another VibroChamp problem

[mresistor]

This is a 66 Vibro Champ I have on the bench. It's had a full e-lytic recap, including the PS filters. New JJ 12AX7's and New EH 6V6, old RCA 5Y3GT. The amp sounds great and the trem works very well. Problem is when the volume is turned down to 2 and below it sounds like the 6V6 is emitting a very high pitch sound, not a hiss, but more like and rf sound. Makes a popping sound when it starts to happen. Like a very high freq oscillation. Fades out mostly in time, but when volume is adjusted again and turned down, it's back. When I turn up the intensity pot to 3 or above the problem goes away, whether the trem is on or off. Does this with any 6V6. Also tried different 12AX7's. No difference.
Here are some voltages at idle. Htr volts are a tad high but nothing unusual. Has correct replacement OT from AES. High voltage is pretty high, and the PT has an orange lead - bias lead?

V1 pin 1 - 228
         2 - 0
         3 - 1.67
         6 - 238.4
         7 - 0
         8 - 1.87

V2     1 - 177.5
        2 - .002
        3 - 1.97
        6 - 389
        7 - 177.2
        8 - 182.1

6V6   3 - 390
        4 - 389.8
        5 - 0.16
        8 - 24.71

I've replaced the volume pot with no change. The amp has a 3 prong cord, no death cap.
Chop-sticked like a hungry Chinaman to no avail.  

[Tiny_Daddy]

Try disconnecting the feedback. Since it's a new OT there's a chance the primary is connected backwards.

[mresistor]

disconnected feedback - all is well - touch feedback to terminal and the problem returns - should I reverse the primary wires of the OT?
and why the primary wires versus the secondary wires?

[Leevi]

It's probably a some kind of oscillation.
Add a 1.5K resistor on the power tube grid (as close as possible to the pin 5).
Try to move the wires with a chopstick when the problem is on.
/Leevi

[mresistor]

Thanks Leevi - Tinydaddy nailed it.  I was reversed OT primary leads..   Sounds great now and works properly.
Thank you TD for the help.