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Philips 19PFL3403D/F7E: Backlights turn themselves on

I was given a Philips 19PFL3403D/F7E TV because of several problems. The original owner had had two of these. THe original unit didn't respond to the remote, and would turn itself on and off. She sent it back under warranty and was given a refurbished unit. It had the same problems so she gave it to me. Then she found an old 19" CRT set and is using that with her AT&T U-Verse box. :)

I hooked the set up and turned it on. Programmed itself nicely, looked okay. I turned it off and left it for the night. In the middle of the night I saw a glow coming from the room where the set was. The backlights were on but there was no pic or sound. The set wouldn't respond to the power switch. Unplugging the set and waiting 15 minutes or so allowed it to work normally until the next time.

I tore into the set and find that the caps on the PS board all look and test good. I replaced them with quality caps anyway. I press the power switch and everything comes on, but there's no pic/sound. On a fluke I unplugged the switch assembly and that restored the pic/sound; plugging it back in turned the set off. This was repeatable. I resoldered all connections on the power switch board and now the set goes on and off properly but still has the "set powers up by itself with backlights but no pic/sound" issue.

Could this be a cap related issue on the main board, or perhaps poor solder joints? It seems unlikely that a new set and its refurbished replacement would have the exact same problems.

Reply to
prc1crap
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Maybe you have some sort of signals in the area that trigger the set. Like the garage door opener problems some folks have had that live near Navy bases.

Reply to
hrhofmann

Not being funny - but how about giving the set a tinfoil hat?

Wrap it in foil and se if that stops the backlights powering up.

Reply to
Ian Field

(snip)

The softON-softOFF power control function leaves the PSU energised and the backlight control is simply a logic level switching. A leaky transistor or equal in this area can cause what you describe. I'd be looking more in that area than the tin-foil zone.

Reply to
who where

I appreciate the input--many thanks for taking the time to take a stab at this problem!.

Ibelieve I've found the problem--crappy soldering on the control button assembly PC board (Philips # 715T2911-1, also used on ILO, Magnavox, and other brands). After re-doing the joints on this board the TV no longer turns itself on.

However, I now have another problem...during the solder removal I managed to lose the R016 resistor that goes with the SW016 switch for the Menu button. I took a wild guess as to the value and now have two Volume + buttons. Does anyone have a schematic (or one of these boards) that could tell me the value of that resistor?

Reply to
prc1crap

Wire-out to a pot to bracket the value

Reply to
N_Cook

I hadn't thought of that. Thanks! FWIW, the value was 10K ohm.

Reply to
prc1crap

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