Philips 32PS55 S3231 Powers up, then shuts off 20 seconds later.
 

A friend of mine has a Philips 32PS55 S3231 TV made in October 2002. It powers up, gets a nice picture on the screen, then shuts itself off. What could cause this, and how do I fix it?

Does it use an LO1.1U chassis? If so, there is a kit from www.matelectronics.com that contains a HOT, two electrolytic caps, and two smaller transistors. Usually, the caps fail and will eventually take out the HOT. These parts are in the horizontal driver circuit.

The HOT's fine. It gets a nice picture, for the few seconds it's on.

I also remember a cap failure in a circa 2002 20" Philips that caused your problem. It was either a 47 uf or 100 uf, 200V cap in the B+ line.

All right. I'll start cap hunting tomorrow.

I don't think it's a bad cap this time.

I've tested all 160 volt and higher caps, and they've passed. Also, the caps are Nichicon caps, which I know to be a reputable brand.

Also, the TV's been doing this for at least 3 years, according to the owner. It's been sitting around since then and now he finally wants it fixed.

Something in the b+ gets overloaded? When the set turns off after the first initial 20 seconds, then power it back on. Does it take another 20 seconds to shut off again or is it much faster the 2nd or 3rd time around?

Call me dumb but I would resolder all heat syncs on the PCB. I have found this a time or two. Something is overheating shutting down the PS

I tried powering it up, letting it shut off, then powering it back up again. There was no decrease in the time it took to shut off.

I just had another thought. I've never experienced this on a Philips; but, I've heard that on newer Philips sets that the master G2 control (on flyback) must be set correctly or the TV will shutdown. I have experienced this on a newer RCA that I replaced the flyback in. It was a trial and error process; but, I finally got it adjusted where the set would stay on.

The VG2 control can be adjusted without having to take the case off. I doubt that's the issue.

On a hunch from a post on another forum, I started looking at the resistors on the CRT neck board. I found a 25-26 ohm resistor that reads only 1 to 4 ohms. When I can, I'll replace it and see what that accomplishes.

check all low voltage electrolytics in the PSU stage, especially the smoothing capacitors on the B+ rails, they may fail and overload the PSU or cause excessive switching ripple/insufficent voltage to reach the signal/logic circuits.

Are you testing that resistor with a leg pulled from the board?
I second that g2 control, seen it too, and especially since it's accessable from the back of the set, someone could have cranked it up. Sometimes it doesn't take much to run the PS into shutdown.

Removed it completely from the board and tested it three seperate times.


Also, if the VG2 control could cause this TV to shut down, then why is it accessable without even having to remove the back cover? Makes no sense if it could shut the TV down. Also, this TV's owner is very unlikely to even know what a VG control is, much less poke in a screwdriver to adjust it.

That's a good question; but, I know they can get turned, even if the owner does not realize it. I fixed a 36" RCA for someone I know and showed them how well it played before they left with it. They loaded it up, took it home, and called me complaining that the screen was almost black. I went over there the next day and both the focus and G2 controls were turned down. They swore that they didn't touch those controls and they had no idea how they got turned down. On this set, both controls could be turned with the fingers without removing the back.

It could also be that the CRT has gotten slightly weak, throwing off the original G2 adjustment.

""It could also be that the CRT has gotten slightly weak, throwing off the original G2 adjustment.""
i see it a lot in the philips chassis. their crt,s were not much better than zeniths. and the g2 setting will shut down the set. to low or to high and the damn thing will shut down. steve

I'm going to replace the bad resistor I found on the CRT neck board first. If that does nothing, I'll fiddle with the G2 control.

I really don't think it's the G2 control though, as the picture looks fine, and the CRT is at full brightness in under 10 seconds. Really, the TV only stays on for closer to 15 seconds, now that I've counted it.

Eh, that "resistor" on the CRT neck board is actually a coil that just happens to look EXACTLY LIKE A RESISTOR! I only found this out after putting in a 22 ohm resistor and getting no picture on the screen... and the TV still shut off after 15 seconds or so.

