ellindsey Posted May 26, 2022 Share Posted May 26, 2022 Several decades ago, I was exploring a junkyard where I found a pile of industrial-looking circuit boards in a pile of scrap, and on a whim bought some of them for a few dollars. They've been in my parts bin ever since. Lately I've decided to try and research what these actually were, in case they were ever anything interesting. There are two different types, one which appears to be a CPU board, and one which is a keyboard and display board. I'm pretty sure they used to be connected with the ribbon cables which are now cut off. The CPU board has a TMS9995 CPU (in the lower left, with the text nearly unreadable), two TMS9901 interface chips, three sockets for EPROMS, a pair of N82LS135N PROMs, a pair of ICM7218 7 segment display drivers, a DS1220 battery-backed SRAM, a fair number of optoisolators, and various glue logic chips. The display board has a 16 button membrane keyboard, and a lot of 7 segment LED displays. It also has multiple voltage regulators on heatsinks on the other side of the board. On one of the controller boards, the EPROMS have labels that say "PSE&G". PSE&G is one of our local energy utilities companies, which suggests that these boards were probably part of some energy monitoring or distribution system. The only other label I can find on these is here on the back side of the display boards. Megatran Industries is a local electronics manufacturing company who make custom systems for the power industry and has been around since 1968, so that's probably who made these boards. That's about as far as I've gotten with these. If I feel really ambitious I might try and trace out some of the circuitry and connections between the board to confirm that these actually went together. I really doubt that any of the components on here are salvageable, it's all pretty badly corroded from being stored outdoors in a junkyard before I found them. My wife and I are trying to de-clutter the condo and get rid of anything we don't use, so these will probably end up going on the free table at the next local vintage computer swap meet. 5 1 Quote Link to comment Share on other sites More sharing options...
HOME AUTOMATION Posted May 27, 2022 Share Posted May 27, 2022 EPROM DUMP? Quote Link to comment Share on other sites More sharing options...
WhataKowinkydink Posted May 27, 2022 Share Posted May 27, 2022 If memory serves wasn't the TMS9900 designed for mini computers? That in mind these all look to me like they're out of some TI-brand minicomputer. Quote Link to comment Share on other sites More sharing options...
+pixelpedant Posted May 27, 2022 Share Posted May 27, 2022 It was originally implemented in TI's minicomputers, yes, but that is not what this is. As far as third party industrial use goes, the TMS9900 was never a top dog, but it does show up here and there. Examples of use in military and aerospace contexts have come up here, now and again, for example. Anyway, cool mystery hardware, there! So thank you for sharing! 3 1 Quote Link to comment Share on other sites More sharing options...
wierd_w Posted May 27, 2022 Share Posted May 27, 2022 Those are hand-traced traces on those PCBs. You hardly ever see that these days. 1 Quote Link to comment Share on other sites More sharing options...
Willsy Posted May 27, 2022 Share Posted May 27, 2022 Looks like an industrial controller/PLC type system to me. Quote Link to comment Share on other sites More sharing options...
+FarmerPotato Posted June 1, 2022 Share Posted June 1, 2022 @ellindsey I would love to examine those, dump the EPROMS, etc. First and most important, whether the EPROMs contain any TI real-time exec, libraries, or if it was all custom. I bet the EPROMs are ok, though I see lots of broken copper traces. This year I’ve started collecting 9900 boards and studying the layout. To improve my own. 1 Quote Link to comment Share on other sites More sharing options...
ellindsey Posted June 1, 2022 Author Share Posted June 1, 2022 39 minutes ago, FarmerPotato said: @ellindsey I would love to examine those, dump the EPROMS, etc. First and most important, whether the EPROMs contain any TI real-time exec, libraries, or if it was all custom. I bet the EPROMs are ok, though I see lots of broken copper traces. This year I’ve started collecting 9900 boards and studying the layout. To improve my own. Unfortunately, I don't have any access to a EPROM reader at the moment. I'll have to find someone at our local hackerspace or vintage computer meetup who has one that can read these. 1 Quote Link to comment Share on other sites More sharing options...
+FarmerPotato Posted June 2, 2022 Share Posted June 2, 2022 The keypad is very much like the present Grayhill 88BB model. With custom overlay. I think the key names point to a PLC. With primary functions Select, Step, Repeat, Seq. You might use those to edit steps of a program, in NVRAM, with instructions to monitor inputs, set outputs, handle interrupts, trigger alarms, etc. Im not familiar with PLCs - but for example Google manuals for programming “ladder logic”. TI made 9900 based PLCs in Johnson City, until that business was sold to Siemens. (Simatic). I think they had already upgraded to 68000. I suggest “# OF RAPS” could mean Remote Area Power Supply. (Got around the hip hop google hits.) 3 Quote Link to comment Share on other sites More sharing options...
apersson850 Posted June 14, 2022 Share Posted June 14, 2022 It doesn't look like a "typical" PLC, if there ever was one. But then TI made some that were a bit odd, so maybe. Quote Link to comment Share on other sites More sharing options...
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