ajp166 at bellatlantic.net
Sat Jul 2 15:48:18 CDT 2005
>Subject: Re: VT-131 prints?
> From: shoppa_classiccmp at trailing-edge.com (Tim Shoppa)
> Date: Sat, 02 Jul 2005 16:31:04 -0400
> To: cctech at classiccmp.org, cctalk at classiccmp.org
>> buy a bag of 100V caps
>That white-ball with wires is supposed to be a fast-recovery diode.
>It gets hot, as you can tell by the charred PC board around it. Replacing
>it with something beefier (but it has to be fast-recovery!) never
Actually it gets hot due to the cap shorting or going leaky. Then
the diode and an associated resistor start heating excessively till
the cap shorts completely or the heat causes the diode to short.
It's a single point failure that was due to a underrated part (cap).
I was with TSG (Terminal Systems Group) when they discovered they
were getting killed by field failures of 1.7 years in service
(average age) VT1xx video modules. All because someone wrote
50V not 100V for the electrolytic used.
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