inpermutation / hp4951b

I want to run software on my HP4951b serial protocol analyzer.

HP4951b

I want to run software on my HP4951b serial protocol analyzer.

Board layout

I am going to name these boards by their function. They appear in top-to-bottom order, when viewed from the top of the HP4951b.

TAPE

This board communicates with the tape device. It is not necessary to boot the machine, though the tape test functionality will fail, of course. (And, presumably, the actual tape functionality.)

It has a 6.000000 MHz crystal.

The board art, unfortunately, is buried under the tape header. What I can read is:

MADE #########?
REV C#########?
04951-########?

I can also see 062585 in the bottom right. There is a hand-written DB2645 on the top connector.

There is a sticker on the back that says:

04951-60020
A-2528-38

Big ICs:

• NEC D80C39C microcontroller (appears to be based on Intel MCS-48)
• National Semiconductor NSC810AN-4I RAM-IO-TIMER (incl. 1K RAM)
• 3 EPROMs: 04951-10027 12 11 85, 04951-10008 TAPE SM 1, 04951-10009 TAPE SM 2
• Motorola 1820-2232, aka MC14034BCP "8-Bit Universal Bus Register"

REMOTE

This board communicates with the REMOTE / PRINTER DE-25 (DB-25) connector on the back of the machine. It is not necessary to boot the machine, though the remote test functionality as well as the BNC video output will fail, of course. (And, presumably, the actual remote+printer functionality.)

It has a 1.8432 MHz crystal.

Big ICs:

• Motorola 1820-1779, aka MC14411P Bit Rate Generator
• Hitachi HD6350P Asynchronous Communications Interface Adapter (ACIA)

The green wire at the bottom of the photo is the BNC composite video signal.

Board Art:

04951-60017
REV A-2512-38
   MADE IN
    U.S.A.
   [(hp)]
88809F
090485

Handwritten 2645. The bus connector has a handwritten CW on it.

MEMORY

This board appears to have the program ROM and 56KB of RAM, plus the keyboard interface chip has an additional 1KB of RAM. It is necessary to boot the machine.

Big ICs:

• National Semiconductor NSC810AN-4I RAM-IO-TIMER (incl. 1K RAM)
• 4 EPROMs: 04951-10024 12 11 85, 04951-10022 12 10 85, 04951-10021 12 09 85, 04951-10023 12 10 85
• 7 x HM6264LP-15 8KB static RAM

The 16-pin keyboard connector is cable-tied to this board.

There is a NiCd battery in a plastic case. There is corrosion on the leads near this battery, so I need to remove it!

There is also a large piezo buzzer.

Board Art:

REV A-2346-38 MADE IN U.S.A.
     MEMORY BD  04951-60002

[(hp)] 88809L

There is a sticker on the back:

04951-60019
A-2528-38

The bus connector has a handwritten CW on it.

MAIN

This board is at the bottom of the case. It is underneath the CRT and contains power supply components, so I haven't removed it.

It has a 3.064 MHz crystal.

Big ICs:

• 2 EPROMs, 04951-10006 CHAR ROM 2, 04951-10005 CHAR ROM 1. TODO: dump these.
• HM6116LP-4 2KB static RAM
• HM6264LP-15 8KB static RAM
• National Semiconductor 1820-3436, aka NSC800N-4 Z80-compatible microprocessor
• Motorola SC80708P 1820-2853 aka MC68A45P Cathode Ray Tube Controller (CRTC)
• Zilog 1820-3515 aka Z8530ACS Serial Communication Controller (SCC)
• Siemens TDA 4700A Control IC for Single-Ended and Push-Pull Switched-Mode Power Supplies (SMPS)

Sticker:

04951-60018
A-2528-38

Resources

• HP Bench Briefs MAY-JUNE 1984 has an article, Replacement Parts Cross Reference, which helps you decode mystery HP part numbers (like 1820-1779) into "generic type" part numbers (like MC14411P) which you can actually find datasheets for.
• The Internet Archives' HP 4951B operating and service manual is actually for the HP 4951A, a not-identical but very similar machine.