SGI Octane 747W Cherokee PSU noise

[halfloaf]

Hi,

I recently acquired a second hand SGI Octane Cherokee PSU, and while it does power on and 'work' in the workstation, it makes a rather disturbing noise. I wouldn't call it coil whine, it's more like a warbling electrical noise. The noise is from a specific area on the PSU but before I open the PSU and void the sellers warranty, I thought I'd put up a post to see if anybody has come across this before or has any ideas?

I'm quite happy to replace bad caps etc but if it's something that is likely to cost more than say £25 then I might as well return the unit for a refund. My only issue is these are becoming quite rare and hence resellers sell them for £££ hence the desire to troubleshoot and fix. (I also don't like filling rubbish dumps with electrical waste!)

The PSU has an SGI part number of 060-0035-001.

I've tried to record the sound in the link below. What you'll here firstly is the socket switch being flipped, then the relay kicking in then the warbling sound. I've tried different power cords and also wall outlets, no change.

The sound is audible from about 3m (9ft) from the PSU.

https://youtu.be/lPwTEdxI9mk

Any advice gratefully received.

Jacques

[stj]

Re: SGI Octane 747W Cherokee PSU noise

go ask on Nekochan forums.
http://forums.nekochan.net/

[halfloaf]

Re: SGI Octane 747W Cherokee PSU noise

go ask on Nekochan forums.
http://forums.nekochan.net/

I'm aware of the Nekochan forum and am a member there. While 99.5% of them can tell how to NUMA link two servers together or compile some obscure piece of code, they are a bit thin on the ground when it comes to electronic matters. Tracing 3.3v lines, yes. Diagnosing a sick sounding psu, very very unlikely.

[stj]

Re: SGI Octane 747W Cherokee PSU noise

well they would know if the sound is "normal"

[halfloaf]

Re: SGI Octane 747W Cherokee PSU noise

Hi, the PSU should be dead quiet apart from the internal fan. The fan noise is separate to this other noise.

I had one of these 8 years ago and this is by no means normal.

[stj]

Re: SGI Octane 747W Cherokee PSU noise

i had 2, but not with that psu - mine had the inferior ones.
maybe you have a coil loose.

[halfloaf]

Re: SGI Octane 747W Cherokee PSU noise

I also have an old Lucent psu, it's dead quiet apart from sounding like a jet engine (fan). It is whisper quiet in all other respects though. Cannot use the Lucent one as it does not work with VPro graphics boards unfortunately.

[PeteS in CA]

Re: SGI Octane 747W Cherokee PSU noise

Cherokee Int'l seems to be quite defunct, having been acquired by another company in 2008, which has since been acquired by some division of GE that doesn't seem to be into computer PSUs. Anyway, since your PSU is probably 10 to 20 years old, probably some output capacitors have gone high ESR, high enough to cause audible oscillation. What complicates matters, if that is the case, is that modern low impedance capacitors may be too low impedance, causing stability or oscillation problems.

IF you decide to try replacing output capacitors, use older series like Nichicon PS, PM, or PJ series. These are likely to be contemporaries or near in design age to those you would replace.

Pictures and information about the output capacitors on the PSU (values, vendors, series) would probably be helpful.

[stj]

Re: SGI Octane 747W Cherokee PSU noise

most sgi psu's are loaded with pana FC's and similar grade from nichicon.
probably part of the design spec from sgi to the OEM's

[halfloaf]

Re: SGI Octane 747W Cherokee PSU noise

I took a chance last night and plugged it in to the Octane. The warbling sound dissipates when you power on the workstation. When powering it down, the loud noise resumes. The PSU is a bit like modern ones, it never fully powers down and enters a 'power save' mode that draws about 0.2A while plugged in to the wall but turned off at the workstation side. This is sort of confirmed as the psu remains warm in one spot after about three hours of no workstation activity.

I've decided to keep the unit so will open it today, take some pictures and plug it into a wall socket to establush which component(s) / area makes the sound.

Pics to follow.

[halfloaf]

Re: SGI Octane 747W Cherokee PSU noise

Some photos. This is one of the boards in the PSU. I plugged the PSU into the wall socket and listened for the noise. The noise seems to emanate from the black Potter and Brumfield relay, or immediate surrounding components....as in very immediate. Could the yellow PTG MPX GPF capacitor (??) also make a noise?

Anyhow, here are some photos, excuse the flash, it's late...

[kc8adu]

Re: SGI Octane 747W Cherokee PSU noise

start with all the sm lytics on the small board.
hell all the lytics could be done at this age.

[halfloaf]

Re: SGI Octane 747W Cherokee PSU noise

start with all the sm lytics on the small board.
hell all the lytics could be done at this age.

"sm lytics" = surface mount electrolytic ?

Sorry not familiar with most electrical abbreviations.