very cool story, and i'ts good to know that when the fans in my
decstation(s) eventually fail, i'll know what kind of fans to look out
for. these machines are truly wonderful. :) 
happy hacking,
isildur

On Wed, 17 Mar 2004, Wai-Sun Chia wrote:

> Just wanted to share my experience with the maintenance of my DS5000/260 
> power supply...
> 
> Just acquired a DS5000/260 recently, but was hearing some high-frequency 
>     and loud tic-tic-tic.. sound coming from the fans. So I took the PSU 
> apart and junked the original fans (note to self: before junking 
> anything from a classic computer, take down the specs).
> 
> Since I have a bunch of Evercools (12V 0.14A), I spliced 3 units into 
> the PSUs and tried booting 1.6.2, it booted...yay!
> 
> A couple of seconds later I noticed the following flood of messages on 
> the console:
> 
> Power supply overheating.
> Power supply OK again.
> Power supply overheating.
> Power supply OK again.
> Power supply overheating.
> Power supply OK again.
> Power supply overheating.
> Power supply OK again.
> Power supply overheating.
> Power supply OK again.
> Power supply overheating.
> Power supply OK again.
> Power supply overheating.
> Power supply OK again.
> Power supply overheating.
> Power supply OK again.
>         :
>         :
> 
> (over the course of 2 or 3 days)
> I found out that this is coming from a bit in the IOASIC register which 
> seems to be toggling 1 and 0 at a quick rate. I figured if the PSU is 
> really overheating it'll be a steady "overheating" messages, so my case 
> seems to be a borderline case..
> 
> I felt around the PSU and noticed a patch which is warmer than the rest, 
> near the front led, so I decided to replace that fan with another from 
> my spares, a NMB 12V, 0.3A (very powerful little bugger, the only one I 
> had). After which that area was cooler than before, nevertheless, the 
> messages still showing up..
> 
> The next day, I scoured the shops nearby hoping to find another 0.3A fan 
> like the NMB, but failed. All I found was a couple of Panaflos which was 
> 0.25A, which was not that shabby I thought. What the heck, I bought 3 of 
> them.
> 
> Well, after replacing the remaining Evercools with the Panaflos, the 
> messages stopped!!
> 
> And the moral of this story is:
> When it comes to fans, size matters (CFM -wise), the DS5000 PSU's 
> thermal sensor is very sensitive as it is an IC-type and not NTCs like 
> in regular el-cheapo peecee power supplies.
> 
> OBTW, I love my PMAZC-AA (dual SCSI) controller, it's fast! :-)
> 
> 
> 
> 
> -- 
>            a8888b.
>           d888888b.
>           8P"YP"Y88       Wai-Sun "Squidster" Chia
>           8|o||o|88       Technical Consultant (RHCE)
>           8'    .88       Linux/Unix Development
>           8`._.' Y8.      Consulting & Integration
>          d/      `8b.     HP Services Malaysia
>         dP   .    Y8b.
>        d8:'  "  `::88b
>       d8"         'Y88b
>      :8P    '      :888
>       8a.   :     _a88P
>     ._/"Yaa_:   .| 88P|
>     \    YP"    `| 8P  `.
>     /     \.___.d|    .'
>     `--..__)8888P`._.'
> 
>     "Phear the Penguins!"
> 
> 
>   "I'm not out to destroy Microsoft.
>   That will just be a completely unintentional side effect."
>   - Linus Torvalds -
> 
> 					
> 					
> 					
>