[AMRadio] Help Identify This Transformer and Choke

Donald Chester k4kyv at hotmail.com
Sun May 15 13:02:11 EDT 2005

>>The PA-710 is possibly an older version of the CG-710 which is:
>>commercial grade
>>+/-1.5dB 40-10,000 cps
>>audio output, 20 watts,
>>push pull 41, 42, 47, 49, 7B5, 6AK6, 6K6GT
>>primary 14K/20K
>>secondary 500, 200, 16, 8, 5, 3, 1.5 ohms
>>case RC100 (round can with square flange)

That is correct.  In 1948 UTC revised its transformer line.  The PA (public 
address) line was renamed CG (commercial grade), keeping the same numerical 
suffix.  They also changed case styles.  The potted types went from the 
rectangular black case to the familiar round grey can with the square flange 
and terminals on the bottom.  The open frame types were rotated 90 degrees 
so that they became tall and narrow instead of low and wide.  The actual 
laminated core and coil assembly retained the same dimensions, just the 
mounting hardware was changed.

I once rebuilt a defunct open frame PA series power supply choke by 
disassembling the replacement CG counterpart I was able to acquire, and 
remounting it in the original PA style end-bell casting I salvaged from the 
burnt-out choke.  When I reassembled  and repainted it, it looked identical 
to the original and I did not have to drill any new holes in the chassis for 
the mounting screws.


More information about the AMRadio mailing list

This page last updated 17 Jan 2018.