Heat heat and more heat??

So, after taking the reading as you suggested Al, i read 0.4 ohms on the right channel xlr input and a fluctuating reading on the left channel xlr input. When I took the measurement between the AC safety ground and the xlr, the right channel was also 0.4 ohms and the left fluctuated all over. I switched the xlr/rca switch on the amp and the results seemed to be the same.
Thanks again.

Strange that the two channels gave different results. Not sure how to explain that.

Just to confirm that the correct pins were measured, pin 1 of each of the female XLR connectors would be the pin closest to the right side of the connector, when viewing the connector from the rear of the amp.

Given those results, additional measurements that might be useful to know would be the resistance between the ground sleeves of the two RCA connectors, and the resistance between pin 1 of the two XLR connectors.

In any event, I would still expect connecting the black wire to XLR pin 1 to work, although using the right channel XLR connector seems like the surer bet.

Best regards,
-- Al

Al, the reading at the two RCA's is 0.4 ohms, same as at the two xlr's.
I took the caution of replacing the battery in the meter today ( even though apparently the old one was ok), which seemed to slightly solidify the readings, so I re-took the reading at the left xlr and rca ground, it fluctuated a little but I suspect the true reading is also 0.4 ohms. Seemed to float around there.

Sounds good! So pin 1 on either XLR connector should be a good point for connection of the black wire from the sub.

Best regards,
-- Al

Thanks again Al. As soon as the amp comes back from the factory, I will connect the sub as suggested. Appreciate all the help.