HP-75 EPROM programmer

Just noticed a device that looks like an HP-75 EPROM programmer on tas. look at auction 300542525954 . I have two EPROMs for sale if someone buys it!


Darn seller says he will not ship to Canada, and is not available to answer questions. I am looking for just this kind of thing for a 75.


Sounds like something two enterprising individuals on MoHPC might engage in to bypass (so to speak) the TAS's seller's objection to sending goods to our friends to the North.


If it comes to that I would certainly appreciate assistance getting this item. I will keep on trying to contact the seller.

If I where to get it would be happy to reverse engineer it and share a schematic with anyone who was interested. The EPROMs on it look like 2532s which are a non-standard pinout 4K eprom made by TI among others.


If you need a US shipping address, drop me an email.



There does not appear to be any circuitry to either generate or switch a programming voltage. I suspect that it is a module emulator. HP did their firmware development on various "big" computers, and used commercially available EPROM programmers, so they would have been unlikely to develop their own EPROM programmer specifically for the HP-75.

Based on the number of EPROMs and sockets, it looks like probably emulates the mainframe ROMs in addition to plug-in ROMs. If so, and unless that mainframe ROM emulation can be disabled, it won't be useful with a normal HP-75.

Relatively late in the HP-75 product life, HP introduced the 82713A Plugin Module Simulator, which would be far more useful to a user or developer than this device which was intended for internal HP use.



I recognize the seller handle, I have bought from him before. His name is Bruce Larribee, and I found him to be an extremely helpful guy. From what I know about Bruce, the lack of shipping to Canada is probably just an oversight, as he had the same limitation on shipping to Australia at one point, but he was more than happy to ship here. Bruce is an ebay newbie, so it's probably just a matter of someone in the US or Australia contacting Bruce and asking him to modify the auction etc.

Let me know if you want me to contact him on your behalf.



Thanks I think its probably an oversight too. I tried to bid but I got a message saying that seller restriction prevent me from bidding.

If you would contact the seller on my behalf, I would certainly appreciate it.

Edited: 1 Apr 2011, 7:11 a.m.


I also noted that there does not seem to be any facility to program EPROMs onboard, but that is not an issue for me have have enough EPROM programmers, evn some that can handle old obsolete type like 2532.

It occurred to me too that they may have been a code development jig for the 75, 10 regular sockets would be 40K and the 4 ZIFs would be another 16K.

Yes I have heard of the 82713A but they seem to be in very short supply, and you may be right that this item may not be of a lot of use, but I think at the very least it would be interesting.


I suspect this was the development board that sat outside the prototype HP-75 back when they were still writing the code for it. I had a proto-75 for a while in the early 1980s for use in evaluating the still-being-defined HP-IL in the spectrum analyzers and modular measurement systems (HP70000 series) being designed in their instrumentation group.

One item that made that fun was that I received the proto-75 the same weekend I drove up to Corvallis for a big PPC (HHC) conference there. Needless to say, I had to make sure the trunk of my Scirocco was kept closed when other HP user friends were around lest they see the much-rumored but not-yet-announced 75...

Current design tools - with high quality simulation, TCP/IP, and flash memory in real devices - sure are better than what we had back then!!

No, I don't have that '75 - it went back to Corvallis once HP-IL was defined (and I bought my own '75).


If you can't find a HP-75 Eprom emulator, you may be able to make one fairly easily using the tech manual for it. It should be available either from the Museum or from Jake Schwartz. I believe I sent him my manual set many years ago for inclusion in CD-ROMs (including the '41s dedicated printer and various others).

Using a modern CPLD or FPGA the entire emulator could probably be built inside a '75 module or even into the '75 itself, including more flash memory than the entire '75 software universe could fill.

Jim (with many fond memories of my '75, long gone)

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