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Old 18th Jun 2018, 9:37 pm   #1
jerryw22
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Join Date: Nov 2014
Location: Spalding, Lincolnshire, UK.
Posts: 40
Default Datadynamics zip-30 Teleprinter

Hi
I am in the process of restoring a datadynamics (teledynamics) ZIP-30 teleprinter.
It had over 100 faults and was in a terrible state when I got it but it is finally getting close to being fully functional.
I have a remaining problem that is proving hard to resolve.
The unit has both a paper tape punch and a reader and I have got the punch working fine but I am having a problem with the reader.
It will read single bytes at a time using the single read button but when I press the read button it just drives to the next sprocket hole and stops. It seems to be waiting for a command to read the next byte but I cannot find the fault. I have tried local and remote mode. Remote works for the printer and the punch so I know the comms are good but the reader refuses to run.
I have stripped the units and all the sensors work and the buffer amplifiers all work. I have traced all bit signals back to the processor PIA and they are all there except one. The sprocket channel has two sensors which read out of phase. The first channel reads OK and the second goes into some logic and produces a short pulse at each sprocket so I assume that this is correct. This signal gets to the PIA. Also the lights on the reader illuminate as they should and these are driven from the processor board so I know the processor is 'seeing' the correct mode. Because of the way the units are constructed it is very difficult to trace the signals any further.
Does anyone have any service data or schematics for a ZIP-30?
Or has anyone come across this issue.
Note that I have tried adjusting the amplifier gain pots for the two channels but this made no difference except to stop it working if I go too far and I know the data channels are working because the single byte read is reading correct data.
Any help would be appreciated.

Regards
Jerry
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