Is it normal for an A500 power supply to hum?

[da9000]

Hi there,

I have an A500 and the standard (external) power supply makes a humming noise. Now, I didn't notice this before until tonight. I could have been happening before, but I think I would have noticed. Yesterday I replaced the burned 3/4Amp 250V (part 233) fuse inside with a new one, and closed it up. Could this have caused this humming noise?

Just curious what others' experiences are.

[da9000]

Thanks for the answer Moto. I forgot to mention that the humming happens when I turn it on, even when not connected to the A500. So definately not overloaded. The voltages register fine on my volt meter.

I wonder if it could be the "seating" of the transformer when I put everything back together. I'll open it up tomorrow and double check.

Could you explain why the plates on the transformer would vibrate? The transformer seemed fine when I opened it to do the soldering of the new fuse.

Thanks

[da9000]

Hi Karlos,

Thanks for the reply. But can you tell me then what happens and how long before "it's dead" ? Will I be able to move the plates with my fingers or is the movement too small to really notice?

In other words, when should I start looking for a new transformer for my A500 power supply? (also, anyone know what kind of transformer I should be looking for? on the back it says: P/N: 312503-01)

Thanks guys

[da9000]

Ok,

I opened it up again. One of the main caps was a bit loose and it discharged (almost in my face). I soldered it properly. There's still some humming, although a bit less. I can't tell if the transformer is bad or not, but it "seems fine".  I got another A500 power supply, much lighter (has no transformer inside!). It also makes a slight humming noise, but it's REALLY hard to hear (it made me realize which of my ears is more sensitive

Forgot to mention: the humming is DEFINATELY coming from the transformer. Easiest way to test this is: lift it with your hand (wear an insulated glove first!), and if the humming dies down (due to the hand absorbing the vibrations), then that's the cuplrit!

Anyways, we'll see how long thing guy will last I guess..
I just hope it doesn't take my A500 down with it!

Now on to find out why my A500 rev.6a board green screens even though all the custom chips are OK.

[da9000]

Hey Oliver,

thanks for your extended reply. To start off, I didn't try to discharge any of the equipment. I was inspecting it and when I moved one of the capacitors, I saw a discharge, and then noticed the connection was broken. I did test the caps voltage before I worked on them though

Secondly, yes, I'm very careful about the live wires and wearing some protective equipment is recommended.

As for replacing the whole PSU, well yes that's an option, but if I can fix it, I'd rather do that, so I can learn a thing or two. The unexamined live isn't worth living

As for the 2nd power supply, yes, it's a switching power supply, and yes, I noticed the power rating is a bit lower.

Finally, the info on the transformers (rust, whinning/humming when new, etc), was great! I had no idea. Thanks for that in-depth info, it was perfect! If you have any other such tid bits, please tell

If you want to take a stab at this:
How do I determine if the transformer is dying or the whine/hum is normal?
Same for the whole PSU? Maybe it is OK after all. I'd like to learn if there's some easy steps to check the "health" status of said PSU.

Thanks again!

[da9000]

Thanks Oliver, although I wasn't that smart (as far as safety), but I've survived playing with electronics since 8 years old ... so, I've got my angel

Anyways, i'll be more careful with transformers. How can I find the specs for a given transformer?

[da9000]

mr_a500

interesting story  hope mine also runs like so, and doesn't melt down my miggy