HP82915 Modem

[Joe R.]

At 07:56 PM 9/6/05 +0100, you wrote:
>> 
>> 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! :-)
>
>Ineed...
>
>> 
>> 
>>  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.

  I'll get the SM out again and tell what errors it reports. That should
give you an idea of what signals you have to provide.

   PS After I replied last time I also got out the manual for the DataComm
program. It's NO help either. The only thing interesting that I found in it
is that DataComm uses the "CPM style" block data transfer. Other names that
they give for it include XModem. Of course that's no use to you unless
you're going to run DataComm.

  Joe

>
>-tony
>