NCR Tower PSU again

From: Jules Richardson <>
Date: Thu Dec 2 11:53:39 2004

> >
> > Nice bodge story: I just found out why the system wasn't starting up at
> > all. It had been semi-dismantled since it had died years ago; I'd
> > reassembled it recently when trying to get it running again.
> >
> > After much wiring tracing I've just discovered although the cable
> > between the control panel and the backplane is keyed at both ends, at
> > one end the connector was on back to front. That hadn't stopped whoever
> > assembled it at the factory from hammering the keyed connector backwards
> > into its socket!
> Argh!. You want to find the idiot who built that system and connect his
> private parts to selected points on the mains side of that PSU :-)

Yahuh. I'm going to tie a label to that cable to remind me to connect it
backwards the next time the machine's in bits - grr!

> I would therefor try a respecable load on the 5V line and see what happens!

Turns out my series light bulb was screwing it up when under a slight
load (rather than free running) and causing it to stop-start, although
I'm not quite sure why. Ditching the lightbulb and replacing with a 4.7
ohm / 5W resistor sorted that out and it all sprang to life :-)

I still need a proper 10 ohm resistor to replace the one that failed (I
nuked my only spare too) - I'll scrounge on off the Colossus guys...

Looking good though :-)

cheers for all your help,

Received on Thu Dec 02 2004 - 11:53:39 GMT

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