Re: TransWarp GS repair questions

[Michael J. Mahon <mjmahon@aol.com>]

Conrad <conrad.russo@gmail.com> wrote:
> Hi Michael,
> 
> Its funny that you would say that because in all my tinkering I have
> accidentally shorted the supply lines to ground on several ATX supplies
> in the past and it just caused an internal breaker to go every time. The
> supply shut off and would not restart until unplugged and plugged back in
> but once I did that everything was fine. In my most recent experience
> when I was building the -12 to -5 circuit the heatsink accidentally came
> in contact with the body of the supply with exactly that result. I guess
> I've just been very lucky! Why did you mention this though? Is there some
> circuit in the GS that achieves some result by momentarily shorting a
> supply line to ground or are you just cautioning me against carelessness
> when setting up the new supply? Either way, thanks very much!

Mostly just a general caution regarding power supplies capable of high
current output. Most traces on an Apple II (or other!) board can't handle
30A. ;-). You're fortunate that your supply shut down quickly enough--you
must have had "good" shorts to ground. A less perfect short could result in
a sustained high current. 

Although there are no intentional shorts caused by Apple II computers,
there is one unintentional situation that should be remembered. If a
joystick with pushbuttons is installed, pressing a button at the same time
as the corresponding "Apple" key shorts the +5v to ground. I haven't
checked whether a current-limiting resistor was added after the //e. 

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon