I have built two EPROM programmers over the years, in order to program 2708, 2716, 2732, 2764 and finally 1702 EPROMS.
The first EPROM programmer I constructed was built in order to program 2708 and 2716 EPROMS for my Altair. The circuit is based on the magazine article “Zapper – A Computer Driven EROM Programmer” by G.H. Gable that appeared in the Decmber 1978 issue of Byte magazine. Later I also used it to program larger EPROMS for my Netronics PC. It is designed to be driven from a parallel port on my Altair — but these days I might drive it from something like an Arduino if I wanted to use it.
The power supply shown in the photograph is sufficient for programming 2708’s and provides some of the voltages for the other EPROMS, and connects via the square connector to the programmer board. The power supply is based on an old Jameco JE200 +5V supply (which supplies power for the logic) with a JE205 multi-voltage board kit to provide the -5V and +12V necessary to program a 2708 EPROM.
However, for 2716 and up and programming voltage in the 20-26v range (depending upon the EPROM) is required. The clip leads (red and black) are for connection to my lab power supply in order to provide that programming voltage. (To generate more than 20v requires that I cascade the two independent sections of my lab power supply together.)
The socket with the wired jumpers labeled “J” allows the programmer to be reconfigured for the various sorts of EPROMS.
I also note that it seems to be missing its 74121 chip, that was presumably scavenged for some other urgent need. I would need to analyze the circuit and possibly construct a suitable jumper block if I were to use this device again.
1702A EPROM Programmer
My 1702A EPROM programmer was built in order to program EPROMS for my Digital Group PC. It, too, is based on a magazine article — this time the article “Low-Cost EPROM Programmer” by Dan Vincent that appears in Popular Electronics, Feburary-March 1978.
This programmer is entirely manual. Fortunately, 1702A EPROMS have only 256 bytes, and I only needed to program a couple of them.
As with the 2708-2764 programmer, this programmer has a separate external power supply.
I also built a little reader board that I could use to verify the EPROMs by connecting the address cable from the 1702A programmer’s console and +5V.