UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Studer / Revox etc BiPolar PROMS! Question and concerns!

ricard · 23rd May 2020, 4:45 am

I've got some thoughts on the subject although have never actually tried this so it's academic at best. I do have a bit of experience with EPROMs, having used them not only for data storage but also for function mapping in the same way that they are used in certain tape recorders.

Although bipolar PROMs are rare as are the programmers that program them, I'm thinking that it should be possible to replace them, electrically at least, with slightly more modern UV erasable EPROMs (such as the 2716), EEPROMs (Electrcially Erasable PROMs) (such as the 2816), or even Flash (electrically erasable) ROMs.Programmers for these types of chips are still readily available, as EPROM technology was popular in microcomputer systems, so many hobbyists would have had an EPROM programmer for their own projects. In fact, I think it's still possible to buy USB EPROM programmers new today. In contrast, bipolar PROMs would have been used mostly in an industrial context.

A ROM basically is a map from one set of binary values (the address) to another (the data), and the underlying technology is not important, especially in a tape recorder where the access time (which is usually faster for bipolar PROMs than for EPROMs) is not critical.

The disadvantage when using EPROMs is that they are usually physically larger devices (24, 28 and 32 pin devices in 0.6" wide body packages, rather than the typically 16 pin 0.3" wide body packages typically used for bipolar EPROMs), being able to hold much more data - a typical bipolar PROM has 8 address lines (256 addresses) whereas the smallest modern EPROM which uses 5V-only supplies is the 2716 which has 2048 addresses). So some form of adapter needs to be devised. I'm thinking of something along the lines of a 16 pin header which plugs into the socket where the PROM was mounted, emanating at an adapter board on which the EPROM is socketted.

The difference in memory size isn't a problem per se, it's just a question of programming the relevant part of the memory chip, and connecting the unused address lines to 0V.

Well, at least some thoughts on the subject.

23rd May 2020, 4:45 am	#2
ricard Octode Join Date: Mar 2006 Location: Lund, Sweden Posts: 1,632	Re: Studer / Revox etc BiPolar PROMS! Question and concerns! I've got some thoughts on the subject although have never actually tried this so it's academic at best. I do have a bit of experience with EPROMs, having used them not only for data storage but also for function mapping in the same way that they are used in certain tape recorders. Although bipolar PROMs are rare as are the programmers that program them, I'm thinking that it should be possible to replace them, electrically at least, with slightly more modern UV erasable EPROMs (such as the 2716), EEPROMs (Electrcially Erasable PROMs) (such as the 2816), or even Flash (electrically erasable) ROMs.Programmers for these types of chips are still readily available, as EPROM technology was popular in microcomputer systems, so many hobbyists would have had an EPROM programmer for their own projects. In fact, I think it's still possible to buy USB EPROM programmers new today. In contrast, bipolar PROMs would have been used mostly in an industrial context. A ROM basically is a map from one set of binary values (the address) to another (the data), and the underlying technology is not important, especially in a tape recorder where the access time (which is usually faster for bipolar PROMs than for EPROMs) is not critical. The disadvantage when using EPROMs is that they are usually physically larger devices (24, 28 and 32 pin devices in 0.6" wide body packages, rather than the typically 16 pin 0.3" wide body packages typically used for bipolar EPROMs), being able to hold much more data - a typical bipolar PROM has 8 address lines (256 addresses) whereas the smallest modern EPROM which uses 5V-only supplies is the 2716 which has 2048 addresses). So some form of adapter needs to be devised. I'm thinking of something along the lines of a 16 pin header which plugs into the socket where the PROM was mounted, emanating at an adapter board on which the EPROM is socketted. The difference in memory size isn't a problem per se, it's just a question of programming the relevant part of the memory chip, and connecting the unused address lines to 0V. Well, at least some thoughts on the subject.