Another Squealing LC?

[Elfen]

This is an LC I bought as part of a deal because one of the ROMs was dead and would not boot. I recently got a new set of ROMs, put it in, and "BONG!"

It's alive again!

But it is squealing from the speaker, which is a sign of it needing a recapping job. But this LC was recapped, but I am using a PSU from another LC III. This LC III PSU is not recapped, but will be soon as soon as I get some caps. I do have a LC475 PSU that is recapped, and will test that tomorrow for right now I am tired.

I'm suspecting the PSU as the cause the squealing. If so, I got nothing to worry about. I just need to recap a couple of PSUs and close up the machine and call it done.

This is my first Mac Repair since "coming back."

But what else can it be? Any ideas?

 

[johnklos]

Maybe it's just so excited to be running again that it is squealing in delight?

 

[Elfen]

ROTFLMAO!!!!

Laughter is an excellent source of meds.

 

[Elfen]

I cleaned up the board some more though I could have used better chemicals to clean it with. So, I'm suspecting it's the PSU at this point. But I got interesting results.

Squealing is still there but softer in volume. But that depends on how much RAM I put into the LC. And which type I put in (8 chip SIMMs vs. 2 chip SIMMs - both 1MB SIMMs).

With no RAM, the Squealing eventually goes away.

With 8 chip SIMMs, the squealing is there but low in volume.

With 2 chip SIMMs, the squealing is louder.

I need to take apart my IIci (Don't want too!) to test the 4MB SIMMs in the LC and see what is the state of the squealing.

 

[Instow]

This reminds me, I also have a LCIII on the shelf that has a squealing speaker (so far speaker disconnected to save my ears) didn't realise the PSU/RAM has an effect on the problem, but it seems to work OK apart from the sound problem.

Good luck in tracking it down.

 

[Elfen]

Did you clean the board with ammonia, and then acetone/alcohol and replaced the caps?

The PSU is the last thing to recap, but often when you need to recap the board, the PSU needs to be recapped too.

 

[turbo]

But it is squealing from the speaker, which is a sign of it needing a recapping job.

Is this just a high pitched tone?  I have a LC 475 that makes this noise I can only describe as a high pitched tone.  I thought it was the old hard drive, but maybe I need to look again.

 

[bibilit]

Both my pair of LCIII were squealing before the recap job, the noise is gone after the surgery.

Is this just a high pitched tone? 

More like a hissing sound if is related to capacitors.