Viking SCSI controller RS232 adapter

Douglas Taylor dj.taylor4 at
Thu Jun 30 17:07:34 CDT 2022

On 6/30/2022 4:05 PM, Glen Slick via cctalk wrote:
> On Thu, Jun 30, 2022, 12:34 PM Douglas Taylor via cctalk <
> cctalk at> wrote:
>> Update -  I have 3 of these Viking controllers, 2 are rebadged to
>> Alphatronix.
>> 1. I was able to 'kludge' together jumpers to connect a laptop serial
>> port to the controller.  Pin 20 IDC -> pin 2 DB-9, pin 22 IDC -> pin 3
>> DB-9 and pin 24 or 25 IDC -> pin 5 DB-9.  It didn't seem to matter if
>> you used 24 or 25 for the ground.
> Did you split off the connections to Pin 20 and Pin 22 of the controller so
> that they only connected to the serial port, and not to the SCSI bus, or
> were they wired in parallel to both the serial port and the SCSI bus?

You're quite right.  I didn't isolate those signals from the SCSI bus.  
That's what that adapter does, I'm sure.

Come to think of it, I can access drives connected to the controller as 
long as the RS232 pins are left floating.  One of those lines does 
something that I'm not aware of.  A search tells me that pin 20 is a 
ground on the SCSI bus, 22 and 24 are not assigned.

Geez, I'm beginning to think that they really didn't want you to do this....


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