Re: CTC169 Dead Set HELP!!!

O.k. - (I hope) you may have given me a big clue when you said that the run supplies are not "getting on their feet". I will assume for now that the standby's are NOT dropping significantly when you attempt power on, which will lead me to what I am about to suggest...

(Once again, I type from home in the evening, and have no schematic or old boards in front of me, but here goes...)

On the underside of the board, on the secondary side of the switching transformer to the left of your rectifiers, such as CR4118, etc. (viewed from bottom)look for another, larger filter capacitor that leaks. It will wick down to the UNDERSIDE (foil) of the board, and have the green coating blistered, or lifted in places all over several fine PC traces that if you scrape and clean them (the ones with black-looking blisters and bubbles) you will find they are quite oxidized, and black. I think you may find at least one of these eaten completely through, and causing lack of Run B+, therefore no supply from which to generate horiz. drive pulses... I have been also seeing this more and more often lately, too as these sets get some age on them... I hope this gets it for ya, as I am running out of ideas, and you sound like you know these chassis pretty well, too. Oh, yeah, and replace that cap when you are done patching trace(s). It should be pretty evident on close inspection which one is a leaker - and it will smell like fish when you heat the leads! I wish I has a cap' number for you but as I said, I type from home (and I pretty much I just know which one physically to look for from memory when one is in front of me...)

"Marc" <marcfb@xxxxxxxxxxx> wrote in message news:dYydnfGiQPwcEi3VnZ2dnUVZ_jSdnZ2d@xxxxxxxxxxxxxx
Haywire,

I did as you suggested and removed the osc and the two caps that had residue
under them. I cleaned the board with alcohol and a q-tip. The problem
remains.
I checked out the power supply again. I have a constant and stable 143v
along with my correct standby voltages. When I try to turn the unit on, I
see pin 28 of the U31001 trying to switch the supply to RUN, but it does
not. I also monitored the horizontal signal at pin 23? and I can see it is
trying also. The PWM signals are not present on the regulator IC, but I
still have my B+? It appears that the PWM might be missing since the unit
will not come out of standby. The main problem is that I dont have my run
voltages, especially 9v. Knowing that the last tme the set worked, I had
alot of horizontal lines in the pic, makes me believe the issue is in the
horizontal circuit. I just dont have sufficient circuit desc or
troubleshooting info to systematically check all the possible places.
Anxious to solve this. It has become my off and on project now for 2 months!
Hoping you have some additional ideas - or anyone else for that matter.
thanks, Marc
"Haywire1" <haywire1@xxxxxxxxx> wrote in message
news:48acd7b7$0$24564$470ef3ce@xxxxxxxxxxxxxx
Hmmm, I'll have to look at the schematic to be sure, but there are two
identical in value - my memory may have failed me on the values (150uf,
maybe?) one filters Defl B+ (To the T-chip) and the other filters a
seperate
B+ pin on the same IC. Both can make a mess on the board - it is the
conductivity of the leaked electrolyte that causes the problems, and can
usually be seen by a wet spot eminating from around the culprit
capacitor(s). Most of the ones I have seen leaking had dark brown heat
shrink on their case, but since RCA used different suppliers of discrete
components during manufacturing, it is possible they may be dark blue, or
whatever... Try removing the oscillator by desoldering, and clean up the
board. It is not even necessary to replace the caps for a test run, but I
would after deciding whether this is your prob. or not - for the longevity
of the repair. Another tell-tale sign that this may be your problem, is
that it may smell like rotten fish during the desoldering process (of the
oscillator, or the suspect cap's) due to the boiling/burning off of the
electrolyte from the heat of your soldering iron. If that happens, you're
probably on the right track, and it may be necessary to replace that
little
blue oscillator if it cannot be adequately cleaned, or if the acid-based
electrolyte has wicked up inside the "unsealed case".

Also, my scratch-and-sniff approach may be off-target. Do you have any
horizontal drive pulses coming out ot the T-chip?

"Marc" <marcfb@xxxxxxxxxxx> wrote in message
news:ucydnRKaXNLFXjHVnZ2dnUVZ_jOdnZ2d@xxxxxxxxxxxxxx
> Haywire,
>
> I looked all over the board and even in the parts list (sam's
photofacts)
> and there are no 330ufd caps on my chassis. I do see the small blue
> oscilator. There is some residue around the the end of the chip and
there
> are 2 caps, but they are not brown and nowhere near 330's. Any chance
you
> can share the part symbols for the caps?
>
> thanks,
> Marc
> "Haywire1" <haywire1@xxxxxxxxx> wrote in message
> news:48ab5c9b$0$24578$470ef3ce@xxxxxxxxxxxxxx
>> Sounds like your power supplies are working and you have no horiz
> drive.
>> Look for two brown 330uF capacitors leaking electrolyte onto the board
in
>> the vicinity of the T-chip. It will ooze under the Horiz. oscillator
> (Blue
>> plastic case, near T-chip) and stop horizontal drive. As these sets
get
>> older, this is becoming a VERY common problem. Replace the caps (to
stop
>> them from leaking electrolyte), clean up the board (with the >> oscillator
>> removed) - you can try to reinstall the oscillator, but I have had >> some
> that
>> actually soaked it up inside, and it was necessary to replace. If the
>> Horiz. output was shorted, the power supply would not be able to
develop
>> +143V...
>>
>>
>> "Marc" <marcfb@xxxxxxxxxxx> wrote in message
>> news:2f6dnTbNo55USDXVnZ2dnUVZ_s_inZ2d@xxxxxxxxxxxxxx
>> >I sure could use some assistance repairing the subject TV. I have
> replaced
>> > the usual suspect caps, reg IC and the chopper transistor. I have
143v
> of
>> > B+
>> > and the standby 5v and 15v (13.5v) supplys are working. I also
replaced
>> > the
>> > flyback. Before the set failed there was a lot of horizontal lines
(in
> the
>> > old days, it would almost be called tearing). the set would shut >> > off,
> then
>> > try 3 times and quit. Now it wont turn on at all.
>> > Marc
>> >
>> >
>>
>
>




.

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