CRT TV constantly switching itself off - willing to fix myself, but need advice.

Access

Hi, This is a long shot but i said i would at least try.

I have a 32 inch Philips CRT tv in the kids playroom that i had previously got fixed about 2 years ago as it was switching off randomly at the time.

It cost €70 to fix that time (cap replaced) and the tv repair guy who did it told me it would probably do the same again in the future... 2 years on and the same problem has occurred.

I would like to make this tv last a while longer, as we have a child with special needs and replacing the large CRT with a easy to flip over, costly and easily damaged LCD is just not practical at the moment.

I have very good soldering/PCB repair abilities so i would like to take a go at least in replacing the damaged cap to get at least another year out of it.

Does anyone have any experience in replacing/repairing old philips CRT tvs... and could they point me in the direction of the possible part(s) i might need to replace.

The model is Philips 32PW5407



Thanks for any help on this one.

ZENER

Does it turn off completely or go to standby mode ? I would expect a capacitor to last more than 2 years to be honest, I'm guessing the set is a few years old and it lasted longer than 2 years from new before it gave problems ? How long after power-up does it turn off ?

The problem with a set like this is that the capacitors get a lot of use and it's quite probable that it's a different component this time. Some cap problems are observable - swelling, leakage - but most of the time you can't see it. If it was me repairing that set I would have replaced all the caps in the power supply section (total cost of components = < 5 euro) assuming they had all been there the same amount of time and all subject to the same stresses.

A circuit diagram would be essential usually but you could try replacing the caps in the power supply on the secondary side of the transformer. Try sourcing higher temperature rated devices than the original. It's usual for the originals to be rated at 85 degrees so replace them with 105 degree parts to be sure.

Ken

ZENER

PLEASE READ SAFETY MESSAGES ON PAGE 5 OF THIS MANUAL BEFORE PROGRESSING !

There are extremely dangerous voltages present in this TV (in excess of 20,000 volts !!!!) These voltages can and often do kill !

How competent are you dealing with high voltages and using a multimeter by the way ? If you have any doubts then don't do it !


There's a Schematic for this chassis here. Start by measuring the output voltages from the Power Supply (page 21) @ P4, P5 & P6 during normal operation then during the fault condition. Report your findings.

Ken

Access

ZENER wrote: »

Does it turn off completely or go to standby mode ? I would expect a capacitor to last more than 2 years to be honest, I'm guessing the set is a few years old and it lasted longer than 2 years from new before it gave problems ? How long after power-up does it turn off ?

It was bought from new... so its about 5/6 years old... and its the exact same problem now as the last time when i had it repaired.

Over the past 3 month approx... I would turn it on via remote from standby and within a few seconds (5 to 10 secs) and it would go off back to standby mode... pressing on again would normally work and away it goes... but like last time... the past week or two... i would have to repeat these steps 3 or 4 times and now its endless repeating of this.

On just checking there tonight... powered on the tv, it went off into standby after 5 seconds... but did manage to stay on after that for a good 15 minutes surprisingly.

Am competent with mains voltage and wiring and i do possess a couple of multimeters but have to say TVs are one bit of equipment i have not attempted to repair.

Thanks for the Schematic... will get at that Thursday morn and report back in the evening.

icjzfmq7ewon1t

I have a Sanyo tv that behaves in a similar fashion. My solution is to never put the tv in standby with the remote instead I only use the power button on the set itself to turn it on and off. I'm not a technician so dont know if its the same problem but it works for me.

Access

On visual (powered off) inspection there does not seem to be any damaged components internally... no leaking/bulging caps but i am shocked by the amount of slight charring on the inside of the casing and around the area of one of the transformers.

The amount of dust coating on the pcb and tube is mad... never seen it that bad on any computer or pcb case!

I think my senses have kicked in here... not too excited in powering this up with the case off as even a quick call this morning to my old man (retired electrician by trade) put me off totally by informing me that i would be mad in the head to even attempt checking multimeter readings with the unit powered up without previous tv repair experience.

Think this has come end of life now... I think i will have to confer with my missus and bite the bullet and wall mount an lcd in the kids playroom.

Thanks for the help on this zener.

ZENER

Probably for the best. CRTs can bite !! Heat-sinks can be at mains voltage making getting a proper 0V or ground connection a bit tricky.

One suggestion before you bin though. Unplug it from the mains and the antenna and leave it for a few hours to allow the CRT to discharge. Get hold of some compressed air and blow out as much of the dust and fluff as you can. Avoid contact with the cap on the CRT (the red lead). DO NOT USE A HOOVER !!!

It's a long shot but it's possible the dust is conducting and possible causing a circuit where one shouldn't be, cleaning it out just might help !

Ken