Re: Question about Sun Rem SCSI card

Luke Goembel wrote:
> For instance, you show a fan installed
> under your 1.5MB memory board on
> http://www.lisa2.it/2Meg.html
> and
> http://www.lisa2.it/XLerator.html
> I have a fan installed in my Widget
> drive cage. Do you know if the Widget drive
> cage fan provides enough circulation to
> cool the 2MB memory board or would a
> second fan be required?
> ...
> All of this
> leads me to believe that it is prudent
> to have forced cooling (a fan)
> with the Lisa, contrary to what I've
> read elsewhere (E.g.; "there is no need
> for a fan to aid cooling",
> http://lisa.sunder.net/LisaProjectDocs.txt).
> Perhaps dissipative cooling was
> fine when Lisa's were brand new,
> but aged Lisa's with drying out
> thermal paste and aging electrolytic
> capacitors might have their lives
> extended with cooling.
>

That's correct, it is prudent to add cooling to a modified, or even just aging Lisa.

The text that you're referring to is this:

     >From a hardware point of view, the Lisa has a high quality     design. All the
    components that are safe for a technician as well as a user to     access and
    replace. Since the components are properly designed, there is no     need for a
    fan to aid cooling; the Lisa uses convection cooling. Every     component is
    modular in design.

To add back in the context of that into the discussion, the above text comes from the 1983 Lisa Hardware Guide, and it was probably written before the Lisa made its way to market.

Considering that the Lisa's clock lasts until 1995 before it rolls over, I highly doubt that Apple intended them to survive for 25+ years, and in this current age of planned obsolescence, I'm very happy that a lot of Lisas have survived this long. (And I haven't even mentioned how soon after the Lisa introduction they were taken off the market.) :-)

When it comes to a Lisa that has had extra devices added to it, those extra devices will certainly draw more power and generate more heat than was designed for the chimney effect in the Lisa's case to handle.

I don't know whether any thermal paste was used inside Lisas, I've not noticed any in mine - they're common inbetween CPU's and their heat sinks, but stock Lisas don't have heat sinks - I suspect the case would act as a heat sink, but there's no heat sink in the modern sense of the word, so probably there's no thermal paste either. (Perhaps the XLerator boards use them.)

Once the Lisa 2/10 was introduced, the thermal flow changed, infact, they needed new power supplies to handle the load of the widget drive... I believe they even added a fan under the Widget drive to help cool it.

One of the things James suggested to me when I replaced the capacitors in two of my dead power supplies was to add a small 12V fan inside the PS and run it at 7V (the +12V and +5V would provide 7V) - alternatively just 5V would be enough - but be careful you don't use the 5V that's used to power the COP421. The fan certainly helps the longevity of the components in the machine. Certainly using the 1.8A power supply is better for the Lisa as well since it can draw as much power as it needs.

If you don't want to modify your Lisa, you could also mount a small fan above on the vents behind the Lisa, but make sure it's a shielded fan as the RF from the fan may cause some interference with the display - a fan inside a metal wire mesh will work fine, and still allow air flow - you may have to clean the mesh of dust every once in a while.

But sure, for a brand new 1983 stock Lisa 2, with no hard drive, and no extra hardware, and no intention to have it last more than 5-10 years, and an Apple Warranty, chimney effect cooling is fine. For Lisa owners in 2008, not so much. :-)

Personally, I have two Lisa 2s, one in perfect condition, and one with a bunch of repairs I've made to it. I almost never power them on. If I can use the emulator for something, I use the emulator instead. I do occasionally power them on for an hour or so just to make sure that I know they're working, and if not so I can fix them. Running them all the time will increase the chances of component failure. This is especially true of mechanical components such as floppy and profile drives.

My suggestion is as follows - have adequate cooling for your Lisa - in my case, I keep my computers in a room with an air conditioner running at all times (even in the winter), I keep my Lisas unplugged when not in use (since the Lisa's power supply is always running when it's plugged in), and when they are in use, they're plugged into a good APC UPS.) Received on 2008-07-27 09:29:13