12 Jun
2009
12 Jun
'09
8:46 p.m.
Eric Smith wrote:
I wrote:
Just to note, micas can suffer from metal migration as well.
I don't think ceramics are likely to have
gone bad unless
they've been subject to extreme mechanical shock.
dwight elvey wrote:
The older ceramics are notorious for going short
when used
in low current applications. As bypass caps they would self
remove the short because of the current. In low current
applications they just become vary leaky.
Having worked on pinball machines, I've replaced a lot
of these bad caps when used in the switch inputs.
I've also replaced a few when in the services on radio
equipment.
I'm told it is related to metal migration.
I stand corrected! I've never observed that problem previously, but now
I know another thing to watch out for when restoring old machines. I'll
have to mention this to the other guys on the PDP-1 team. Maybe this
might be one of the problems with the notoriously unreliable pulse
amplifier modules. On the other hand, they were notoriously unreliable
even when new.