Re: IIgs locking up after 15-20mins, TWGS likely overheating.

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

On 8/30/2010 11:21 AM, ict@ccess wrote:
> Michael J. Mahon wrote:
> > On 8/29/2010 4:50 AM, wyeo wrote:
> > > Too much draw from the power supply, if you have an original power
> > > supply, it is insufficient and the PS overheats and heats up the rest
> > > of the system.
> > >
> > > I had the same issue when I have just TWGS, RF SCSI and a sound card,
> > > it will start locking up.
> > >
> > > Either you get a heavy duty power supply (likes of Pegasus,
> > > InnerDrive, Vulcan), or the Buggie Power for a replacement.
> > >
> > > But recently, I came across an article on changing the size of the
> > > cable inside the original power supply, to push out more juice ... and
> > > jumping the power cables directly to the slots (for the serious
> > > hardware hacker).
> >
> > That's just voodoo.  You need a power supply with a bigger
> > capacity, and increasing the size of the wires won't do it.
> > (It also makes your system look like Frankenstein.  ;-)
> >
> > I suspect this superstition got started because a few folks with
> > just marginal power problems tried it and it gave them an additional
> > few millivolts, making their systems slightly less marginal.  ;-)
> >
> > Don't bother.  Get a supply with more capacity--specifically, more
> > +5v capacity.
> >
> > -michael
> >
> > NadaNet 3.1 for Apple II parallel computing!
> > Home page:  http://home.comcast.net/~mjmahon/
> >
> > "The wastebasket is our most important design
> > tool--and it's seriously underused."
>
>
> Sorry Michael!  I am jinxing your voodoo and raising you a fact.

There's always some fact that causes people to believe in voodoo.  ;-)

In this case, the "voodoo" is the notion that the bigger wires will
increase the voltage or current delivered to the main board to a
significant degree--and that isn't so.  There are other effects,
though, as noted below...

> I, myself, have replaced one of the ground wires and the +5 V wires
> with #12 gage wires inside the power supply.  Since I have done that,
> my IIGS is much more stable with a 12 Mhz Zip GS in slot 3 and a 8 MB
> serius RAM card.  I usually crashed 10-12 times a day.  Most of the
> crashes were isolated to the serius RAM card.  Since the upgrade, I
> barely even crash once per day.  I believe I can alleviate that one
> crash as well by soldering a ground wire from the ground pin to a slot
> 5 ground.  I have a CFFA card in slot 5 and a PC transporter in slot
> 7, so slot 5, 6 and 7 cards would benefit from that extra grounding as
> well as auxiliary RAM.

I'd be willing to bet that your crashes would also stop if you
connected a high-value capacitor between +5v and ground in the
vicinity of slot 7.

Big wire doesn't do a lot to increase DC voltage, but it does
decrease the resistance and inductance between the main board and
the big electrolytics in the power supply.  As a result, it is
causing the high-frequency noise to be attenuated at the bus,
improving noise margins.

A better way to bypass the main board is to put capacitors right
on the main board, as near as possible to where rapidly changing
loads occur--the Zip GS and RAM card are good candidates.  (This
is why well-designed cards have sufficient bypassing on the card.)

It sounds like your system is running on the "ragged edge" of
reliability, since a solid system shouldn't crash in weeks!  This
makes it very sensitive to very minor changes in the noise, voltage,
and temperature environment.  This is exactly the environment in
which changing almost anything can make a difference.

But a digital computer is designed so that you can change all sorts
of things by +/-10% and *nothing changes* in the functioning of the
machine.  That's the whole point of a digital machine--that small
"analog" perturbations are irrelevant to its operation, since it
has sufficient timing and noise margins to not respond to them.

Life is much better when you "back it off a little" and improve system
reliability by a huge factor.

> I haven't soldered a wire to slot 5 ground yet though because, just
> call me plain lazy, but one crash a day is acceptable to me.  :)

Wow.  To me, that's like saying my tires are fine because I only have
one blowout a day.  ;-)  You shouldn't have *any* crashes, except
possibly those due to software bugs.

> Even 1 mVolt goes a long way to make the IIGS more stable and the
> power supply strong enough for most purposes.  I have even installed a
> Version 01 motherboard into a PC tower and adapted a 200 watt power
> supply to work with the IIGS motherboard with no better results.  I
> still crash about once per day.
>
> my 2 cents worth (solder and #12 gage wire extra)

Millivolt variations in supply voltage are completely irrelevant to
a stable system.  You have at least one serious hardware instability
in yours, and I'd bet that its the ZipGS.

Many overclockers just keep increasing the frequency until it crashes,
then back off one notch.  A year later, margins have decreased to the
point where it is now crashing at the lower frequency.  Degrading
capacitors and power supplies, or increased loads (more cards) are
the usual mechanism for decreasing margins.  Better to fix them than
to "learn to live with them."

If you look inside most power supplies, there's an adjustment for the
+5v level.  Measure the +5v at the main board and adjust the pot for
5v (or even 5.1v).

-michael

NadaNet 3.1 for Apple II parallel computing!
Home page:  http://home.comcast.net/~mjmahon/

"The wastebasket is our most important design
tool--and it's seriously underused."