CAS voltage not the same

[Paul Birkeland]

The next step would be to play your 100Hz tone into the amp through both channels.  Measure the AC voltage between 5 and 10 on each transformer, then also measure the AC voltage at the speaker binding posts.

[bqc]

question on measuring at the speaker terminal, do I need to have speaker or dummy load or should it be left open?

[Paul Birkeland]

I would leave it open.

[bqc]

So with the source at full volume, the AC voltage across 5 and 10 of left transformer is 52V  and right transformer is 122 V
AC voltage across speaker terminal left 2 V, right 8 V
BTW I also measure the inductance of the 16 ohm secondary (which is what I am using)  Left transformer 0.2 mH  ,  right trans  37mH

[Paul Joppa]

The photos show a wire connected to transformer terminal 6, and none connected to transformer terminal 8. This is not consistent with the 16 ohm wiring. I can't see the rest of the secondary wiring well enough to say more, but the voltage and inductance data suggest a short across a portion of the secondary.

[bqc]

Sorry, the pictures were old and were taken when I had it wired for 8 ohm, I will retake pictures

[bqc]

The photos show a wire connected to transformer terminal 6, and none connected to transformer terminal 8. This is not consistent with the 16 ohm wiring. I can't see the rest of the secondary wiring well enough to say more, but the voltage and inductance data suggest a short across a portion of the secondary.

[Paul Birkeland]

One of your short red output transformer jumpers looks to be touching the chassis.

[bqc]

Do you mean the jumper between 1 and 2 of the transformer ? I lifted the amp and look  at it from the side and see that there is a 1/2 gap between the jumpers and the chasis so they are not touching.

[bqc]

So what to check next  to find out why there is a short in the secondary

[Paul Birkeland]

Take all of the jumpers and leads off the transformer you believe is bad, but leave the wires on 5 and 10, then recheck the AC voltage across 5 and 10.

[bqc]

with all leads and jumpers removed except at 5 and 10 on the left transformer, with input at full volume, the AC voltage across 5 and 10 on the left transformer is 55V while the AC voltage across 5 and 10 on the right transformer is 120 V

[bqc]

So can we conclude that there is a short inside the transformer on the secondary winding? If so what are my options? Is the transformer still under warranty ? if not how much would it cost to get a stock replacement transformer and how can I order it?

[Paul Birkeland]

Now lift the wire off terminal 10 on the output transformer, then measure the AC voltage between this wire and terminal 5 on the output transformer.

[bqc]

with wire on left transformer terminal 10 lifted, AC between wire and terminal 5 on left transformer is 140V, a jump from 55V to 140V, while the AC voltage between 5 and 10 on the right transformer remains at 120V