I own a HP Portable plus, so this may not all apply to a 110. I hope I will get a 110 soon.
You need a power adapter HP82059D (in the U.S) for the RCH port, i believe. I am from Europe, so I have a HP82066B. This should be rather easy to obtain.
The adapter says:
Input 90-120 VAC 50-60Hz 7VA
Output 8VAC 3VA max
It's a simple transformer, so there should be no problem finding a replacement. The plug could be a problem, but I believe you'll surely know some tricks, when you're doing packet radio
The DB9 port is a serial port with a stange nonstandard pinning. I'll post it at the end of this article.
The IN and OUT ports are for so-called HPIL peripherals. This is not the place to discuss all of them, but there were a HPIL Printer (Thinkjet, 2225B) and a Disk Station (9114 or the second revision: 9114B)
There were also some interface converters to RS232, HPIB, GPIO,
Sorry no, there was never an upgrade for the DOS.
Here the plan for a homebuilt cable directly from my HPPP (portable plus) manual:
HP name serial 25 pin(modem) 1 DTR -> 20
2 TxD -> 2
3 RxD 4
5 CTS <- 5
6 DSR <- 6
7 GND -- 7
8 DCD <- 8
9 RING <- 22
Have fun with it. This is a really cute machine. I might have some software for it (a special implementation of Kermit) and an editor.
No, the machine is not fully PC compatible, the serial ports should be accessed with the DOS/BIOS functions.
cuagn
Reinhard