More parts I need to replace on the VT100

Tony Duell ard at
Fri Dec 2 17:14:44 CST 2005

>  After some time of carefully showing the system test
> fellow a number of scope signals and carefully explaining
> the reasons I was looking at particular locations,
> I happened to glance at his notes. It went something
> like this:
> D3, D5, D8, D20, D21
>  There were no symptoms and nothing of what I showed him
> about scope information. I soon realized that he was


There is a saying in England 'Measure twuice and cut once', menaing it's 
better to re-check a measurement than ruin some metal/wood/whatever by 
cutting it too short. I would like to propse a new version

'Measure twice and solder once'

meaning you should make measurements, think about them, and _only then_ 
start changing compoennts.

> just interested in a list of parts that I indicated as
> causing problems and wasn't even paying attention to
> anything else I was doing.
>  The worst part was that since this was a one time
> parts mix up, it probably would never happen again
> so that his list was virtually worthless. I told

This is actually another problem with those lists of stock faults. If a 
fault is caused by an under-rated componet, it's likely that, after a 
couple of years, all have failed and been replaced (hopefully with a 
better-rated version). And therefore if the same symptoms occur in the 
future, the cause could well be soemthing totally different.


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