Electronics

Chris F. · Guest

I hate servicing projection sets, but agreed to this one simply because
business is so slow these days. Right away it's obvious I will need some
help:
When I first tried the set, pushing power causes the set to cycle on and off
very rapidly (for as long as power is held down). I went through the power
supply and tried replacing some caps; now, pushing power starts the set for
a half second and it shuts right down - and will not try to start again
until the set is unplugged for a minute. Testing has ruled out HV shutdown.
The first thing I intend to replace is the EEPROM. While I wait for that
to be ordered, can you give me any other advice? The customer said the set
would also go to a black-and-white picture once in a while, and turning it
off for a few minutes would correct the problem (at least for a few more
minutes). So I suspect there may be other problems waiting to be found, once
the set is brought back to running condition. Or is that perhaps a fault of
the EEPROM as well??

James Sweet · Guest

Does the EEPROM commonly fail on these? I don't think I've ever come
across a bad EEPROM in a TV, not to say it doesn't happen, but it
certainly wouldn't be my first suspect unless it's a known issue.

dkuhajda@locl.net · Guest

With the exception of the tuner ground causing failure of the eeprom
data on the direct view ctc177 series, I have never seen an eeprom
failure in an RPTV set.

There is little real technical information in the OP to garner any kind
of help.
It might be best for the OP to post information like a trained,
equipped, and qualified technician would.

Sky · Guest

Unhook the high voltage splitter input from the flyback, & if the unit comes
on with filiaments, you have it. If this fails to get it going, the flyback
may be
bad, especially if nothing else is bad. The red wire next to the flyback can
also make it look like the flyback itself is bad. Look for CRT coolant leaks
....many problems with these with leaks, & a lot more. Is it "squealing"
while
it's trying to start? You have a short, if so. Check the horizontal output,
pincushion correction circuit, & convergence power supply. Hope this
helps. EEPROM highly unlikely at fault, unless someone was at the unit,
or if the tuner was really bad...solder connections, & left to long. Sky.

Chris F. · Guest

I neglected to mention the chassis # - it is a CTC-169PT
No evidence of coolant leakes at all, and I've tried to power it with the
yokes & flyback lead disconnected. As I said before, I ruled out HV shutdown
by disconnecting that lead to the TA8680 IC.
I've replaced many bad EEPROMS on the CTC-175 series....
One other thing worth noting; with a VOM connected across the B+ supply, I
noticed something odd; when the set is plugged in, instead of going directly
to 150 volts or so, it goes to about 100 and slowly ramps up to 150 within
3 - 5 seconds. Maybe this is normal, I'm not sure.

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