Zalman ZM600-HP crackling noise

[DJduck]

Hello!

Been a while since I've posted on this forum.
I bought a dead Zalman ZM600-HP for 5€, hoping to fix it for my new-to-me AMD FX build. Powering it on at first it showed no signs of life. Opened it up and found the fuse was blown. Going down along the circuit revealed three shorted MOSFETs on the PFC heatsink and the two primary switching MOSFETs were giving funny readings as well. Replaced all five and tested everything else, everything seemed to be reading OK. Replaced the fuse and assembled the unit. +5VSB read good. Powered it on, fan comes on, lights come on, voltages are okay, everything seems good BUT there is this weird crackling noise coming from the PSU. It's not very loud, it starts out more frequent and becomes less frequent as the supply runs for a bit but does not go away entirely. I have not hooked up a load to it but letting it idle there is no weird smells and nothing seems to be getting hot or anything, runs just fine but makes this noise. I've stopped the fan to make sure it's not the fan and it's not.

Kind of like this video I found:
https://www.youtube.com/watch?v=Kf-ZXDNejlI
But not continuously and not as loud.

Any ideas what this might be? Would you trust a supply like this?

[stj]

Re: Zalman ZM600-HP crackling noise

run it in the dark and look for arcing.

[DJduck]

Re: Zalman ZM600-HP crackling noise

That is actually a really good idea.
But unfortunately (or maybe fortunately?) there is no visible arcing on neither side of the board. The noise seems to be coming from the transformer or primary side.

[momaka]

Re: Zalman ZM600-HP crackling noise

Do you have an ESR + capacitor meter? If yes, pull the primary cap and check it. High chance it's gone bad or going high ESR, especially if it's only rated for 400V. The fact that the PSU does it less when warm further suggests the problem may be cap related. Some APFC PSUs seem to kill their primary caps over time - even the Japanese brands.

I just recapped an Antec Earthwatts EA-500, and while at it, I also pulled the primary cap (400V, 390 uF IIRC). It read a bit high on ESR so I replaced it. Before doing this, the PSU was making a strange buzzing noise - even with the new secondary-side caps. After replacing the primary cap with a big Nichicon 450V, 500 uF cap, buzzing noise is gone.

That said, also check all solder joints in your PSU. Possible that a bad joint on the primary is causing arcing. And last but not least, check for tan/brown glue - the one that often goes conductive over time.

[DJduck]

Re: Zalman ZM600-HP crackling noise

Do you have an ESR + capacitor meter? If yes, pull the primary cap and check it. High chance it's gone bad or going high ESR, especially if it's only rated for 400V. The fact that the PSU does it less when warm further suggests the problem may be cap related. Some APFC PSUs seem to kill their primary caps over time - even the Japanese brands.

I just recapped an Antec Earthwatts EA-500, and while at it, I also pulled the primary cap (400V, 390 uF IIRC). It read a bit high on ESR so I replaced it. Before doing this, the PSU was making a strange buzzing noise - even with the new secondary-side caps. After replacing the primary cap with a big Nichicon 450V, 500 uF cap, buzzing noise is gone.

That said, also check all solder joints in your PSU. Possible that a bad joint on the primary is causing arcing. And last but not least, check for tan/brown glue - the one that often goes conductive over time.

Yes! Heureka!
It was the primary cap. A 420V 390uF CapXon 85C rated turd. Put in a 220uf 450v Nichicon temporarily to test it and it runs nice and quiet now. Should I go for a 450V replacement? 450v 390uf. Or should I go for a higher capacity as well? The unit is rated 600W 80+. I don't know about Zalman PSUs, been away from computers for a few years but this one looks well made, made by FSP, IIRC they were decent, no? It's got a cool heatpipe cooler
Probably wouldn't hurt to pull the rest of the CapXon and Teapo caps and put in some nice ones.

[momaka]

Re: Zalman ZM600-HP crackling noise

Yes! Heureka!
It was the primary cap. A 420V 390uF CapXon 85C rated turd. Put in a 220uf 450v Nichicon temporarily to test it and it runs nice and quiet now.

Yup, that's CapXon caps for ya! Just pulled one out of an LCD monitor last week (400V, 100 uF), because it was leaking from the negative lead. Capacitance read in spec, but ESR was going high. Wasn't even sitting behind an APFC circuit - just failed because it's CapXon bad.

Lucky I caught it in time. Primary cap failure typically leads to failure of primary switching components, as you already saw.

Should I go for a 450V replacement? 450v 390uf. Or should I go for a higher capacity as well? The unit is rated 600W 80+.

Yes, use a 450V replacement, especially if the PWM+APFC chip is a CM6800 (they have somewhat lousy APFC voltage regulation and can overshoot a decent amount - which IMO is what often leads to even Japanese caps failing in some APFC circuits.)

As for the capacity - go as high as space allows you in the PSU.
For a 600W PSU, honestly I think 470 uF or higher would be more appropriate. Except for the very top-of-the-line PSUs (even from reputable brands), most manufacturers save on production costs by using smaller primary caps.

Oh, and I suggest using only a Japanese cap as the replacement.

Probably wouldn't hurt to pull the rest of the CapXon and Teapo caps and put in some nice ones.

Yes!
After all, replacing the big primary cap would probably be the most expensive part you need to get for this PSU (probably $4-7, depending on where you get it from.) So throwing in a few more $$ for replacement of the secondary caps makes sense, IMO.

I don't know about Zalman PSUs, been away from computers for a few years but this one looks well made, made by FSP, IIRC they were decent, no? It's got a cool heatpipe cooler

I just looked up the HardwareSecrets review, and it seems like a middle-of-the-road unit: not cheap but not that special either. The only redeeming quality it has is that the review mentions it always stays quiet, even when it was overloaded to 700W DC power. That and the heatpipe cooler make it a bit more unique, so it's still worth saving, IMO. Efficiency isn't the best, but it's not bad either... and besides who cares that much for a few %. It's above 80%, so that's good enough.