[Coco] Re: 512k CoCo 3 with 6309 on ebay (Mike Pepe)

Robert Emery theother_bob at yahoo.com
Thu Jun 16 11:38:23 EDT 2005

> > Dave wrote:
> >> Nice machine Mike!
> >>
> >> Where did you pickup the 5V off the board for the fan and any current
> >> limitation?
> >>
> >
> > Right off the main power transistor. The power consumption is really
> > quite low, though I usually like to run 12v fans off the unregulated DC.
> > Only annoying thing about that is the busier the computer is, the more
> > that unregulated supply sags, and the fan's speed drops. I guess its
> > like an audio cpu load meter.
> Ok, so I was not hearing things :-)
> I hooked up a small 12 vdc fan also to the unregulated side of the power 
> supply to try and avoid as much as possible overloading the already taxed 
> regulated side of the CoCo 3 ps.<snip>
> Depending on what I was doing while using the CoCo the pitch noise of the 
> fan would definetively change, and I figured the pitch change was a result 
> of a speed change due to a fluctuaing unreg 12Vdc as the load from the CoCo 
> electronics shifted.
> While my current internal fan does cool off pretty well the CoCo, it is very 
> noisy and currently I am in the process of setting up a new fan in there, 

On my portable CoCo3 I hooked a 12v PIII CPU fan up to the regulated 8v power.
This dropped it from a bit noisy to a faint whisper, and it still cools quite
well. At 8v it's drawing only about 40mA, and a finger on the 8v regulator
feels barely warm.

I have a floppy drive running off the CoCo's 5v regulator, as well as a small
amp/speaker, Turbo LED circuit and an inverter chip (which lets me swap sides
of the 3.5" disk). I plan to replace the 5v reg. heat sink with a finned one,
and the fins are angled to "duct" the air towards the fan, which is already
pulling it out the top of the case.



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