[Amps] QRO 2500 with really really hot tank toroid

[Jeff Blaine]

A buddy of mine has a QRO 2500DX (runs the pair of x800s).  Has worked 
fine for last 10 years.  And in the last month, the toroid that serves 
the 40/80/160m tank has started to get extreemly hot.  At one point, hot 
enough to melt the plastic mounting hardware.

He rebuilt the coil using larger larger toroids, and the replacement 
coil set is massive.  Functions fine.  But still gets very hot - even on 
CW duty cycle QSOs at 1KW output.  Under PSK or RTTY, well, you can 
grill your dinner if I understand him correctly.

Plate, grid, screen currents all normal.  Power output and even the 
control settings are about the same as before.  None of the other 
components seem to get hot.  QRO says the tank Q is 12 so from a design 
perspective, it's not outragiously high.

It's a symptom with no aparent cause.  At least one that is not jumping 
out anyway...

Hoping someone may have a suggestion on what to look for.

73/jeff/ac0c