HP9810A alive again!

[tony duell]

> 
> After replacing a lot of dead National Semiconductor TTL ICs this nice
> little machine from 1972-1973 is running again. It works perfectly to do
> calculations and also to create programs. I also managed to both store and
> restore a program written onto a home made magnetic card. Home made since I
> wasn't able to find any.

How did you make the card? I have a few original ones for my 9810 and 9820, but only
a few. So a way to make more would be interesting.

> There are a few issues left: The belt in the card reader is slipping a bit
> so a replacement would probably be needed to get it working 100%. One

It's actually a standard O-ring, as mentioned in my repair notes. Size BS231 -- 2+7/8" OD, 2+5/8" ID, 
1/8" thick. The only problem I had was the minimum order quantity was 50 or something. Yes, I do have
plenty of them around -- but packed in one of about 700 boxes from the house move.

> segment in the display is dead.

That, alas, I think you have to live with.

-tony