[DECtec] [HECnet] RX50 schematics?

[Peter Coghlan]

Evening,

Do RX50 schematics exist on bitsavers, fiche, or elsewhere?   I have one 
here and it doesn't appear to work.   Testing is showing either a busted 
motor or something wrong in the voltage control stuff.

Thanks!



Oops.   Just found 'em up on bitsavers.   Let's hope it's helpful with test 
point values.   I have no idea if TP1 should be 2.4008VDC or it should be a 
specific waveform.


I took a look at the schematics.   Something around 2.5VDC looks reasonable
for TP1 when nothing much is happening, because of the potential divider
formed by R2 and R3.

I guess you have already checked that the motor is free to turn?

It looks like the motor is probably connected between J11 pins 3 and 4.   Do
you have more than a few volts DC between those pins?

It looks MPWR (connector J4 pin 3) is the signal to tell the motor to run.
You should have something over 0.7VDC here for the motor to run.

What have you got at TP4 - you would need a few volts here too.

What about TP5? It should be 0V when the motor is stopped and a small DC
voltage when it is running.   If there is more than half a volt or so here,
check whether R15 is hot.

Regards,
Peter Coghlan.

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