Re: 7854 fixed, now for some newb questions


Craig Sawyers <c.sawyers@...>
 

Well done!

A few days ago I've become a proud owner of a mint condition 7854 with the calculator keyboard
(still
in its original plastic wrap). What was wrong with it - exploded capacitor in the integral EMI
filter of the
power connector. It splattered a load of brown goo on the outside, the filter itself bulged so
hard that
I couldn't pull it out at first. I was already thinking about a conspiracy of fancy US gear
against European
line voltage, but then noticed that the filter itself is "Made in Switzerland", splendid.
That is alas well known - Schaffner, the filter maker, used epoxy-potted RIFA paper filter
capacitors. After a decade or three they basically explode
https://www.vintage-radio.net/forum/showthread.php?t=88137 . They were used in vast quantities; it
they are soldered to a circuit board they just generate a lot of white smoke and a smell of hot
epoxy from the burst case. If they are a filter, all that energy has nowhere to go, with the effect
that you saw.

Chapter and verse here http://www.vintage-radio.net/forum/showthread.php?t=69128&highlight=rifa

Craig

Join TekScopes@groups.io to automatically receive all group messages.