TOUGH DOG: RCA TV model 27V412T, chassis M134C turns off, then on by itself
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 Before you type your password, credit card number, etc., be sure there is no active keystroke logger (spyware) in your PC. |
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