Re: IIe power supply voltages

["Greg Andrzejewski" <pressyourluck85@yahoo.com>]

"Michael Black" <et472@FreeNet.Carleton.CA> wrote in message 
news:dj33lg$7v0$1@theodyn.ncf.ca...
>
> "Greg Andrzejewski" (pressyourluck85@yahoo.com) writes:
>> Hi,
>> I've been having stability problems with my IIe and suspected my "twist &
>> tape" power supply mod. This led me to wonder exactly to what degree do
>> voltages have to vary before you start seeing problems? Anyway here's 
>> what I
>> measured with my multimeter using a HD for load.
>>
>> 5v line = 5.27 V
>> -5v line = -5.00 V (dead on)
>> -12v line = -9.74 V (uh-oh)
>> +12v line = 11.23 V
>>
> Perhaps a better way to look at it is what are these powering?
>
> The key voltages are the +5V and the +12V.  The former is used by
> the motherboard and the expansion cards, obviously, and both for the
> floppy drives.
>
> The other two voltages declined in importance.  At one point in time,
> and maybe not even by the time the Apple II came along, you'd need the
> -5V to power semiconductors, like early dynamic ram.  I honestly can't
> think of much that would use it in the time of the Apple IIE.
>
> The immediate thing that comes to mind for the -12V line is for
> the RS-232 interface, which needs something like that voltage because
> RS-232 switches between a negative voltage to a positive voltage.  I think
> -9V sould still be fine, though one wonders if there is a problem with
> the power supply, or simply nobody worried about it.  After all, they
> do know what it's likely needed for, RS-232, and no that a precise
> voltage is not important.
>
> You can basically see the general useage of the various voltages in
> the specs for the current.  The +5V will likely have the highest current
> capacity, with the +12V second.  The other two will be way down in
> how much current they are expected to supply.
>
>   Michael
>
>> I double checked the +5 and +12 lines with points on the still-connected 
>> PC
>> molex connectors and they were identical to those measured through the 
>> IIe
>> connector. So I hopefully can rule out any loss where I twisted and taped
>> the IIe connector onto wires from the power supply.
>>
>> Thoughts?
>>
>> -Greg

I'll try switching the power supply to see if things improve. Another factor 
might be that they way I had the power supply installed. I hacked together 
an AT power supply for the IIe and the cable the runs to the power button 
ended up pressing rightward on my ramworks iii card. I thought if I didn't 
move the system around much it'd be okay, but maybe the card isn't making 
good contact in the AUX slot.

-Greg