As I write, I finally found the 75152. It's a dual line receiver and I have a pinout in an old data book. Reverse engineering proved that this 75152 was not in the same circuit, although many lines from the "What was it?" 75188 went under it to a neaby, carefully hidden 75189.
I popped in a MC 1488 and MC1489 from the bits bags and I'm off to try it. Thanks to all for the help
Here I am back again. It didn't communicate. Examination revealed I had a 5V, +14.5V and nothing on the -12V or whatever. I found an orange glass thing (?diode? Like a 1N914 except the orange bit is longer and no cathode mark) with no markings also smoked and blown away. The positioning of the other power pins leads nme to thinK it's the -12V/-15V. Tracks are blown, and I'll have to find where they went. The -12V appears to be for comms only
We have also lost the stored memory, despite a backup battery.That frees me up to do some real testing.
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With Best Regards,
Declan Moriarty -- Author: Declan Moriarty INET: [EMAIL PROTECTED]
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