Conference hydra::amiga_v1

Designing a circuit is no big deal (probably be fun), it's figuring
out where to place the thermistor (actually I'd prefer the average or max 
of more than one thermistor...)

john

    I assume the circuit would keep the fan at a slower speed until
    exessive heat causes the sensor to trip and run the fan at normal
    speed. placement should probably go near the center of the unit,
    or near the most important device in the card cage. If the sensors
    are small, perhaps the individual user could "stick" them in the
    important area of choice?
    
    
    My system, even with an almost filled expansion area, doesn't come
    close to getting hot because the fan is soooo strong. A certain
    rating of resistor might work well enough -- although personally
    I like the circuit idea better.
    
    
	Gonna give it a shot John?

Well, here's a quick guess. Check out:

	wjg::amiga:fan_ctrl.ps		(postscript)


No numbers, just concept.  Maybe a hardware type could tell us if it
might work...

I'm sure this has been done (correctly!) somewhere.


john (software engineer)

    
    I'm expecting to receive a blurb on a Mitsubishi thermoelectric fan
    like that used in the A3000.  I'll post specifics here if and when it
    comes (I circled one of these little reader service cards).
    
    I installed an Interfan part number mumble in my A2500 and it's nearly
    silent.  The whir of the hard drive is louder.
    
    Ed.

    
>    I installed an Interfan part number mumble in my A2500 and it's nearly
>    silent.  The whir of the hard drive is louder.
>    
>    Ed.

number mumble? Where'd ya get it?

john

    I would advise getting a quiter fan before wiring up thermosensors in
    your computer. Without constant airflow through an enclosed case, "hot
    spots" will develop around the chips. If you want to do thermocouples,
    you can't really just hang them in the air, you need to stick them onto
    actual devices. Then, to do it accurately, you need to put silicon
    grease on the thermocouple/sensor interface to allow heat transfer to
    take place. The air temp in the case will only go up a few degrees even
    if your CPU is in danger of buring out... so you really do have to put
    sensors on the devices most likely to heat up. 
    
    bob pomeroy
    refine::pomeroy
    
    

    I've seen notes on a "stealth" fan modification floating around Usenet. 
    (Of course they're not anywhere handy right now.)  The modification was
    basically to drill out the fan mounting holes slightly, insert rubber
    grommets, then reinstall the original fan.  This kept the noise and
    vibration of the fan from being coupled into the chassis.
    
    When I've come into contact with fan selections in the course of
    product design, there is a recurring theme.  Power dissipation, air
    moving capacity, noise: optimize two out of three.
    
    Wes

>   (Of course they're not anywhere handy right now.)  The modification was
>    basically to drill out the fan mounting holes slightly, insert rubber
>    grommets, then reinstall the original fan.  This kept the noise and
>    vibration of the fan from being coupled into the chassis.


I tried that. I even tried the Radio Shack fan route... No avail!

I agree, I'd much rather find an alternate solution than to mess with 
thermistors (as I noted earlier, you'ld need more than one strategically
placed to be safe)


john

    Re: .4
    
    Ed - are you happy with it? What is the part number and where did
    you get it (and how much $$$)?
    
    Keith

    
    I won't be able to tell you the part number for a week or so, since myu
    entire office is packed away into little boxes for the move to SHRIII
    and my Amiga is cabled away under my desk at home.
    
    Ed.

    I'm going to be opening my system tonight and I'd like to try placing
    a resistor on the fan to slow it down a bit. Since I'm a not hardware wiz,
    especially when it comes to placing circuits on AC lines and power
    supplies, Can anyone suggest what rating resistors (or a range)
    I should try? I assume it's a "power" type, but what wattage, etc.
    Also; I have seen two "styles" - the "tan boxy" type and the common
    "hour-glass" with color codes. Does it make a different which should
    be used?
    
    			Please excuse my ignorance, Keith

    
    Careful! Adding a load to the line can cause the Amiga to shutdown.
    I know this for a fact since I have a potentiometer in the line to the
    fan. It took a couple of bad guesses to get a value that wouldn't cause
    the Amiga to shutdown. At any rate, slowing the fan down too much WILL
    cause overheating if you have an A2620-equipped system box. Also,
    during the summer, when heavy electrical usage reduces the voltage to
    the system box, the fan can be slowed too much resulting in
    overheating.
    
