[rescue] Serial console - break "filtering" connection - resistor method

[vom513]

Hello all,

So I have a couple of dumb terminals (the one I’m using to test now is a WYSE-160).  I’m using an IPX as the test machine.  So this has the DIN-8 to DB25 cable.

As we all know, by default, when dropping the console connection (i.e. turning the terminal off) - Suns will drop to PROM/debugger :(

Years ago there was supposedly a pricey cable/dongle (NuData 4273) that would “shield” the Sun from break signals.  Another hardware solution I’ve seen mention of is putting a resistor in the connection to disable break signals.  This is the rabbit hole I’m going down.

I’m trying to use this:

https://hea-www.cfa.harvard.edu/~fine/Tech/cs1.2/Sun-serial

According to that, we are pulling -5v off pin 25, running it through a 4.7k resistor, and connecting this to pin 3 on the Sun side ?  Am I reading that correctly ?

On my IPX - I seem to get nothing off pin 25 (testing with DMM, and tried the shield as well as pin 7 as ground).

I do however seem to get -5v off pin 1.  If I’m reading that Harvard URL right - I should be able to use pin 1 in place of 25 ?  I’m leery of this as I’d really rather not blow up the serial port and/or machine itself…

So any info anyone can give me on this would be greatly appreciated.  I’d really like to be able to power my dumb terminal off/on as well as use a serial switchbox without dropping the box(es) to PROM.

Thanks.