First post, by nztdm
I have done a few re-caps before with success. I succeeded with the power brick of my Compaq SLT/286 which went up in smoke.
I just acquired a Compaq Portable 2, and would like to fix the dead power supply. I notice nothing out of the ordinary, except the 1700uF cap looks a bit dodgy. Replacing just that with a general purpose 2200uF I had lying around made no effect.
The symptom of the dead PSU is:
Turn it on and you just hear a 2Hz click sound (not a relay). Turn off and the clicks get more sparse, and turn into short buzzes, before finally trailing off into a final long squeal.
With each click, the power rails come up to almost their desired value for a short moment. Correctly, the PowerGood signal is never activated. And as expected, the 12V fan doesn't budge.
I removed all the electrolytics, and will order replacements from Digikey tomorrow. I have some in my cart. I just chose ones with the highest ripple current, 105°C, same lead spacing, and as close to the large original sizes as possible, with values within 10% of the originals.
I am no capacitor expert, I just got the impression from reading online that that's the kind of caps you want in a SMPS: ones rated for high ripple.
I did manage to find datasheets for some of the original caps, but often had trouble comparing to modern caps.
I've made this, as I couldn't find anything similar online. Hopefully helps someone out there.
Here are the caps I'll be replacing:
1) 2 x Sprague 81D: 330uF 250V
2) 3 x Nippon Chemicon RX: 470uF 25V
3) 1 x Sprague 672D: 410uF 25V
4) 1 x Sprague 678D: 5700uF 6.3V (5V output filter maybe?)
5) 1 x Sprague 672D: 1700uF 20V
I'll replace them with:
1) 2 x Vishay MAL225953331E3
2/3) 4 x United Chemicon EKZN350ELL471MJ20S (this replaces the three 470uF, and the 410uF)
4) 1 x United Chemicon EKY-160ELL562MMN3S
5) 1 x Rubycon 35ZLJ1800M12.5X35
Any experts got any advice?
Thanks! 😁
Would be nice to get this power supply going. If I fail, I'll modify an ATX power supply, as I have the pinout:
Note: all removed caps measure correct on multimeter capacitance mode. But I don't have an ESR meter at present.