[GreenKeys] M33/32 AC Receive Loop

[Jon Penner]

Hi John,

I'm having similar problems with my M32. 

Works great on local (buttons and everything). 

When I reverse the external loop, the motor shuts off like it's supposed too.

Forward loop turns the motor on but machine runs open.

When I'm in local and Forward external loop current happens, buzzer sounds for 2 seconds and then goes online, again with no selector magnet hold.

When "online" and running open, turning the dial causes it to go local and hold the magnets.

So everything works as the book says, except the selector magnets holding on a forward external loop connection.

Currently tracing and highlighting schematic to see where the missing link is. 

73

-Jon

N5MHI

 

John Ball ball.of.john at gmail.com 
Tue Feb 4 01:28:13 EST 2014 



My teletype and UCC6 functions fine in Local but in Line it's the opposite.
I have a serial 20ma current loop adapter which uses 4100 and 4200
optocouplers and I could not get the machine to both stop marking or
transmit anything to the adapter when wired up. For testing I put it in half
duplex mode and bridged terminals 6 and 7 which caused the selector magnet
to energize and idle the machine. When I checked the voltage at the same
terminals I saw it was reading -0.5v DC and 6.6v AC. I understand the send
loop is AC but isn't the receive loop DC? I've looked at all the diodes on
the circuit card without desoldering them and none were obviously blown or
shorted. Is it worth it to pull them off and check anyways or should I be
looking elsewhere? I did have CR1 short out about a month ago for no obvious
reason. I replaced it and CR2 with matched values.

-John

 		 	   		  
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