The 2012 El-cheapo PSU Roundup

[Pentium]

Awesome. I replaced the diodes with a bridge, replaced the primary caps with real 470uF, recapped most of it, finished adding PI coils and in progress of replacing the secondary heatsink. One thing I'm curious about though, how did this thing manage decent ripple suppression with no inductors and such low capacitance caps? Was it just because the wattage was so low? Just adding the coils will probably reduce the ripple quite a bit I'd imagine.

I will add some more pics soon!

[c_hegge]

Usually, the ones with the real bad ripple only use 1 cap (and often a General purpose cap, not low ESR). 2 caps without the coil will often just do it for 300W or so and under. If I had been able to load it above 300W without killing it, I think the ripple would have been getting close to the limit. We were seeing around a 15mV increase per test, so in test 4 (where it died), it would probably have been around 95mV, and out of spec if it had been able to manage 400W.

[Pentium]

Gotcha. That makes sense. I got the original 16A rectifiers on parallel for the 12V, 30A schottky for the 3.3V and 16A for the 5V. The new heatsink is much better! But there will be none of the heatsink leads grounded to the PCB... I'm waiting for the pic to come through to my email so I can upload it. So far shouldn't cause any issues?

[Pentium]

So it fired up and works! With only one problem....Everything is perfect except the 12V rail is reading 12.92V Is that because of the rectifiers in parallel? They're both the same....Having issues uploading pictures but I will post them

[c_hegge]

Is there any load on it? I had a similar issue when I rebuilt a Key-Mouse PSU a few years ago. It worked fine in a PC, though, with more load on it.

[Pentium]

I figured it had enough load....3GHz Precott P4, 2 DDR2 RAM sticks, CD drive, 2 SATA hard drives. I could try adding a video card

[c_hegge]

Oh, so that was in a PC? It should be lower than that, then, especially if it's a power-hungry P4.

I've just realised, you said you used a 16A rectifier for the 5V. Do you have a 30A schottky you could use there? Reason I ask is because some of these older designs regulate based on the 5V output, so it could be that increasing the 12V capacity has made the voltage inherently higher, and the power supply's regulation isn't compensating because the 5V rail has remained unchanged

[Pentium]

I do have a 30A schottky that I could put in there, I did notice that the 5V rail seemed low but not out of spec at 4.85V. Thank you for that tip, I will try that and see what happens! Here are some pics

IMG_20130510_182749_345.jpg (216.08 KiB) Viewed 20033 times

IMG_20130510_182743_509.jpg (255.67 KiB) Viewed 20033 times

IMG_20130510_171522_468.jpg (232.26 KiB) Viewed 20033 times

[Pentium]

IMG_20130510_182759_586.jpg (206.24 KiB) Viewed 20032 times

[Pentium]

c_hegge....you ROCK! I threw in a 30A shottky for 5V and the 12V dropped down to ~12.3V and the 5V bumped up to 5.04V. Awesome!!! Thank you very much for your help and Insight How does it look?