ard at p850ug1.demon.co.uk
Tue Sep 6 13:56:15 CDT 2005
> At 10:18 PM 9/5/05 +0100, you wrote:
> >I recently won an HP82915 Modem on E-bay (my first, and so far, only
> >purchase there).
> Tony? E-bay?? Now I know the end of the world is coming! :-)
> I was suprised to get it for the opening bid, I though
> >I'd have at least one other HP collector to contend with. It is, you see,
> >the internal modem for the HP Integral.
> Darn you! I keep a constant watch on E-bay for Integral stuff but I
> didn't see it!
Lucky me :-)
It wasn't listed as an Integral part, only as an HP82915 Modem. I was
pretty sure that was the Integral modem, one of my manuals mentions it in
passing. When it came, I was certain. Right size board, right connector
(a DIN 41612 socket), plastic cover over the solder side, etc.
> >Anyway, it's a single PCB that fits into one of the Integral's expansion
> >slots. Cotnains about 20 ICs, most of which I recognise. One odd thing is
> >that the serial chip used is an 8250, a somewhat odd choice for a
> >68000-based machine.
> >Does anyone here know anything about using it?
> Not much. It's a 300/1200 Baud modem. ONE sales brochure list it in ONE
> place but give NO details or pictures and never mentions it again. The
it's not that interesting to look at. It looks like any other Integral
PCB. As I said, about 17 chips, a crystel, a crystal oscillator, a 3
terminal regualtro, a transformer, a reed relay, a transistor, and some
passives. 2 US-style phone sockets on the bracket, both unmarked (may
just be wired pin-pin, with the appropirate pair of pins also going to
the modem circuitry).
> service manuals don't give ANY details about it. (It's one of those "If it
> fails, replace the CCA. If it still fails, replace the whole thing."
Repairing it would probably violate the FCC approval (it would certainly
violate BT appoval for a UK modem). Since I don't intend to connect this
to a public phone line, that doesn't bother me.
That said, the HP Portable Plus service manual (I have it) does give some
repair procedures and a scheamtic for its internal modem (totally
different ot the IPC one, BTW). I does say that certain components
(mostly resistors) must not be replaced in the field, since this could
affect the FCC approval (incorrect transmitter level, etc).
> procedures.) To test it they have you install two modems in the IPC and
> plug them into separate phone lines and call one from the other while
> running the diagnostics program. The diagnostics program will report No
> Carrier, No Dialtone and the like but that's all. There no mention of a
> null-modem type cable.
Well, there won't be any form of null modem cable. There are only 2 wires
to the telephone line, and polarity shouldn't matter. However, we had a
brief discussion here a few weeks ago about linking 2 modems without the
use of a public telephone system, e.g. by buying a small telephone
exchange. I am wondering how much is actually needed for _this_ modem.
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