    -Paul
    

> I'm going to be opening my system tonight and I'd like to try placing
> a resistor on the fan to slow it down a bit. Since I'm a not hardware wiz,

Just a suggestion.  Don't do this!!!  Especially if you have a hard drive!!!
I don't want to go into this in depth.  But if you have a hard drive and you
agravate any ripple which might be in your supply, your motor will HATE you
for the rest of its very short life!!!!!!!!!

Go the quiter fan route, even if it means waiting a few extra days/months.

Once again, DON'T load the 12V (which feeds the fan)!

Again, this is just a suggestion!

If you have a RODIME hard drive, you can kiss your motor control IC goodbye if
you ignore this suggestion!

Sorry to damper your spirits, on this, I know that 'little' noises can be really
agravating.  Still, I think that just cranking a resistor in line with the fan
is one terrible idea!

Clark Williams (TOPGUN)

	I'm also not sure how placing resistance (or even
    disconnecting the fan altogether) would cause voltage problems for
    the rest of the system (unless you were going to place it in parallel
    :-) ).
    
    Hummmmm. What then is the solution to a fan that's overly strong
    and too noisey? Has someone found a good substitute? How did the
    potentiometer work out?

	So Ed, what was that part number?  The bearings in my fan have started
to go, and it makes a racket that makes its original noise level seem quiet.
I've got to replace it, and I'd rather add a quiet fan.

Mark

    
    Ah, I knew I'd forgotten something!
    
    12 VDC brushless fan
    PN PO025-120-3B
    
    Glynn Electronics
    91 Clay St.
    Middlebore, MA 02346
    (508) 947-4262
    
    Ed

    A question for those of you that have replaced your A2000 fan.  What is
    the name of the manufacturer of the fan that you use?  The previous
    note mentioned a fan, PN  P0025-120-3b, from Glynn Electronics.  Does
    this part # correspond to the Interfan mentioned in a earlier note?
    
    mark
    

    
    Yes.
    

Does this new fan make that much difference?

john

Before leaving work today, I thought I'd fire up DECnet on my Amiga and copy
a few archives over.  When I picked up the keyboard (resting on the system
unit), I thought "this sure seems hot".  I touched the system and sure enough,
it was very hot.  Hey, wait a second - I don't hear the fan!

Normally, people complain about fan noise, but I think my DECstations 
expansion boxes are considerably louder.  Loud enough that I didn't notice
when my fan stopped working.  Maybe last week, maybe over the weekend, maybe
today.  After removing the cover, the HD case and critical components like
the 68020 were too hot to touch!  The machine appeared to be running fine!

After removing the power supply case, I discovered that the fan motor was
not the culprit.  Somehow the plastic fan piece had cracked and slid off the
motor.  All I really have to do is find a replacement.  Worst case is to
get a new fan (drilling out the rivets, argh).

Anyway, I was suprised that the machine kept working even under such bad
conditions.  A couple more hours and I probably would have had some
serious problems...  

Steve - maybe I need a thermister based cutoff circuit!

Re: .20

I hope that there is no long term damage.  As I understand it, one problem
with running a system hot is that it may shorten the lifetime of components
and cause them to fail after the heating problem is fixed.

    I replaced the fan in my A2000 with the Interfan PN P0025-120-3d.  It
    really made a big difference.  I cannot even hear the a2000 now.  The
    fan cost about $12.00 at a local electronics supply shop.  If you want
    to quiet your a2000 this does the trick.
    
    md
    

Re: .20

>>Before leaving work today, I thought I'd fire up DECnet on my Amiga and copy
>>a few archives over.  When I picked up the keyboard (resting on the system

DECnet?  async perhaps?  I'm currently putting together a uVAXII W/S to take 
home that will sit beside my 2000.  How can I get DECnet running between them?


...Ed

I have run asynch DECnet in the past, but for a long time now I've had
an ethernet board in the 2000.  There are a couple of notes that describe
the DECnet software for the Amiga - dir/title=decnet should find them all.

Steve

    Re: DECnet
    
    I've been running with ASYNC DEcnet to a local uVAX 2000 and have had
    several problems (mostly that it works for a while, then dies.
    Especially file transfer). I have never gotten a dynamic terminal
    switch to work over modem either.
    
    
    Re: Interfan
    
    Is everyone sure about that part number? I've called several places
    (including the Interfan Co.) and there is no such part, but there is a
    PN P0025-12D-3b
    
    Keith
    

    The correct part number is P0025-12D-3B this is the fan I am using.
    
    md