Jerry Koniecki wrote:

Frank Miles wrote:

Tektronix was, during that time, strongly discouraging all new designs from
using tantalums. IIRC they had been taken to court over a case in which
a 465 'scope (the original, not the plastic follow-ons) had spontaneously
ignited and had resulted in an expensive fire. Forensics revealed that
a tantalum power-supply bypass cap had started the conflagration. The
drive to reduce tantalum usage was driven primarily by this liability issue,
more than component cost. If you wanted to use a tantalum, you had to
justify its usage to the component/design review committees -- which wasn't
difficult if you had good reasons and your design was solid.

Ah ha! I have a 465 (w/DM44) that I purchased in 1978 for personal use
(no commercial abuse). Shortly after the warranty expired, it would not
power up.
I traced the problem to a shorted tantalum filter cap on the +15 volt
line.
But of course, it wasn't in the power supply, but rather on one of the
boards.
Pain to get to, IIRC.

I can imagine. Tantalum caps are a real pain in the ass. If you
reverse the polarity, they burn right through the PCB after a few
months! We got a board in for repair last week with that problem.
Luckily, everything on the board (yes, even the stickers with the
serial numbers) is self extinguising.

--
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