The Big Ass Cap for input filtering is a Nippon Chemi-Con 400V 220 uF snap in cap. I wouldn't bother with pricing out a replacement...
The PSU has a small step down transformer to rectified DC voltage via a 4A, though unmarked bridge rectifier that is then fed into a TI UCS3843P-controlled DC-to-AC (?) conversion using the big transformer that is fed by a Fairchild FCP11N60F MOSFET. Without a closer look with a scope or meter, I cannot say what the input voltage is for the SO-8 controller, but this is the blow IC that some have pictured and it rated for a 30V input.
This output is rectified by two V30100S schottky diodes, as far as I can tell, in ITO-220AB packages and this goes into 4 filter caps.
The 4 small output filtering caps at the end are 1000 uF, 25V, 105 ˚C, JH CP263 electrolytics. There are two optional replacements I'd trust from mouser:
- EEU-TP1E821 - 820 uF, 25 V, 2K hr, 135 ˚C w/ 1.1 A rated ripple & 0.052 ohm ESR
- UHW1E122MPD - 1200 uF, 25 V, 10K hr, 105 ˚C w/ 2.9 A rated ripple & 0.017 ohm ESR
If both are run at 95 ˚C, their effective lifetime rating will be 32K hrs & 20K hours respectively. However, the higher ESR and lower ripple rating will cause the former to heat more due to the ripple from the steppers and heating elements. As for the latter, you'll get a a beefier filter with 20% more capacitance and up to 11 amps of ripple at 100 kHz; even though the steppers operate at a third of that.
The output voltage is controlled through a TL431A and the 2.47K & 10K 1% resistors. If I'm interpreting the datasheet and the resistors correctly, excluding error tolerances, the output voltage is then programmed for ~12.6V. Toss in a 0.3V drop from the schottky diodes and you have the 12.3V I measured previously.
In addition to the part identification, the MOSFET on the high side of the larger transformer has a max power dissipation of 125W and a max continuous current rating of 11 amps. I'd love to see some additional photos pointing to the failure mode of this PSU, cause it seems like 11 amps in and 10 amps out, assuming it's 12 V AC we're dealing with, is ~91% and that's a tall order. Even with my rudimentary knowledge of this topology, this seems too close to be coincidence.
Toshiba makes a nice MOSFET that I think will work, the TK16E60W,S1VX. I've not compared all of it's specs and a freewheeling diode will probably help keep things in shape for it too. Swap this guy out and the four filter caps.
If you want to tweak the PSU for say, 15 V output, change I'd advise new caps like this one:
- EEU-FR1V821L - 820 uF, 35 V, 10K hr, 105 ˚C w/ 2.47 A rated ripple & 0.018 ohm ESR
The 2.47K resistor needs to be swapped out with a 1.96K resistor. With the schottky's that should leave you at about 14.96 V. All in all, for ~$15 w/ shipping you can beef up this PSU (have it supply more than 10 A?), make it run cooler, and have it upped to a higher voltage if you want.