UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - A Simple Programmer for TESLA "MH74S-" bipolar PROMs

SiriusHardware · 5th Oct 2019, 3:43 pm

circuitryboy, thank you for sharing this, especially the 'light bulb' revelation that the Texas PROMS may use a near identical algorithm to the Texas bipolar PROM devices (or possibly the other way around), even though there does not seem to have been an exact 'SN' variant of the 571 device.

The approach of using an MK14 to be the controller is satisfyingly hardcore, but there is one minor snag with that - a lot of people wanting to program these PROMs are trying to get their first MK14 replica (or maybe a non-working original MK14) working, so this creates a catch-22 situation where their PROM programmer can't be used until they have a set of programmed MK14 OS PROMs with which to get the MK14 running.

One way around this paradox would be to program an EPROM with the MK14 OS and make a temporary EPROM-to-two-Proms adaptor with the pins from the EPROM routed to the appropriate IC2 and IC3 socket pins - you could get the MK14 up and running like that and then use it to program a pair of Tesla MK14 OS PROMs for itself. However, this assumes ownership of an EPROM programmer, which not everyone has.

As an alternative, I would also be interested to see your hardware approach married to a cheap, widely available microcontroller like an Arduino. I'm not currently in a position to try this out myself as I don't have any of the Tesla PROMs but I am sure that at least two forum members here do have quite a few of these ICs between them, so hopefully they'll give it a test drive.

I'd be interested to know what sort of programming pass / fail success rate you've had so far, I have read comments to the effect that these MH devices can be a bit temperamental and un-cooperative.

5th Oct 2019, 3:43 pm	#6
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,556	Re: A Simple Programmer for TESLA "MH74S-" bipolar PROMs circuitryboy, thank you for sharing this, especially the 'light bulb' revelation that the Texas PROMS may use a near identical algorithm to the Texas bipolar PROM devices (or possibly the other way around), even though there does not seem to have been an exact 'SN' variant of the 571 device. The approach of using an MK14 to be the controller is satisfyingly hardcore, but there is one minor snag with that - a lot of people wanting to program these PROMs are trying to get their first MK14 replica (or maybe a non-working original MK14) working, so this creates a catch-22 situation where their PROM programmer can't be used until they have a set of programmed MK14 OS PROMs with which to get the MK14 running. One way around this paradox would be to program an EPROM with the MK14 OS and make a temporary EPROM-to-two-Proms adaptor with the pins from the EPROM routed to the appropriate IC2 and IC3 socket pins - you could get the MK14 up and running like that and then use it to program a pair of Tesla MK14 OS PROMs for itself. However, this assumes ownership of an EPROM programmer, which not everyone has. As an alternative, I would also be interested to see your hardware approach married to a cheap, widely available microcontroller like an Arduino. I'm not currently in a position to try this out myself as I don't have any of the Tesla PROMs but I am sure that at least two forum members here do have quite a few of these ICs between them, so hopefully they'll give it a test drive. I'd be interested to know what sort of programming pass / fail success rate you've had so far, I have read comments to the effect that these MH devices can be a bit temperamental and un-cooperative.