HP-65 1333A18516 - [SOLVED] request for advice

[albertofenini]

Hi Tony, hello everyone

we fixed it !

after your suggestions and the traces we had captured, we were about to investigate
Looking for shorted, broken or cut pcb traces

we made a sketch with the cathode and anode drivers pinout on a piece
of paper, by turning the page we would have been able to see what the pinout
was when the pcb is showing the traces on the opposte side of the leds

Thank to this we immediately found out that we had did something very stupid,
as the RCD connection, probably the easiest to track down, was pointing to the wrong chip

in fact, when replacing the old drivers, we had soldered the donors swapping the
cathode and the anode chips positions

in one or two of the previous pictures it could also have be seen, the 1226 should be
on the right side (looking at the led side) while it was not

once soldered the two in the right position it started to work like a charm

before to do so, we took some pictures of the back and front of the keyboard pcb
which we are posting under a separate post, it may be of use for someone to see the traces usually
hidden under the drivers without having to remove them

We obviously did the same on the donor machine, where also we had swapped the positions,
but that didn't worked out, presumably because those original drivers were really burned

However, and this is the question for the most expert people here, is there any way to tell
which of the two drivers between cathode and anode could be not working in the possible case
that only one is faulty ?

updated pictures can be seen here : HP-65 1333A18516 - [SOLVED] request for advice