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TOUGH DOG: RCA TV model 27V412T, chassis M134C turns off, then on by itself

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 >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 > > Before you type your password, credit card number, etc., > be sure there is no active keystroke logger (spyware) in your PC.
Reply to
Brad
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Yes. Set would turn itself on/off at random, sometimes the front panel controls would work, other times they wouldnt, erratic operation using the remote. Some one had gotten a bit wild with the Windex, which had run down the screen and dripped on the control panel and switches. Replaced the control panel with one out of a junker, not a bit more trouble out of the set, no customer return. HTH

Reply to
Deke

micro bad

Reply to
b

Hi,

I removed the "Power" button switch from the front panel circuit board. Note: I had checked the switch for leakage using a capacitor tester and 50V, but there is no "leakage". There is no sign of anything out of the ordinary on this very clean pcb. There is no residue from a spill.

Since I removed the "power" button switch, the problem went away, but for how long? I will post an "UPDATE" a couple weeks from now if the problem doesn't come back. If the problem does come back, I will post another reply to this thread.

Brad

Reply to
Brad

Hi,

The problem is back after around 4 days. It started when I turned on the TV, a moment later the TV turned off. Then it turned on by itself, then off, etc. I had to pull the plug.

Thanks in advance, Brad

Reply to
Brad

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

Reply to
Brad

Hi, It looks like the problem is fixed (see below for details).

This is the first time I have encountered a button switch/s that tested good (no "leakage" at 50V test), but turned out to have intermittent "leakage".

Thanks to everyone who offered their help, Brad

Reply to
Brad

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