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Old 04-22-2022, 11:50 AM   #3187
PeteS in CA
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Join Date: Aug 2005
City & State: San Jose, CA
My Country: USA, Unsure of Planet
Line Voltage: 120VAC, 60Hz & 115VAC, 400Hz
I'm a: Professional Tech
Posts: 3,398
Default Re: Power supply build quality pictorial. part 2

How often have I posted this: those heatsinks do look reasonably substantial. The main transformer looks reasonable as well. 820uF for the input lytics seems a bit marginal for 500W (more OK for 400W-450W), and I don't love that they are 85C rated. ASSuming they current-share perfectly, those paralleled 12V rectifiers are not good for 28A ... even 16A rectifiers paralleled would be marginal for 28A. In contrast and oddly, the 5V and 3.3V rectifiers are reasonable for the rated current. Another oddity is pairing a -52 material output inductor with a TL494 PWM and bipolar transistor switches (both of which keep the switch frequency low, probably around 25-35 KHz).

But for the under-rated 12V rectifiers, that looks to be a fairly decent PSU crapped up by low quality capacitors. And it did last for 10-16 years ("06" date code on one of the input lytics). Given that vintage, replacing the crap caps on the secondary side with PWs or LXZs should yield a pretty decent 400W-450W that could deliver 500W peak power for more than a femtosecond or two.
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PeteS in CA

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