HP 2748B bulb replacement
ard at p850ug1.demon.co.uk
Wed Oct 28 14:52:49 CDT 2009
> > My apologies for not telling the whole story.
> > ...so I bought 20 of them as a life-time
> > supply.
> Hm, how old are you?!?
They seem to be somewhat under-voltaged in the 2748 (they don't glow that
'white') so they should last a long time.
> > I haven't finished my microcontroller interface to the 2748B yet but the
> > tests in the service manual indicate that the replaced bulbs are doing
> > the job nicely.
> That belongs to a minicontroller instead a microcontroller....
Mine (a 2748A) came off an HP2100A system, but I now use it with an HP9830
'calculator'. I found the right interface on E-bay -- it's a 11202 8-bit
parallel interface with the right connector on the end of the cable.
Needless to say it works fine.
> You can just hook it up to your pc. I have a printer port "paper tape"
One minor problem is that the 2748A doesn't use TTL levels. It's a minor
problem because on the -B you have a 'TTL clamp' jumper on the interface
connector, if you fit that then you gry 5V outputs. The -A model doens't
have this., but interesting the output circuity will give TTL levels if
connected ot a TTL input terminated to +5V and ground by the appropirate
pair of reuistors (which just happen to be the ones used in the 11202)
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