Re: AE Internal heavy duty power supplies: Questions

[rubywand@aol.com (RUBYWAND)]

In article <4p99ob$5de@disunms.epfl.ch>, dinarich@di.epfl.ch (Mirko
Dinarich) writes:

>I agree, but with a stock IIgs PS I need 2 fan in order to pull out all
>the heat generated by the computer. (well I have all slot occuped + 6
disk
>drives :-)

     If you are running any fans on the internal GS +12 fan terminal, this
could notably increase current drain. The best way to cool the GS is via a
System Saver IIgs.


>
>My problem is that when I use a disk drive the video ouput get noisy, I
have
>buy also the Heavy Duty PS but the problem remain. I've checked the data
of
>the 2 PS (the original and the HD) and the only big difference is +5 volt
>(6 Amps vs 4 Amps). I suspect that my problem is coming from the 12 Volt
>line. Somebody can confirm? 
>

     A diskette drive could be pulling enough current on the +12V line to
produce a noticeable noise voltage on this line, especially if the +12V
line is already less than 12V at the motherboard.

     A good fix try is to replace the +5, +12, and GND power supply leads
with #14-#12 gauge wire. This will significantly reduce voltage losses
between the PS and motherboard and also reduce line noise.

     On a ROM-01 machine with lots of cards, it is not unusual to discover
notable voltage drops on the Slot power lines. This is because the circuit
traces are too narrow. It may be necessary to remove the motherboard and
run +5, +12, and GND leads (approx. #16 gauge wire)  on the bottom side
from the PS plug contacts to Slots 3 and 7.


     So, there are two places where
pulling a heavy current can cause problems:

(1) skimpy PS leads result in noise and lowered
     voltages at the motherboard PS plug;

(2) narrow circuit traces result in noise and
     lowered voltages on Slot power lines.


     Some GS ROM-03 and IIe users experience similar problems with noise
and below spec votages at the motherboard. Most likely, the resulting line
glitches account for many reports of mysterious system crashes.


Rubywand