Removing the A4000 power supply fan?

[mechy]

Hi,
 
Just a thought. I like silent computing and my Amiga 4000 has a power supply fan blowing air the wrong way. It's a known problem that quite a few A4000s are constructed this way, the fan is blowing hot air into the power supply and not out of the chassis.
 
Now, my questione is this: is it a very bad idea to just remove the fan completly? This A4000 is quite cold, the CPU is a 68060 (CyberStorm MK2) clocked at 50 Mhz. What risk would I be running? I guess the 68060 wouldn't overheat, but what about the power supply?

As others have said, the fan cools the entire machine, accelerator and zorro cards. do not remove it or everything will overheat-The psu may die first.. I have been using Noctua NF-R8 fluid bearing fans in them and find they give a cfm increase as well as being much quieter than the original. Its also not a good idea to slow the fan with resistors,as cfm decreases exponentially with speed i believe.

[mechy]

Back when they came out, that was a big problem for people in some regions. I remember usenet posts from people in Australia that could not use their new A4000D's in the summer! If you are in Norway, could be a different situation. I know Sweden had to retrofit the coastal patrol submarines they exported to middle eastern countries to add air conditioning - they had never even thought about AC when using them off Sweden, they needed heating.

The stock A4000D ps CBM bought is junk, although many are still running. LoadWB is right - the only limitation is form factor, there is only so much room inside the case. I mounted my replacement -behind- the case, behind where the ps normally goes, and used a cantilever system to support it. This consists of, on top, two steel bolts with curved hooks on one end to catch the back of the ps, and the threads and nuts on the other tensioning (is that a word?) it unto the case. The ps fan still draws air through the case, and now I can use just about any supply I can find. I should post a picture.

Years ago, when I had too much time on my hands, I made my A4000D totally silent. I got a bunch of surplus Linear DC power supplies, one for each needed voltage, probably from old minicomputers. Each one was half as big as my A4000D, and twice (or more) as heavy, and I needed three (+5V, +12V, -12V). Put them on a shelf below and used automotive starter cable (big as your finger or thumb) to get the power to the motherboard. These supplies had big fins for passive cooling , no moving parts! Left the case off the Amy Was wonderful, but when time came to move, I could not take the beast of a setup  Went back to ATX setup described above.

The stock 4k psu's are not junk, as a matter of fact they have the exact same switching topology as modern psu's and of AT ones of the day. I do prefer the skynets to the liteon versions(easier to recap at least) however, both work exactly the same way as any switching psu.The fast that most of these psu's made it 15-20 years is pretty amazing.  If you want to see junk go thru most of todays atx,itx etc. very poor caps, little to no filtering,high ripple and poor +5 regulation. this is so common now its not funny, even some of the so called name brand 80+ certified atx psu's bomb. put a high quality fan with more cfm than the stock one and most all problems go away.

[mechy]

Just a quick note.. Get a quiet fan and have it point out of the chassis! The fan should not blow it's hot air on the cards or anything else.

The fan should draw thru the front and distribute around the cards cooling them and add the PS heat before exit...

If you look at the 4000 case design, it does not pull any air through the front,it can't because for the most part the front bezel seals it all off(well not perfectly,but pretty well)..
 Air enters the back of the case through the holes near the slot brackets,moves over the cards towards the front, goes around the zorro slot board at the front, and over the accelerator and into the psu and out the back of it. A little if pulled over the HD's but its almost a dead spot for air where the HD's are.

Some people add slot fans between zorro boards but it can actually fight the psu fan and make cooling worse.

One way to improve cooling is use the slot covers that are perforated with holes.It gives more area for air to come in. This works if your slots are not all full of cards.

The Noctua nf-r8 fluid bearing fan i mentioned earlier gains 5 more cfm than the stock amiga fan and is very quiet. They seem to last forever when kept clean.

[mechy]

Thanks for the great explanation.

I never put time into my 4000d really and that info helped.  I need to find a smaller cd rom cause I really don't know how any air gets moved in the system.

I assume that fan you recommended works in a 3000d power supply also?

 I think the 3000 uses the same one as the 4000 but be sure to measure it, I dont have a 3000 psu in handy to check.

As for cdroms that are short, the SONY drives like crx320E(dvdrom+cdrw) ,crx230 series(cdrw),and crx230A work well..
ebay example:  http://www.ebay.com/itm/Sony-CRX230A-CDRW-Internal-IDE-Drive-TESTED-/262365859076?hash=item3d16394d04:g:pasAAOSwJb9WrmPq

or black drives if the color makes no difference: http://www.ebay.com/itm/DELL-NP873-IDE-48X-CDROM-GENUINE-PRECISION-WS690-OPTIPLEX-320-PHILIPS-DH-48N1P-/251188734686?hash=item3a7c03eade:m:mXuv-PpS_8lsr-ThfvrggUA

longer drives also work but a right angle power plug will make life easier. i have found these long drives really dont hinder cooling too much in basic systems with a few cards.. obviously if its a toaster system with hot drives its not ideal.

Beware not all DVD/CDRW combo drives seem to work on amiga, but the sony's listed above worked for me.
This cable might give you perfect clearance on the long drive and keep the power connector from hitting the psu. I have used these alot when only long cdroms were available.
http://cdn.opentip.com/Electronics/Monoprice-Molex-Molex-p-1515249.html?gclid=CMjcrKzA8csCFQoNaQodHUQHqw

[mechy]

@Mechy

Thanks for the suggestions.

I'm using a SCSI  cdrom off the warp engine, never been a fan of ide.  Any suggestions for a SCSI model?

This box has a warp engine 040@40MHz, a cv64/3d, ariandne nic, and melody z2. It uses one of those scsi2sd cards for the hd.  Would you even bother with the smaller cd?

Scsi on the accelerator is always the best way. Unfortunately i cant recall any really short scsi optical drives. i have used pioneer dr-966's alot and they work well but are long. Some nec's and sonys also,but they are all pretty much full length. Some plextors are crazy long. The old apple optical drives work well also.
from memory some toshibas had problems ripping music right but thats prob. not a issue these days.

[mechy]

I checked the Noctua R8/A8 specs, their airflow at max RPM is a ~50 m3/h.
According to data I have, the stock A4000 PSU airflow is ~70 m3/h.

Can anyone please verify ?

the information i find for the original 4k psu fan is as follows:
Matsu%&$#?@!%&$#?@!%&$#?@!%&$#?@!a Panaflo FBM-08A12M, 80cm x 80cm x 25 mm, 12 Vdc (brushless), 23 CFM

the Noctua at 50 m3/h = 29.428889 CFM

so the Noctua is roughly 5-6 cfm better.

Not sure who is right here, but i can tell you from experience in the many 4000's i own with many cards,the noctua fans make a difference and the case stays cooler.