[Ron Ramirez]

It might be that the model 70 does not have enough overall gain to support an avc operation, being only a seven tube set and especially with no multi-function tubes. I suppose I could replace the 24 detector tube with a 55 tube and install a conventional diode detector and triode amplifier as was used in later designs with the 6Q7 or 6SQ7. But then I would have to change out the tube socket also. That is not an option which is easily reversible.

I disagree, the Model 90 with AVC and a single 47 output tube has the same front end as the early 70, just modified to use AVC.

In my mod, I switched the RF and IF tubes (originally type 24) to type 35/51 as these, being remote-cutoff tetrodes, are designed for AVC use. I believe Ed used 35/51 tubes in his mod.

I'll try to post a schematic later.