Introducing the HP1631D


The HP1631D is a logic analyser. It allows you to record timing and logic info on several channels simultaneously. Triggers are very flexible: You can start a timing trace efter a certain squence of bytes or vice versa. You can also load inverse assemblers that lets you decode processor mnemonics or GPIB bus info. The 1631D also has two analogue channels so that it can be used as a (limited) storage scope.

Buying one on eBay

Used units can be found on eBay starting at 50$. Make sure you get one with pods though

Technical odds and ends

Replacing the fan

The standard fan is LOUD. I replaced mine with a temperature-controlled one.The new fan is a Pabst 4312MT which has a separate NTC sensor. I located the sensor between the logic PCBs. I tested with two thermometers inside, one between the logic boards and one on the cooling fin of the PSU. The first one oscillates between 30 and 31 degrees, the second between 46,6 and 48,8 degrees.


The connectors that connect to the pods have a tendency to go awol. In that case, new flying leads can be manufactured, using crimp connectors type 44159 from Biltema. Note that these are standard automotive connectors. Most auto parts stores should stock the sleeves.

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Uploading inverse assembler files

Inverse assembler files for protocols and processors are available. Normally you would load them from a floppydrive (or HPDisk), but you can upload them via my utility by changing the start byte to XX (below). Thanks to Miguel Gullon for that tip!

Inverse assembler

Useful links

There is tons of good information available on Rudis Wiki


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