HP-65 1333A02242 display missing all the decimal dots

[albertofenini]

That's what I was expecting myself as well ...

We have seen :
2 volts on segment f
4 volts on segment h
6 volts on segments c, b, d, e, a
2 volts with an offset of 2 volts (.ie. waves do not start on the line of 0 volts) for segment g

We may have mixed up things, will check again this evening and let you know
take care !

(11-10-2020 01:54 PM)teenix Wrote:  

(11-10-2020 01:35 PM)albertofenini Wrote:  I got it now ...
the value we should look for is not between the PIN 18 (h segment) and the PIN 11 (Vbsw) of the Anode driver
instead between the 3rd pin and the 5th pin of the left coil "chip"

I thought you meant that something INSIDE the anode driver about the h segment was open and not driving current to the decimal point ...

Is the waveform for that segment good then ?

I'm asking because the display was showing some 0s, in a 0 the g segment is obviously off,
so we were expecting a flat line as waveform for that segment, while in reality it was not flat ...

Thanks again !

Electrically wise, same points.

Yes, there could indeed be a fault inside the anode driver. Hopefully testing the coil, solder connections and PCB traces for the decimal point will confirm this or a fault on the board.

From your wave forms for 0.00 I would expect the same activity on segments a b c d e f, with no activity on g except for noise. Segment h (I would expect) should have similar activity to the g segment but, with a higher pulse once per display refresh indicating the decimal point. I cannot say for sure without being home to test myself.

cheers

Tony