A while ago I've got an MBK-04 EPROM Box for the HP-41. The name implies that it can provide 4K ROM (1 page). As the box is nearly as large as the HP-41 this seems not be not very much. Does anybody have documentation about this EPROM box?

There are 3 EPROMs installed, from two different manufacturer, one is a TMS2764JL45. I guess such EPROMs can still be bought somewhere. Does anybody know a good source?

To burn my own ROMs I would need a suitable EPROM programmer. Hmm, don't know much about such devices. Can anybody advise me?

Any help highly appreciated!

Thank you,


Halo, Juergen;

I bought a very good programmer some months ago and I am completely satisfied. I was searching for some schematics or related information so I could build my own, but I found all I need and a bunch more with Elnec´s BeeProg+. If you want to go ahead programming other devices, I think this has one of the best cost/benefit ratio.

About the MBK-04 EPROM box: I do not know it, have never see. Any chance that you could post some pictures? Are you aware of any e-place I could find pictures as well?

Thanks and success!

Luiz (Brazil)


I don't know for sure - maybe Diego can pitch in - but I think the programmer we use for his PICs could also be used for EPROMS and is significantly cheaper. I once searched for EMPROmmers as well and I think I found one that has the EPROMS the HP-41 boxes use listed as 'can be programmed' and was btw 50-100 usd. Maybe a google with the EPROM type and EPROM programmer can lead you to similar results... Sorry, I don't have the exact info handy right now, I'm on the road...


PS: I do have the MBK box alas without any memory, but when I get home I will check on how many pages it covers.


Hi all,

Peter, the bad news are that USB PIC programmer used for Clonix and NoV's is just for PIC microcontrollers which programming procedure is way different from EPROM's.

There are plenty of EPROM (and many other devices) programmers available, and even the cheapest will make a good job for a hobbist purposes.

Googling (or "eBuy-ing") for "EPROM programmer" will show a nice bunch of'em.

My advice: get one with USB interface. :-)

Oh, please don't forget you'll also need an UV eraser if you're about to play with EPROM's.

Cheers from the Caribbean.



I should be the best source for information about it as you will still find my name on the PCB ;)

It is labled MBK 04 because it was the 4th PCB layout made by me for MBK. It can be used with EPROM-Sets from 4K to 32K. There are some informations about the setup and the EPROM-Sets on my website http://maschke.de/hp41/ under MBK-32 EPROM-Box, which was the real name of the box.

The EPROM-Sets are split into 2 upper and 8 lower bits like it was standard at that time.

More questions?


Thank you all for your fast response, and special thanks to Winfried Maschke! I didn't know about this 'secret' link on your web site. Very interesting! I will read it, and if there are still some open questions, I will come back to you ...

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