HP 85 stuff

From: Geoff Roberts <geoffrob_at_stmarks.pp.catholic.edu.au>
Date: Mon Jul 3 20:48:37 2000

----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <classiccmp_at_classiccmp.org>
Sent: Tuesday, July 04, 2000 3:40 AM
Subject: Re: HP 85 stuff

> > > 2) Any software about?
> >
> > Yes. lots but none is posted on the web that I know of. Beware
that the
> > HP cassettes are very prone to broken belts and shedding their media
> > original tapes may not be usable.

Ok, I'll keep that in mind. I'm going to try and track down some NOS,
bound to be a fair bit floating around.

> HP85s with an HPIB interface and a mass storage ROM (IIRC) can support
> floppy drives. If you have this sort of set-up, it's worth copying any
> tapes you find onto floppies.

No, I don't have any of the addons for the machine, I'll be looking for
them now that I know what to look for.

> > >First HP I've been able to find, nice little machine....
> >
> > Yes, they are but they have two problems. The "rubber" feed
wheel on
> > the tape drive turns to goo

I'm going to pull the thing down and check that. Copyed a prev msg about
a replacement. Whatever works.

> > and the two belts that operate the printer wear
> > out. You can test the printer by pressing the "TEST" button. It
> > display and print the full character set.

Printer seems ok.

> I've only ever once had an electronic fault on one. This was a shorted
> capacitor on the PSU/printer driver board (the vertical one to the
> of the printer assembly), and it caused at least one of the PSU
> to be missing.

Ok, I'll keep it in mind if it ever plays up.

> This board can be run disconnected from the rest of the machine (just
> connect the input from the mains transformer). Also, the custom 40 pin
> printer control chip is socketed on most machines, and can be removed
> stored in conductive foam. This lets you work on the PSU with little
> to anything you can't replace if you make a mistake.

sounds good.

> FWIW, much of the logic in the HP85 runs at 6V (not a typo).


> custom interface IC that links to the processor bus and lets you hang
> conventional 5V microcontroller-based interface off the other side.
> Information on this seems to be hard to find, although the HP-IL
> interface user manual includes a schematic of that interface, with
> pinouts of the bus and the bus translator chip.

Hmmm, that has possibilities.. I am also lead to believe the 85 can
talk to various pieces of HP test equipment, and that they share a
common bus. (With the right interface of course).

> Oh, one last thing. If you want to take the top off, first pull off
> eject button from the tape drive. Then undo the screws on the bottom,
> lift the casing off. If you don't remove the eject button first,
> have problems getting the case to come free.

Ok, thanks for that. Often the worst part of fixing (ptbl tv for
instance) is not the fault, but getting the case either on, off or both.
With some stuff it's like getting an egg back into it's shell.


Geoff Roberts
Computer Systems Manager
Saint Mark's College
Port Pirie,
South Australia
ICQ: 1970476
Received on Mon Jul 03 2000 - 20:48:37 BST

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