Paper Tape readers from CNC machines

Jeff G jeffg at junknet.net
Sat May 23 19:28:54 EDT 2020


So update on my end, it seems I got my tape reader (at least the reader
itself) mostly working. Turns out it was defective; had 2 bad 4049 ICs; one
had dead outputs so only 4 bits were working, the second seemed to be
noisy/flaky, so replacing both got me solid data output. So I have solid
confirmation of the strobe pins (one inverted) and the data pins.

I still don't have solid motor control, I know Duane and others mentioned
24v, but the motor sounds much happier around 15v, yet its flaky in that
while it mostly runs fine, the motor seems to not know what direction it
wants to go in. On occasion the motor doesn't want to start, and using what
I think is a reverse pin only "usually" works. I'm really half tempted to
believe this really wants 24 volts AC, but not sure I want to try that just
yet.Theres 4 diodes in the motor control section.

Theres 2, maybe 3 pins on the IDC plug, and 2 pins on the power connector
that seem to be for motor control. One seems to slow it down (although it
just stops instead, almost like a "hold", one seems to "usually" reverse
the motor, and the last seems to be a step pulse. This all sounds to me
like half the waveform it would get from a 24v AC input is missing. I
cannot find datasheets for the stepper control ICs anywhere, seems they are
Fujitsu MB14275 and MB14276.

Anyhow...since it mostly works I can see if I can actually get this thing
to read some data! Also if I can verify the motor control wiring, I'll post
up a full pinout.

BTW This is a Sanyo Denki 2401C-1 tape reader, likely from a Yasnac 2000G
CNC controlled somethin rather, likely a Mori lathe.

Jeff aka Bags


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