CTC 187 strange volume problem
klem kedidelhopper
volume gradually decreases by itself. I was thinking possibly tact
switches but someone else said that it could be a bad eprom. I was
wondering how one might go about isolating this problem?.
I ran this set for a few days and never noticed a problem with the
sound. I was about to call the guy and have him pick it up and suggest
that perhaps the problem was the cable box when I mistakenly went to
bed one night and left it running in the shop. I woke up the next
morning and realizing that the set was on the first thing I noticed
was that there was no sound coming from the shop. I took a look at the
screen and noticed that every 2 or 3 seconds a volume bar would appear
then disappear as thouh the set was being addressed by either the
front panel tact switch or the remote. The volume indicator would show
the sound to be all the way down each time it would appear as it
indeed was. I tried raising the sound up and although the volume bar
appeared and it did increment up it then afterwards immediatly slowly
incremented down by itself.agsin. I haven't opened this thing yet as I
really wanted to confirm his complaint first. Now that I have and
considering what I've observed, does anyone think that the presence of
the volume bar points to a leaky tact switch? Or could the volume bar
and subsequent function activation be initiated by either a bad T chip
or the processor? .
I guess what I'm wondering is if there is any way that the set could
produce a volume bar without the appropriate infrafed signal coming
through the IR receiver or the chip being addressed directly through
the tact switch? Thanks, Lenny
Meat Plow
Unplug the IR receiver and tact switches ( P/J3001)then retest.
--
Live Fast, Die Young and Leave a Pretty Corpse
klem kedidelhopper
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The tact switches seem to be the general consensus here. I really
appreciate the advice. I have a theory on this problem that I would
like to share. I also service commercial apartment house intercom
systems. The apartment stations used in these systems are simply a 45
ohm speaker and three NO pushbutton switches. The switches are:
"talk", "listen" and "door", (The last of which buzzes the front door
solenoid to let people into the building.
Quite often I'm called out to one of these buildings to troubleshoot
what seems like an impossibla weird problem. It may be that the lobby
door solenoid is buzzing constantly, or perhaps the lobby speaker is
crackling, or sometimes you find that you can listen to someones
apartment constantly through the lobby speaker. Every apartment
station sits on a three wire common trunk line so natually the
occurance of any of these problems disables the entire building.
Many of these apartment stations use a form of a tact switch that just
fails at tmes for no reason. Disconnecting that problem apartment
station from the common trunk line in every case restores proper
intercom function through the building. One particular 24 unit complex
I service has four trunk wires in parallel each serving 6
apartments.Once I've isolated the problem down to a particular trunk
line or group of six I will ask the building manager who the smokers
are in those six apartments. Nine times ot of ten the problem switches
are in the station that has been exposed to heavy doses of tar and
nicotine.
My theory is that the smoke residue or the dust that clings to it must
be conductive and therefore provides a high resistace short across the
open switch. This has happened on more than one occaision so I don't
believe that it is coincidence.
As it happens this TV customer is a heavy smoker too. The chassis
had a thick "blanket" of
sticky dust that I had to blow off with my vacuum cleaner before I
could even put this on my bench.
For fifteen years this guy has been blowing smoke at this set. I
think that it finally suffocated. Just
a theory. What do you think? Lenny
hr(bob) hofmann@att.net
wrote:
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You proabaly couldn't win this case in a court of law, but it sure
seems very likely that you are on the right track.
Meat Plow
Since the tact switches are N.O. you can easily prove them to be
contaminated. They plug directly into the MPU as does the IR-RX.
I have been on house calls of heavy smokers. Everything is covered with
tar. I too smoke, maybe 6 or 7 cigs a day. I own two Hunter QuietFlo
30736 tower air purifiers that are on here 24/7. Really keeps the dust
down and no sign of any tar. Your theory is solid. And easy to confirm.
klem kedidelhopper
I found a thick film of yellow,brownish sticky residue on the board.
Dust sticking on the HV wires and yoke looked like feathers. I have to
move these sets out of the shop and blow them out with the vacuum
before I can even work on them. I replaced all the switches on this
one and cleaned the control board with 99% isopropyl . The problem
seems to have abated. Qtips were completely brown, sadly, probably the
same color as his lungs. Thanks for listening. Lenny