XVI - Loud buzzing sound from PSU

[Caseh]

Have just fully recapped the PSU for a XVI along with replacing a fried ZD31 diode and R23 resistor. Everything on the board checks out, the system sits happily in soft-power mode and switches between 10Mhz/16Mhz successfully. When powered up, the fan spins up then shortly after there is an extremely loud buzzing/humming sound coming from the PSU.

The system seems to run fine, reaches the insert disk prompt but i'm apprehensive about leaving it on for any longer than that until I know what the sound is. Any ideas?

[kamiboy]

I had a similar problem with an ACE PSU. Turned out the buzzing was due to noise in the generated DC voltages due to the filter caps being of too low a capacitance. I had replaced them with one of similar capacitance, but I noticed later revisions of the PSU had increased the capacitance significantly.

This could also be due to cold solder joint on one of those two filter caps. On the Ace they are around 3-5000 uF 10-16V.

[Caseh]

I think I know the ones you're talking about, the original caps were 10v - 5600 but the replacments I bought are 10v - 6800. Bought a full sh4 cap kit from Japan so figured they would be fine but it's a good starting point.

[Caseh]

All fixed! Had a friend in work have a quick look over the schematics for the different PSUs and drew the conclusion that the resistor used was the wrong rating. Replaced R23 with the correct resistor and the XVI is now running without making any excessive noise!

[costa]

Would be nice if you let us know what resistance you have used to replace R23.

I had similar issues (buzzing), turns out my solution was to use lots of silicone to help fixing the caps tight and stopping vibrations.

All fixed! Had a friend in work have a quick look over the schematics for the different PSUs and drew the conclusion that the resistor used was the wrong rating. Replaced R23 with the correct resistor and the XVI is now running without making any excessive noise!

[Caseh]

I'd used the spec for the PSU in the Super which I assumed to be the same as the XVI. So I had initially used a 2.7k ohm resistor, when replaced with a 30 ohm resistor it resolved the issue.

Although with that said, it has now developed another issue.   When switched on, it bypasses the soft-power stage and sounds as though it's powered up but when the power button on the front is pressed a audible clicking sound can be heard from the internal speaker. It doesn't power up, instead the power light strobes/flickers along with the FDD lights and it can be switched between 10/16MHz which should only really be possible when in a soft-powered state.

It's all fun and games with these systems eh. I have a Super as well which is in a good working state so this is just something i'm tinkering with when I have time.

[Caseh]

Just adding this image as well, took a pic before the recap and tagged the caps for a quick reference. Unlikely to help anyone really but may as well add it.