I have bought already ages ago the new capacitors for the power supply of my 1571 drive, and Commodore 128. Those electrolyte capacitors tend to spill, and fail over time, that's why I decided to prevent damage, and exchange those early. Other than that, my C=128 power supply unit was buzzing loud, and wanted also to investigate that problem too.
Opening up the C128 PS, I found the small bracers on the lower case supporting the transformer broken, so the screws holding it couldn't hold on to anything. This way, the 50Hz freq made the plate on top of it to vibrate, making the annoying sound. First, I experimented with super glue, without success. The glue itself stuck to everything, besides the broke off parts of the stands. I even made the situation worse, by ripping off some of the still somewhat attached parts. However, my second choice, what all the times worked for me so far, worked: the two component epoxy plasticine.
After the curing time, I just needed to carve it to it's final shape, and ready to drive in the screws. On the picture, the two tall, black capacitors are the new ones. Measuring the old ones, I have found them capacitance wide above rating, however the new ones have lower ESR values. After putting all the things together again, and cleaning the wires as well, I have got a reasonable looking, and fully functional C128 PS.
On the 1571, last time I opened it up, I have discovered a suspicious capacitor (the blue one, having sign of excess heat exposure). It was high time to swap it for a new one. Unfortunately, these days the inline version of capacitors are not in fashion anymore, so I could get parallel legged ones with the same ratings. This made me facing a new problem: how will I plant in those new caps., with drilled holes so much stretched apart of each other? Well, fortunately, the PCB traces are wide, and runs next to the other hole as well. Only needed to do is to drill a new hole on the track, next to the other, and plant in the capacitor, lying down. I also exchanged those small ones, which 1uF 63V, and 47uF 16V, with new, surprisingly smaller ones, without problems. Assembling the PSU together again, I have noticed, that before, the mains input was plugged into the 220V line of the transformer. Since in Hungary we have 230V, I have decided to use 240V instead. Also retrofitted those two three legged regulator ICs screwed against the aluminum case, with thermo paste, to help prolong their lifetime.
Turning the PSU on, measured the voltages across different components. 5V output pin: 4.96V, perfect! 12V output pin: 11.98V, perfect! Voltage on the biggest capacitor: 32V. Since it is the puffer capacitor before the 12V regulator, and it is rated 40V, it is considered OK. The new, exchanged capacitor experienced 17.4V! Not good! Since it is rated 16V as it was before the case, with the older, blue cap. Switching the mains input to 220V (as it was the configuration before), made the story even worse, measuring 19.2V on the very same capacitor. This explains, why it showed excess heat wear. I will need to get a higher rated one, any time soon.
Since my 1571 was apart, I took the opportunity to clear the casing thoroughly. It became less yellowish, and gained back a nice grey-brown color. The only surprise I faced: the front label stating "Commodore 1571 Disk Drive" faded as well and didn't stop until it became fully white. I will need to replace it. Other than that, its almost perfect now.
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