Zalman ZM600-HP repair for spare PSU

[Tremmor]

Hi!
I got my second Zalman ZM600-HP PSU broken some time after warranty period. If I recall it correctly it was one morning blinking blue led and fan was turning on and off, computer didn't respond to power on/off button even for a second. I replaced it with other power supply and computer worked like it should.

Now I need a bit beefier spare power so instead of burning money for new PSU that propably works only a couple of years before giving up I decided to give it a try to fix this myself. Fuse seems to be ok, no obvious bloated or leaked caps an eye can spot, ESR-meter measured all but Teapo 420V 390uF input capacitor ok, no resistance between pins when soldered out, no esr reading either. This cap was slightly domed and it looked normal and felt normal in board. I ordered 390uF 450v Rubycon Capacitor 105'C 9216AW from Ebay to replace it. There was a bit brown color under caps negative pin in board and under one row of 3 legged mosfets or transistors (Q) that were screwed into long heatsink with one diode but they measured ok if I got it right.

Later I made a search for 3300uF 16V caps as well, and since I couldn't spot them at Badcaps or TheCapKing my spiderpigsenses started to tingle because they were available at ebay. A bit reading made me sure that I ain't getting real thing.

Would this cap work: 470uF/400V/105C? No idea about manufacturer thou, price is about same with other bigger caps in Mouser or Digikey but postage and packaging is way cheaper so I'm tempted to buy this instead of ordering cap from abroad.

What should I check while waiting replacement cap to arrive? I'm planning to load it with few old harddrives at bench for measuring voltages before connecting to system so in case of failure it doesnt kill too much hardware.

[c_hegge]

Yup. a 470uF 400V Input cap would work fine. Just test the capacitance to make sure it really is 470uF, though. If you're getting it from fleabay, it may very well not be.

[Tremmor]

Update:
Allrite, got capacitor and PSU tester I ordered some time ago.

New capacitor is Samwha and its shorter but with bigger diameter so it didn't fit without soldering additions to legs. It measured 0.1 ohm with ESR-tester. Since cap came slightly over pcb I had doubts if it will fit in casing. It did, but the question should have been "Will top fit after soldering cap?", Nope, not without placing fan ouside. It was delightful to realize that :P

After tightening screws and shakedown testing I plugged it into mains and PSU tester, no bang or smoke when switching on either which was nice.

Googled ATX psu specs and 3.3V line is giving 3.5V according to tester and dmm verified it, 12V gives 12.54 with dmm and is within specs. It seems I need to open PSU again and try to locate 3.3V line and study the matter a bit what is causing too high voltage in 3.3V line.

[Tremmor]

Update:
I've come to conclusion that 3.5V is so close specs it doesn't need remedies unless someone convinces me otherwise. Thanks C_Hegge for showing green light for cap size in first post.

http://en.wikipedia.org/wiki/ATX

[Behemot]

I have 3300uF/16 V D10 caps if you need.

As for +3,3 V, ATX specifies +-5 %, that is 3,465 V max.

[Tremmor]

Update
When I put single hard drive as load, psu tester alerted that 3.3 line raised to 3.6V, other lines didin't change. I replaced all secondary side electrolytic caps, none of them seemed to be bad thou and to do so I had to remove heatsink so I tested schottky rectifiers (figure 17 in link) as well but I couln't them bad either.

http://www.hardwaresecrets.com/artic...y-Review/402/6

Next I'm going to replace Samwha input cap with 390uF 450V Rubycon as this testek ok. My guess is that problem lies in secondary side since no other lines are affected and therefore should be easy "remove, test, replace-task", right? At least there aint hundreds of components to mess with. =)

[c_hegge]

It could be just because it doesn't have enough load on that rail. If you have a spare old PC, then try it and see what it does there.

[pdavid]

These FSP GLN, HLN, etc. platforms always give you higher than normal 3.3V if the unit is not properly loaded. A psu tester won't do much, but using a motherboard+cpu+hdd as load the voltages should be in atx spec. Still, if the 3.3V line is too high and you don't want to risk overvolting good hardware then this is what I recommend:
I've experimented with the regulation of these units, and there are plenty of options if you want to adjust the 3.3 rail. The easiest is just a minor modification.
Look for two (blue) resistors where the 3.3V sense wire is attached to the pcb. There is also an tl431 around. Just replace these two resistors with a trimmer pot of proper value and that's that. You can manipulate the regulation of this rail (to some level).

I hope that helps!

[cheapie]

Originally Posted by Tremmor

Update
When I put single hard drive as load, psu tester alerted that 3.3 line raised to 3.6V, other lines didin't change

It appears to be group regulated, so that makes sense. It needs to have a load on +3.3V for it to be in spec.

[Behemot]

Very likely it is +5V regulated with magamp'ed +3,3 V.

[pdavid]

Right you are. So the other option to modify the 3.3V output is changing the mag-amp choke. But with unknown parameters... that's a guessing game.

[Behemot]

I tried playing first with feedback, than with magamp choke once in a crappy PSU, the result was even worse than before. In the end it ceased working at all…so this is not really easy.

[kc8adu]

many fsp have an adjustment for +3.3
or just load it and see if it settles.
recap the secondary or you will be back in it soon!

[Tremmor]

Thanks a lot for suggestions, unfortunately I had minor setbacks with repair since I have more enthusiasm than skill, but live and learn =)

I set old computer with psu, it powered on for a maybe 20 secs then shut down. Then i couldn't get mobo power on with other psu's either, no fans running. Got zapped a bit when removed fan casing (psu off), might have touched heatsinks on edge with casing so that might be cap discharge.

Zalman didnt start any longer with PSU tester so i tested fuse and it wasnt broken, while doing that i noticed 1 long uncut cap leg was bent on board, grrrr. Tried to test it again but no go.

Rushed removing top case and saw spark thrown on table and switch fuse blew (at least it works!), I noticed that spark came from heatsink shorted with coil and one of the caps I replaced on secondary had paint scraped off when placed top back on. Heatsink wasnt screwed on casing and clearance to coil is minimum, so I prolly touched it causing it short with coil. Something was learnt in process...