RE: C900 and ATX Power Supplies...

From: Bo Zimmerman (
Date: 2005-08-03 19:09:06

Heh, yes, it was strange that there were no ill effects from tying the
power-on to the wrong line.  It was even stranger that, other than that
weird floating voltage, the power supply turned on and worked just fine that

Obviously, I did find the correct setting (ground instead of +5) to turn the
power supply on and keep the voltage steady.

However, it was to no avail.  I got no video signal from the computer.  I
had it hooked up to a 1084 (in rgbi mode of course).  

I'm at a loss as to where to go next.  The only doubt I have in my mind
about the new power arrangement is whether I properly measured that odd
+2.5V line.  Could someone with a C900 find out what the correct voltage on
the "brown" line is?  Or, failing that, what the correct voltage on the
"brown" line of a CBM-II machine is (610, b128, etc)?  Perhaps I measured

- Bo

> -----Original Message-----
> From: 
> [] On Behalf Of Marko Mäkelä
> Sent: Wednesday, August 03, 2005 3:39 AM
> To:
> Subject: Re: C900 and ATX Power Supplies...
> On Wed, Aug 03, 2005 at 03:01:59AM -0500, Bo Zimmerman wrote:
> > The only thing I'm doing strangely when the ps is not under load is 
> > that I cross the always-on 5V line on the ATX with the 
> Power-On line 
> > on the ATX to force the power supply to come on.  I 
> suspect, perhaps, 
> > that this might have been the wrong thing to do.
> I think it is unlikely to cause any permanent damage, unless 
> your power supply is a very cheap one made by some no-name 
> manufacturer.
> I accidentally shorted the +5V supply of my DVB-T recorder box
> ( to ground when developing a 
> power-on-by-remote circuit 
> (  The 
> power supply shut itself down and refused to start within a 
> few seconds.  The next day, I opened the power supply, and 
> the internal 10-amp fuse on the mains side was not blown.  I 
> soldered the fuse back in place, and the computer worked just 
> fine with this power supply.  It must have been some 
> overheating protection.
> Have you tried adding a hard disk as an extra load to the 
> power supply?
> 	Marko
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