jcp@BRL-TGR.ARPA (06/30/84)
From: Joe Pistritto <jcp@BRL-TGR.ARPA> Folks: I just bought the serial/parallel interface converter for the Okidata 93, installed it correctly, and GUESS WHAT? The signal ground line (pin 7), has ~20V of AC on it. (The board does pass its diagnostic and the printer is real happy. Connect it to a VT-100 though, which connects pin 1 & 7 to chassis ground, and the internal circuit breaker pops in about 5 seconds though) I believe this is due to the fact that they probably split 48V internally to make -24 and +24 to drive the RS-232. I suspect its a 'feature', which means this device needs to be 'isolated' from other RS-232 devices. I intend to send the interface back, and buy an external RS-232 to Centronics interface converter, and am wondering which one to get: The two I know about are: The Black Box 'Mini Print Spooler' B-PIA90, which is $306 The Quadram 'Microfazer' 8K QD-MF-SP-8, available from The Bottom Line for $149 Does anyone have experience with these, or have any better suggestions? (I need to convert the interface to RS-232, but really don't need much buffering, as I am limited to 1200 baud anyway) -JCP-
CSTROM@SIMTEL20.ARPA (07/01/84)
Two comments - shame on DEC for connecting pins 7 and 20 internally. I agree that 20V on a pin that is supposed to be at ground is not very friendly, but specifications for the RS-232 interface specifically spell out pins 1 and 7 as being separate. Enough soap box activiity for today... I have a serial to parallel converter manufactured by Engineering Specialties, Inc. They also make a parallel to serial converter. The unit is CMOS (you need 5V at < 20ma which I stole from my buffer box) and the beast runs quite reliably at 19.2K. Price is < $100. Check any Byte for their small ad in the back of the magazine.
mlsmith@NADC.ARPA (07/09/84)
Recommend you look at the Angel buffer too. About the same as the Microfazer,so lower price (I don't have a current one for the Angel) could be the determiner. mlsmith@NADC.ARPA