[AMRadio] Hot coils

[CL in NC]

I am restoring a Halli HT40 that I have had sitting around for a while, using the ER Mag article from Phil Legate as a guide.  During the work, found that the  80 meter driver coil was modified for some reason.  The 40 meter driver measured 15uh, the 80 meter had been unwound down to 15.5, not sure what the unwinder was after.  So, I made a coil on a slug tuned form and got the required 60uh and it worked like a champ.  With the rig running on the bench feeding a dummy load, AM was fine until I saw smoke.  That 80 meter coil was so hot, it was melting the coil dope I put on it.  My junk box had nothing close to 60uh and big,  so I took the old original Halli cut coil and spliced 45 turns on it to get 60uh.  Tried it, tuned up fine, again, after keydown of about a minute, it was as hot as a 2 dollar pistol.

I switched to 40 meters where the unmolested  driver coil looks identical to the 80 but half as many turns, and 15uh, and did the same thing.  It did not get as hot as quick, but was noticeably warm also.  I wound a toroid coil too, but the Q was too low.

So, how many rigs out there have hot driver coils on 80 and 40?

Another thing about the HT40.  Phil recommends removing the RF level circuit and convert it to read tube cathode current.  I have to agree as I found that the RF Level circuit, when the meter is in RF Level, changes the Z of the output and loads the circuit where I was losing 10-15 watts of CW power, and almost all the AM power.  Leave the meter in grid position, and I get 50 watts CW and almost 20 of AM.

Charlie, W4MEC in NC