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Feb 11 2015

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About 15 years ago I purchased five rack mount cases with some manuals for $100. What I had was two HP 5420A Digital Signal Analyzers, minus a 5443A Control Unit (computer), one software tape and half the service manuals. Initially not knowing much about this equipment I set about reading the manual I had to familiarize myself with the equipment so I could set about firing it up. Apart from some initial cleaning I had to make up a 50 way interconnection (MIOB) cable which connects the 5440B, 5443A, and 5441A. The 5440B Plugin Mainframe houses the 54410A A/D Converter, and the 54470B Digital Filter. The 5443A Keyboard/Control Unit is the main processor for the system with some of the operator push buttons. Finally, the 5441A Display is the main part of the user interface comprising, the rest of the keyboard, the video display (both text and graphics) and the tape interface to allow storage and retrival of both system software and data.

After getting everything ready I decided to try and boot the system. Placed tape into a drive and powered up. This is were I learned a hard lesson, the capstan drive wheel in the tape drive had turned to goo and proceeded to mash my one and only tape. F$#k!!

At the time there was not much information on the web about this equipment and other people were searching for tapes apprantly with no luck. However, I decided to keep the equipment in case I ever managed to find any tapes. As the years went by I managed to collect more information as HP Journals were made available online. I also acquired a complete set of manuals for both the HP 5420A Digital Signal Analyzer and the HP 5423A Digital Structural Analyzer. Along the way I found out that the CPU in the 5443A was infact an HP 21MX and the was a wealth of information online about this computer.

In 2012 I decided to make a serious attempt at getting this equipment working. The plan was try and find to viable tapes, build a hardware interface to a PC, repair the equipment so that tapes can be read, read tapes and transfer the software to the PC for safe storage, upload software back into the 5420 to ensure the code still functions. Finally, make a new memory card which includes flash memory to store the system software.

In early 2013 after building a front panel interface for the 21MX CPU with a USB connection for modern PCs I got side tracked by trying to use the tape drive from an HP85 to read the 5420/23 tapes I spent too much time on this fruitless exercise and then due to other pressures like work and family I didn't get back to this project till late 2014. As of 11 Feb 2015 I have the equipment working with HP5420B software, that code is saved on a few PCs and memory sticks, and most importantly I can boot the 5420 without using a tape!

You may ask, "Why bother with a big old technology boat anchor?"

There are many reasons:

2016/2017 is coming soon making these systems 40 years old.

The equipment was used in testing of components of the Space Shuttle.

I don't want to see good quality equipment go to land fill.

I wanted to see how it was possible squeeze so much performance out of a computer this old.

Most important of all I wanted to keep this equipment running for the talented engineers who designed the hardware and software.


The contents of these pages to the best of my knowledge are factual but if you find something that is incorrect, or have more accurate or some new information please contact me.

EMAIL: peter@oneillassociates.com.au