[Amps] More on Toroidal Tank Circuit Issues

[Jim W7RY]

I may have to eat some crow here about using dedicated toroids on 160 and 80 meters...

I built an 8877 amplifier based on the K8RA (SK) 3CX1500D7 amplifier. http://www.k8ra.com/index_049.htm

Mine is shown here: http://s900.photobucket.com/user/w7ry/media/8877%20Amplifier/DSC_0037.jpg.html?sort=3&o=47 

And here: http://s900.photobucket.com/user/w7ry/media/8877%20Amplifier/P1010225.jpg.html?sort=3&o=13

The lower toroid is 160 only and the upper one is 80 meters only (with 10,15,20 and 40 coils added in of course).

I’m using a shorting band switch 6 position. 


On 10 meters, the 160 meter toroid (lower one) gets so hot, the fiberglass tape has turned brown, and the Teflon wire is melting the Plexiglas that the toroid's are mounted on.

I know all about trying to use a tapped toroid for multiple bands is wrong (except on the L coil of the Pi-L circuit, and see my postings about the Commander HF-2500 and K1TTT’s pictures of same) but WHY is the 160 meter toroid getting so hot when using 10 meters?  It's mounted very close to the loading vacuum capacitor is the only thing that I can think of. But the weird part, is that this just started. During all of the testing, there was no problem, but now, its really getting HOT!

When testing, I had the top cover off of the amplifier, now that I’m using it, the top cover is on. I’m going to try the test again with the top off and see what happens.

On 80 and 160 meters, the toroids are normal temperature (around 100 degrees) and everything works just fine since I’m not shorting turns on the toroids.

Ideas?
Thanks and 73
Jim W7RY