Hi,

I finally found something that may be the cause of this problem. I will
report back in a week or so after I confirm it.

This was the first test I performed on this TV, which "past the test".
I used a capacitor tester's "leak" test (very sensitive) set at 50V and
checked all the button switches. Absolutely no sign of "leakage".
I won't tell you all the other things I did. Sometimes it pays to re-test.

This time, when the TV started it's off/on "ritual" again, I unplugged the
TV and I performed another "leak" test on the button switches.
Wow!!! now I have a "leak" indication. Imagine, an intermittent "leak"!!!
I opened the circuit trace to all the button switches. Now, I will use the
remote control on this TV for the next week or so to confirm. Please
"stay tuned".
Brad


On Mon, 05 Nov 2007 16:18:35 GMT, in sci.electronics.repair you wrote:

Hi,

PLEASE READ my original post below.

I have a RCA TV model 27V412T, chassis M134C (mfg 01/06) back in my shop,
which I thought I repaired after I replace the remote receiver. The TV worked
fine for a couple days, then it started all over again. I removed the remote
receiver and put a 10K from +5 to the remote's output line, but the TV
still turns on, then off by itself. I checked for leakage on the panel button
switches. Also I found out, before I removed the remote receiver, the TV
would not respond to remote commands, and the scope showed a good
output signal from the remote receiver. Note: The TV did respond to remote
commands when I first started working on it. I checked the +5V and scoped it
for noise.

I found info on the Web about a setting in the service menu that can cause
this problem, via "7", OPTM2 should be at "00", but this setting is correct
("00").

Did you have a similar problem with this or similar a model TV?

Thanks in advance, Brad

On Thu, 25 Oct 2007 14:25:39 GMT, in sci.electronics.repair you wrote:

Hi,

I have a RCA TV model 27V412T, chassis M134C (mfg 01/06) in my shop
that seems to have a mind of it's own. My customer said this problem got
worse over time (a few weeks). I have Sams Photofact 5234.

The TV will play for a short time, then turn off, a short time later, it
turns back on, then again it goes off, etc. I checked all solder joints
(AOK).

HV is 28KV, reg B+ is 130V "run", and 10V in standby.. While the TV
played, flexing the circuit board (removed from it's holder), tapping the
circuit board, using a hot air gun on parts, had no effect.

I checked electroylitics in primary side of SMPS and reg. B+ (AOK).
I checked voltages on secondary side of SMPS and found a schematic
error for 24V source. I found 24V present at emitter of Q205 used as a
"switch" (one of several) which indicates the 24V source is normal.

Did anyone encounter a similar problem?

Thanks in advance, Brad

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