repairing power supply

[EWorkshop1708]

drastically changing the output filter caps isnt always a good thing. if you change them to higher values it will change the impedance of the output filter, this in turn can cause instabilities that the control loop isn't designed to stabilise.

I'm willing to take that risk 56,000uf has a lot of peak current and lower impedance.

1. What instabilities do you mean? A typical TL494 PSU has a very fast feedback error amp, and if anything, more capacitance will slow down the rise and fall of the DC output voltage.

2. The worst that could happen if I try this, is that the ATX supply shuts off, or doesn't turn on from inrush current being too high OR it powers up fine and has ultra-smooth 5V rail with lots of peak current! I already tested this on an extra ATX PSU I have, and it works fine.

As far as impedance changing, well good, the lower the better!

I've been planning the mod, but my PSU does not have enough extra room inside for the cap to fit. I may have to use thick wires from the cap directly spliced into the 5V wires and grounds of the ATX plug to connect the cap. Then I want to use a zip-tie to hold the cap to the wires and away from the motherboard.


Call me old school, but I go for the brute-force approach with most of my electronics, big caps, transistors and heatsinks when I want power.

 

[EWorkshop1708]

Oh, to stick with the thread on cheap parts failing..............

That's why we DIY! We can replace these with better lasting and higher spec parts!

To the thread starter, If I were you, I'd change a few of those caps, and check transistors instead of junking that supply.

 

[guitar_joe]

sure you can do the mod, it probably won't cause anything drastic to happen.

I just don't see the advantage of adding more caps to the power supply, if the circuit does the job theres no real need to improve it.

It reminds me of when people put massive caps in their audio amplifiers. sure it would probably improve test figures with continous full power sine waves but normal 'music' isn't quite like that and much smaller caps will do just fine. This is the voice of experience talking...

I started the thread and i really wanted to fix the supply however...

The parts i needed to replace were so badly burnt / decapitated i couldn't identify what types they were.
It was a piece of junk anyway

 

[megajocke]

The capacitance is usually more than enough even from the beginning. Adding much more capacitance can upset the feedback loop.

 

[guitar_joe]

i tried to tell him