to get
more help here. Whats the problem??
>
> Phillip R Hull STET
> phil245@xxxxxxxxxxxxx
> FAX 517--569-3075
> Professional Technicians only
> ----- Original Message -----
> From: "Paul"
> To:
> Sent: Tuesday, December 30, 2003 4:57 PM
> Subject: [TechAssist] Question Thomson technical help.
>
>
> > Have any of you used Thomson technical assistance recently? If so how
> would you rate it? Both AFS and non AFS. I have not called them in a
number
> of years,but the last time as I recall it was rather expensive and they
> didn't help with my problem. Paul
> >
> > Paul ,B
> Central TV&Video
> Grover Beach Ca.
> >
> >
>
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> Paul ,B
Central TV&Video
Grover Beach Ca.
>
>
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Paul ,B
Central TV&Video
Grover Beach Ca.
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