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Old 05-15-2019, 11:14 AM   #1557
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: 2,853
Default Re: the gutless, bloated, and fried power supply hall of shame

The generic-junk "Y" caps were pretty obvious to me too. What are they, 1000pF or 470pF?

There's no way in Hades that thing could ever sustain 350W for more than milliseconds. That said, the things that limit it to somewhere around 200W are probably the input rectifiers, the MJE13007 clone switching transistors, and that less than substantial output inductor. The main transformer might also by wimpy, and those output wires remind me of Clara Peller's famous line. The fan is a POS, and the common mode inductor looks pretty minimal.

The heatsinks seem to have a bit of substance - maybe OK to 250W. The switching transistors, TL494 clone PWM and -26 material output inductor core mean the switch frequency is probably in the 20-30 KHz range. The +5V and +3.3V output rectifiers are downright beefy. OTOH, the +12V rectifier seems to be rated for 12A while the PSU rates the 12V output at 14A.

Multiple swollen output caps, and the rest are probably in poor condition. The input caps are probably true 560uF parts with 680uF wrappers. Assuming they aren't in the process of croaking.

Replace all the crappy parts - the bad, the missing, and the wimpy - and it might be an OK 250W PSU
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PeteS in CA

Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.

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