The AM Forum

The conversion pretty much followed along the procedure for the SB220.   The big difference is that the Swan's filament choke has a 3rd winding on the filament transformer's center tap.  I installed the Ameritron filament choke and have tried 10 ferrite beads, turns over the Ameritron choke and a Torrid Core (FT240-31) with 16AWG wire for the 3rd winding.  Having lots of problems tuning the input with my autotuner with power fluctuations as the tuner tries to keep in in tune.  This is with the rig in CW mode.  At one point I had over 400 watts out on 160 but it drops to nothing after a few tries to find the sweet spot.

80- and 40-meters input tuning is not good either especially on 80 meters.

The tank circuit is not original but before the conversion all the bands worked well.  

The 160-meter Tank coil is a T225A-2 torrid core.   I used my VNA to determine how many turns I needed.  Turned out 13 turns works well.

(https://i.imgur.com/BocHP6Y.jpg)

73,
Bill KO4NR

I answered this on eham.

The auto tuner is more than likely hunting.  Because GG means AB2, the tubes are slide ng in and out of conduction.

Ditch the auto tuna, put a 3 band tuned input in it and be done.

--Shane
WP2ASS / ex KD6VXI

Plus, the bias is going to jump around with plate current variations with no bias zener there to settle things. AND, 180pf to ground at the input is probably not helping.

I see this amp project is for sale.

Probably don't need to worry about the threads created now.

--Shane
WP2ASS / ex KD6VXI

Came across a good deal on an Al-80A.
Time to move on.

Thanks to everyone for all the help.  Definitely educational!!
73,
Bill