HP-65 1333A02242 display missing all the decimal dots

[teenix]

To which attached image are you referring ?

It should be at bottom of last post.

CLx just clears the display and allows a new number entry, then pressing the DP button should result in just the decimal point showing.

You meant the 18th pin right ?
My applogies, yes.

We are in difficulties comparing our waveforms with yours and understand if ours are correct or not. What scale for the time and volt you suggest ?

For viewing a full display refresh, 2V per Div and say 40uS per div should be ok, triggered on the RCD pulse if you can, so you can see everything in a display refresh.

You say that we should see 15 pulses ... in the STEP image we uploaded we see 4 square waves and noise in between
The first square wave is a little more distant of the following three, is this what you mean ?
Four is because 0.00 in theory is 4 digit ? (the 3 zeroes and the digital point ?)
Should we lit all the display digits to see the 15 pulses ?

I was pretty sure that all 15 pulses should be there regardless of how many digits are being displayed. Have a look at page 15 of the Classic Notes, it shows a HP-65 waveform.

(The DP coil might be open circuit as well.)
Any way we can check that too ?
From the common coil terminal to the DP coil terminal should measure low ohms. I think this should be between VBsw and pin 18 of the anode driver. VBsw is the switched side of the battery, 12th pin in from right of cpu to keyboard connector

cheers

Tony