HP-65 1333A02242 display missing all the decimal dots

[albertofenini]

Thanks Tony, will try this evening and will post ...
Can we take these values and these waves from the logic board connector as well ?
I think it may be easier since the Hybrid does not have pins connections accessible from the top ....

(11-09-2020 03:06 AM)teenix Wrote:  

(11-08-2020 11:39 PM)albertofenini Wrote:  Hi everyone
this is a more challenging work ...
The unit is working in the meaning that it turns on but all of the decimal dots are missing
We have given the unit a good clean and thinking of a cold joint on the pin that control
the decimal dot anode segment (I believe is the h segment)
we have refreshed that soldered pin of the 1820-1029 anode driver
However it didn't fix the problem
What could we possibly check to troubleshoot the problem ?
Thanks in advance for any idea you may want to share with us
Take care !!
HP-65 1333A02242 display missing all the decimal dots

I would check that the decimal point data is being generated with an oscilloscope and exits from the hybrid chip pins 11 to 15 and that they appear on the anode driver pins 1 to 5.

Page 9 of my Classic Notes PDF show the waveforms for 0.00 being displayed.

http://teenix.org/ClassicNotes.pdf

If they are appearing correctly then perhaps the anode driver is faulty as it decodes these signals to provide the digits and decimal point.

I would also check that the correct signals are appearing from pin 18 from the anode driver for the decimal point. Perhaps the corresponding coil is open circuit or has a bad connection.

cheers

Tony