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| [93] KIM-1 resurrection! http://forum.6502.org/viewtopic.php?f=7&t=349 |
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| Author: | Ross Archer [ Sun Jan 14, 2001 8:32 pm ] |
| Post subject: | [93.1] KIM-1 resurrection! |
I have a KIM-1 I want to bring back to life, and advice is sought. Any KIM-o-philes out there? Problem #1: I applied +5 and +12, and everything came to life. Keypad has some bounces / flakiness (the "0" key is awful, PC key is dead, rest are pretty good.) Although I'd love to find a genuine replacement keypad, I figure winning the big lottery prize is more likely. I guess the best solution would be to take some loose switches and build a keyboard on a perfboard and wire to the application connector? Any other thoughts? Problem #2: Cassette interface records OK but does not load. It reads good +12 on the 311 pin 8, and the VCO out on the 565 makes a sine-wave (frequency looks to be around 80 Hz!) when idle and then goes berserk /untrackable on my scope with cassette input reading data at any volume setting above maybe 10%. The reference voltage off the 565 pin 6 isn't steady, but jumps all around when there's cassette input, same with pin 7 (error output.) I would assume U27/565 pin 6 reference *should* be rock-steady at some voltage value (whatever that would be) regardless of cassette player input, and the VCO output ought to be much, much higher in frequency. I'm pretty sure some component is dead, but as the PCB doesn't mark resistors or capacitors very well, I'm not exactly sure where to begin. P.S.: I've seen it generate square waves off the 311 when doing the PLL calibration routine. From the docs, it's supposed to be '1' or '0' logical? I tried rotating the pot and it makes absolutely no difference on my scope. I'd consider building an outboard version of the cassette interface, and run the TTL output to the clipped pin 7 of the 311, but if it's possible to repair this puppy to be stock, that would be far preferable. Ross Archer |
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