Dodgy IBM PC Convertible power supply

[Vintage Computer Festival]

On Wed, 15 Jun 2005, Tony Duell wrote:

> > Yes, I did this.  I can short the two leads of the switch but I get the
> > same symptoms.  There's something wrong with the electronics.
>
> When you say the 'same symptoms', what do you have to press/hold just
> right for it to work?

Good question.  Upon pondering this, I can only conclude that holding the
switch in any particular position is not really what's making it work.

I'm left with the conclusion that I am either affecting something else
mechanically (such as the contact the power connector makes with the power
socket) or there is a marginal component or circuit that works sometimes
if the right conditions exist.

The power connector (barrel type) had a bit of oxidation on the contacts
which I tried to clean and scrape away.  I got a fair amount off of it.  I
never thought to check the voltage coming out on the other end of
connector, but I'll do that tonight.

> Assuming this is an electronic problem, I would first test all the
> electrolytics on an ESR meter. High-ESR capacitors cause the most odd
> faults on SMPUSs...

I'll need to find one...

-- 

Sellam Ismail                                        Vintage Computer Festival
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International Man of Intrigue and Danger                http://www.vintage.org

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