Power transformer hum

[luthierwnc]

Hi all,  Back after hurricane clean-up.  A few years back I made my own version of a Matchless HC-30.  Great sounding amp but it always had a little hum.  That wasn't much of a problem for jamming but I've recently tried to record it and decided that hum has to go.

With all the tubes out, no speaker, on standby it's the same 60 Hz hum.  Volume controls have no effect.  It's on the bench now and an ear test confirmed that's the issue.  I paid for the same kind Matchless uses right when Pacific Transformer took over (or re-took over) building them.  Got all three direct.  Right now I'm thinking my next move is to disconnect every output wire and listen one more time but with no tubes (rectifier, power or preamp) there shouldn't be any surprises.  I am using the 6.3v ground rather than 100R resistors but I'm not married to it.  I could also take the ground off the power tube cathode ground.  It has a lug on one of the PT bolts now.
Any other ideas before I start de-soldering?  I'm leery of getting an identical replacement and getting the same result.  And it's an unusual bolt pattern.  The layout (attached) is nothing like a Matchless but everything else is dead quiet.Thanks, Skip

[shooter]

is the green wire running with the red wires ground??  red B+??  that's a recipe for hum induced coupling. 
ground should "cross" B+ at 90 degrees not run parallel.

[luthierwnc]

I separated them.  No change.  sh

[pdf64]

Any hum with no valves is completely unrelated to the amp circuit.
It's all about magnetic coupling.   

The mains transformer core is aligned such that it is sending lines of flux along the chassis. Hence the coupling between it and everything else. Sorry, but to fix this, I suggest the first step is to turn it 90°.

[luthierwnc]

Thanks gents,  Looks like I pull the PT.  I'll see if it hums out of the chassis before I try to shoehorn it in sideways.  That first cap canister will need to be moved and probably the choke too if that's the case.  Big sucker.  More when I get it.  Cheers, sh

[luthierwnc]

I pulled the tranny, hooked it up to the Variac and it hums all by itself.  Worst case scenario but now I know.  Next question is; do I see what Pacific has to say or maybe look for an AC30 PT with similar voltages?  It's never easy, is it?  Thanks, sh

[luthierwnc]

Turned off the dehumidifier, heater motor and everything else making noise in the basement.  The transformer isn't as loud as it sounded when in place.  I'm going to reinstall it with some variations on the lead dress.  If I get the same issues I'll consider more drastic solutions.  sh

[luthierwnc]

Last one, I think.  I tightened the four bolts holding the laminates, now it's quiet.  sh