Hamurabi Focal source

Tony Duell ard at p850ug1.demon.co.uk
Wed Mar 31 13:26:21 CDT 2010

> If you get stuck, I can sure help.  I recently restored an HP 2748B
> optical reader (500 CPS) and built an RS232 interface for it so that

I restored one of thoise a couple of years back -- or actually the -A 
version which has simpler electronics (but much the same functionality). 
I got the HP9800 interface for it (HP11202 Opt A01 IIRC) on E-bay. As you 
probably know the outputs of the 2748 are pilled up to 12V, but through 
10k resisotrs, whcih means they will feed the 180R/390R-terminated TTL 
inputs of the 11202 with no prolems. Of course the -B model that you have 
has clamp diodes anyway so you can force the outputs to TTL levels by 
jumpering 2 pins on the connector.

What was wrong with yous? Mine had a bad mbearing in the magnetic clutch. 
T oreplace that I had to make special tools to press the clutch unit 
aprt and put it togetehr again. The ball race itself was a standard size 
and I had no problems getting one. Of course I also had to make the 
alignment mandrel to ge the clutch parts centred up wehn I put the motor 
unit back on. 

There are a few photos in my flickr account (tony_duell) of the internals 
of the read head and of taking the motor/clutch apart.


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