• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Output tranny

I have two Edcor GXSE10-8-8K single ended tranny on a decaware amp. One channel is very quiet and the other is fine. When I reverse the output trannies the quite side follows the output tranny. Can I conclude a bad tranny
 
Occasionally, some transformer wire numbers or wire colors are switched during manufacture (swapped leads).

Turn the amplifier off, unplug it, and then wait until the bleeder resistors discharge the B+ capacitors. Check B+ Volts with your DMM.
(You Do have bleeder resistor(s), Right? Prevent the "Surviving Spouse Syndrome"

Now that the B+ is fully discharged, take your DMM and measure the primary DCR, and measure the secondary DCR of the Two output transformers.
Are they equal?
How much different are they?

Note: some DMM ohmmeters in auto-range mode will "hunt" and keep changing ranges when measuring the DCR of inductors, such as an output transformer.
So . . . use a shorting jumper across the secondary when measuring the primary DCR;
and use a shorting jumper across the primary when measuring the secondary DCR.
 
Thank you for the answer I did as you suggested, the measurements were basically the same primary 206 ohms, secondary 0.7 ohms. I do not believe it is the amplifier because the good output tranny plays well on either channel