The AM Forum

Looking for the subject schematic/manual documentation to support restoration of this RCA broadcast studio monitor amplifier which was used as a speech amplifier Type 7179A to drive a pair of 805s that modulated a pair of 813s in the 1940s RCA ET-4336 export shortwave transmitter.  Both the 82-C and ET-4336 are included in RCA’s broadcast equipment catalogs from the 40s, and possibly 1950s.  For many years, I have had the complete MI-7179/83-C amplifier, and the ET-4336 modulator deck, plate, mod, and filament transformers, various filter chokes, large power resistors, and a full set of new 813s, and 805s.  I expect to start putting a transmitter together this fall with all this stuff, using an RF deck built abound a pair of grid driven 813s I acquired a while back.

Put the 82-C on the bench today.  I had used it many  years ago as the duty receive side audio amplifier in the shack, but it has been a shelf queen apparently too long, as it’s once very clean and smooth audio is now quite crunchy and distorted at anything above very low output levels.  Tubes (four 1620s/6J7s driving PP 1622s/6L6s all test good, but there are a number of paper and electrolytic cathode bypass caps that are all original that likely have gone bad, so a schematic and/or tech manual would be helpful at this point.

Googling has come up with links to the RCA broadcast equipment catalogs, but no luck so far on schematic it
manual, any leads on same appreciated.

I have the RCA Type 82-C1 complete manual. 4 1620's driving 2 1622's, 5U4 rectifier.
Full title is Monitoring and Recording Amplifier ( MI-11209-B1)

Thanks Pete, will email you re getting a copy of that documentation specifically for the 82-C.  I eventually came across archived documentation that covered both the ET-4336 transmitter and the MI-7179A speech amp online.  There are some slight differences between that manual and my amp, but close enough.  Just finished changing out all the paper caps for Orange Drops, and checking for out of tolerance resistors (none found).  Went up from .1 uf to some .25 ufs that I had on hand for the interstage coupling caps.  Although none of the caps I pulled showed any leakage with a low voltage ohmmeter check, the amp is now singing for its supper driving a pair seriesd-up Boston Acoustic CR9 floor speakers.  It CRANKS! Very clean and smooth low end.  Can't believe this amp is only putting out 12 watts into those BAs.