powering up older machines - is it safe?

[dwight elvey]

> To: cctalk at classiccmp.org
> From: legalize at xmission.com
> Date: Tue, 3 Jun 2008 14:42:05 -0600
> Subject: Re: powering up older machines - is it safe?
>
>
> In article ,
> ard at p850ug1.demon.co.uk (Tony Duell) writes:
>
>> The main worry is not a capacitor Failing. The main worry IMHO is that if
>> there's a fault in the power supply regulation circuitry then that could
>> make the +5V line jump to a high enough voltage to wipe out just about
>> every chip in the machine. Expansive and difficult to put right.
>
> I don't disagree with the concern, but I'd be interested in hearing
> estimates on the probability of this taking place. Has anyone had it
> happen to them?

Hi
 I'd admit it is rare but it does happen. The only case I've seen
was on a pin ball machine. The way the case of the 5V regulator
had a bad connection through the mounting. This caused the output
voltage to go to the full 12V of the input. It wiped out a rare sound
chip and a couple TTLs. Not a good thing.
 This can surely happen to most any regulation circuit. Some shorts
and some opens can cause the regulation feedback path to go open.
Dwight

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