Yamaha CS-60 part 4: Power supply capacitor replacement

The power supply only has 9 capacitors. They are big for the most part and their replacement should have been easy. It was not. The capacitors are folded inside the power supply, so it has to come apart. Once I got it apart I found that four of the caps (2x 100uf & 2x 3300uf) are glued to the board. On top of this the power supply is heavy and awkward to move around while doing the work. I could have desoldered the 25 or so wires, but that didn’t seem like much fun. Anyway, this is how it went.

I didn’t get a picture form above before I removed it. I’ll add one when it’s complete at the end. This is the view from below. Those two upper screws mounting the heat sink have to be removed so the heat sink comes free.
The four corner screws seen here hold the standoffs that the PCBA mounts to. You don’t want to remove these. Better to remove the four screws mounting the PCBA to the standoffs from the other side. Replacing the white thermal grease seen here is good practice during maintenance.
You have to disconnect those two white connectors seen here in the upper right. You can kind of see how the PCBA is mounted to the closer heat sink and sandwiches between the heat sink and hook ups / fuse block.
Here is a good view of the standoffs on the heat sink the PCBA mounts to. Also a good view of how many wires you’d have to desolder to “do it right”.
I took this after some work. The two 3300uf caps were glued down to the PCBA and they had a soldered pin to secure them to the PCBA. I used solder wick to remove the old solder. If you try and wiggle the caps loose, without the solder completely removed you will lift and damage the traces. Not the end of the world, but being careless and making extra work for yourself is never a good idea. Not much fun to replace these caps, but as you can see here, it is possible.
You want to avoid banging into the legs of the transistors on this board while trying to cut the glue…Note negative stripes on the smaller caps. There are no discolored resistors anywhere on this power supply. A good sign that it has been healthy.
Those 4558 dual op amps probably should be replaced, but I am not doing ICs until after I finish replacing capacitors and make sure everything works. Those trim pots are used to set up your voltages. I will document that in the next post or two.

I have two 1000uf caps still to replace on this board. I have some cheap Xicon caps on hand, but want to use at least decent Nichicon caps. Mouser order should be here today, so I will knock them out and do the calibration. Once that is done I’ll make sure the CS60 still works then replace the caps on the PRA board, followed by the voice boards.

Emanuel posted this picture to a gearspace thread a while back. Might help someone someday.

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