9 Aug
2014
9 Aug
'14
5:28 p.m.
On 08/09/2014 04:39 PM, Rick Bensene wrote:
Another discovery is that the tubes in the power
supply are not triodes,
and I also miscounted the pins. These are 9 (not 8) pin mini tubes, and
I was able to get a part number off of the second tube by examining it
very closely with a bright light while it was still plugged into its
socket. The tubes are 1V2 diodes. I'm not sure what they are for,
but on closer inspection of the circuit board that they plug into, there
are a number of transistors that I suspect are wired as an oscillator,
but what the diode tubes do is a mystery. The datasheet for the 1V2
tubes says they are primarily used in the flyback circuitry of
television sets, so perhaps they are used in a similar way in the HV
power supply in the calculator.
1V2 = HV rectifier diode; One of those odd tubes whose name doesn't
match its filament voltage. The 1V2 takes a 0.625V at 0.3A on the
filament, rather than the 1.4V you'd expect. The glow is very faint, so
don't expect to see it.
It sounds as if you're making real progress--congratulations!
--Chuck