Philips PM3055 won't power up / buzzing sound

[VirusCrazy]

Hi,

I've got an old Philips PM3055 scope that I've used a few month. Recently, as I had to move, I left it unused for around 3-4 month and now, it won't powers up. It makes a buzzing sound and this sound seems to come from the main power supply unit. It already did that before but after a few day of non-use and it was working after.

Now, it will only power if I disconnect some boards of the scope.

Do you know where does this come from ? Capacitors ? Tranformer ? ??

Any help would be greatfull.

Regards, Jerome

[Mr Walker]

Usually transformers make buzzing sound- but really, anything in your scope or power supply could be to blame- if you are not capable of diagnosing/fixing faults safely, may I suggest that you find a capable repairer?.

[Guest]

I'm capable of diagnosing faults as I do that in tvs and other electrical equipment. I was just wondering if someone had this fault as it is a switching power supply and there is a lot of capacitors in it. I don't want to spend 1 month searching for an potential common fault on this scope.

If I don't have any replies which can help me, then I will start to diagnose more deeply.

Regards, Jerome

[torbjorn]

In older Philips equipment, it is very common that the blue axial electrolytic capacitors get bad. Usually they fail short circuit but when subjected to higher temperatures they may also get high losses and low capacitance.
The older ones with a beige or white rubber plug at the positive terminal seem to be worse than the newer ones with black rubber.

[Guest]

Hi,

Thanks for the information. I'm gonna list all the capacitors and exchange them. I think it's just that they are too old and they have done their time. I will let you know.

Thanks again, Jerome