After reading NQ5T's adventure in repairing the dial drives
I undersatnd why Frank Lester W2AMJ/W4AMJ called the PRO-310 Hammarlund's
great adventure. The Bandswitch mechanism cost hammarlund about $75.

Frank first task was to call sales manager Frank Sylvester who was at henry
radio getting an order for 100 sets. Frank put the receiver thru some tests
and did not like the performance especially of the IF's so he called
Sylvester back to give him time to figure out what was wrong. He said the
receiver was the gosh darndest thing to get into he had every seen. He
fixed the problem that was in the second IF stage and then completely
revamped the Rf. That the receiver met specs was due to the fast redo by
Frank and the young engineer who had designed the receiver. None of the
Engineers were hams so Frank made them get their tickets so they would see
designs in the way hams see them.

I enterviewed Frank in 1997 and he agrees with a statement made by NQ5T
about "lasting forever" never intended to be 50 years plus! Frank went on
to take over the Super Pro 600 fixes and notes (every goverment contract
wanted some different) and design the basic HC-10 which became the basis for
hammarlund receivers (60 kcs IF's and the Hammarlund patented slot filter)
for the next decade.

Frank became a slient key this Spring at the age of 97.

Lloyd Hammarlund pulled the plug on the PRO-310 after
only 600 units as the margin in the amateur radio market
was too small and no government contracts for the receiver were ever
received try as they might.

Just to find such a receiver in restorable shape is a miracle
Frank told me and this was in May 1997.

happy restoring!

Dave K4JRB