[time-nuts] OT- Fixing product by attaching the scope probe

David Forbes dforbes at dakotacom.net
Wed Nov 28 15:51:24 EST 2007

Chuck Harris wrote:
> Ah yes!  You gotta love it when the test instrument fixes
> the problem ;-)
> I recall hearing of a few instruments that had scope probes
> built in to fix strange parasitic problems...
> -Chuck Harris

When I designed and debugged VMEbus cards, I would joke about doing that 
sometimes when I found that the scope fixed the problem. The joke got 
more involved, however, when the board only worked properly with 100 
channels of logic analyzer probes connected. Shipping a board with that 
much stuff stuck to it might make the customer nervous. So my boss 
always made me find the source of the trouble.

We did ship some boards with rows of 150pF SMT capacitors on register 
select inputs of an IDT bit-slice ALU due to a die shrink that made the 
internal registers get corrupted with fast incoming edges. Talk about 
analog solutions to digital problems!

--David Forbes

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