I only found out it was a coil by looking at the tiny diagran on the PC board... Good going Philips... use parts that look exactly like other parts, and don't bother to label them properly. That ***REALLY*** makes me want to buy stuff from you!

Anyway, after that I started checking all the caps near the power supply, HOT, large IC, and power button. All of them tested fine. These are Nichicon caps. I've never seen a failed Nichicon cap, especally in a TV that's only seen 3 years of use.

I'm at a dead end. Anybody have a SAMS for it, or a definite answer as to why this damn thing shuts off by itself?

When you have a raster on the screen, do you see a flicker in the vertical deflection? Or does there seem to be a stretched width in the horiz?

Nope. The raster is in apple pie working order. The picture looks fine, for the five seconds that it's on.

if i were you i would not touch that g2 control untill you have checked almost every part in the set and found them good..

I haven't touched the G2 control yet.

Lets see: I've tested all caps in the power supply, the HOT's obviously fine, as the TV has a fine raster for the few seconds that it's on. Nothing is overheating. It doesn't even have the chance to get warm.

I thought a resistor on the CRT neck board was bad, but it turned out to be a coil that happened to look exactly like a 4 band resistor...

There is nothing burnt, or any caps with shrunken labels. This chassis actually has relatively few caps, and as far as I can see, they're all Nichicon caps. Every cap I've tested reads fine.

I'm stumped.

I checked the Sams Photofact online index and nothing turns up on that model number. I think a service manual is in order for this set. Try www.tritronics.com and see if one is available. The only other thing I can suggest is get a service manual from Philips and check all the power supply voltages. It could be possible that the B+ is high and triggering a shutdown circuit. Many of these newer TV's have so much "fault detection" circuitry that the older sets did not have. On the older sets, whatever was wrong just shorted and smoked something, making it real easy to find the trouble.

Did you try some resoldering of heat syncs around the board esp the HO?

Um... That website sells dog training equipment...

If I have to buy a service manual, I'm gonna just tell my friend to shitcan the TV.

Unless some other thing to try comes up, I'll fiddle with the G2 control tomorrow.

freakafter8: The heatsinks are fine. The transistors don't even have the chance to get warm. The TV ALWAYS shuts down at the same time. This is not heat related.

Oops! Sorry! I meant www.tritronicsinc.com. See what happens when I type fast while not thinking about what I'm doing!

what i am trying to tell you is that the g2 has to be dead on or the set will shut down. a little to low or a little to high will cause that set to shutdown. steve

Okay, I adjusted the VG2 control, just a little bit, and...

The fucker's staying on.

Okay, from a design standpoint: THIS MAKES NO FUCKING SENSE!! From a planned obsolescence standpoint, sadly it makes perfect sense...

I hate Philips now. NEVER will I buy a TV from them!

Yes, it makes perfect sense for them to design something like that from an obselescence standpoint. It's just their way of insuring that the set will be rendered non-operational in a few years. I would not buy a current Philips product, either. I was not impressed with the quality of the few post 2000 model Philips TV's that I've seen. I did come close to buying a Philips CD recorder. That is until I read all the negative reviews on the thing. The NAP (Magnavox, Philco, Sylvania) TV's of the '80's and '90's were pretty good quality. I still see many '90's era Philips-Magnavox sets that only need minor repairs to get them going again.

I'm glad this isn't my TV. I have never seen a TV shut down due to an out of adjustment VG2. I didn't even think a TV could detect something like this.

Is there anyway to disable this "protection"?

hate to say but i told you so. i dont like anything philips or panasonic makes. steve

Is there anyway to disable this "protection"? not that i know of. the crt is starting to get weak. their crt,s were only a little better than the zenith crt,s

It's just such a stupid reason for a TV to shut down. I mean, WTF is next? A TV with a timer in it that disables the power supply one day after the warrenty expires?

Hey sounds like something Funai would impliment into there next design...
Shhhhh.... There listening!
lol

Glad to see it's working for you now..

How did the picture look after you turn down the G2?