19 Jun
2013
19 Jun
'13
7:37 a.m.
Josh Dersch wrote:
I'm working through repairing a Tektronix 31
calculator for my dad
(late
father's day gift...). It seems to mostly be
working now but all of
the display
panels except for two are dead (as I understand is
pretty typical).
The display
consists of two SP-333s and four SP-332s. I've
found a source for the
SP-332s
(2digit 7-segment displays) but can't find much
for the SP-333s
(3digit 7-
segment display).
This is extremely typical of these devices. They tend to outgas over
time, and when the concentration of gas goes below a certain level, the
display simply stops working. The problem is that when this happens,
the special driver chips on the display board can fail because sometimes
arcing can occur in the display module, which causes current spikes that
take out the driver chips. The driver chips are extremely hard to find.
Unfortunately, these display modules are quite expensive and none of the
common electronics supply places stock them. I did some research a while
back and found that the display division of Babcock (now Microsemi,
though www.babcockinc has information on them on the site) was the only
one left making these. They do list the SP-333 in their online catalog.
They do have an online quote system, but not sure what minimum quantity
might be.
If you find a source for the displays, I'd appreciate knowing where you
found them and how much they cost. I might be in the market to grab a
stash of the displays for stock for the museum, as eventually, the
museum's machines will probably lose their displays to outgassing. It's
pretty much inevitable.
Rick Bensene
The Old Calculator Museum
http://oldcalculatormuseum.com