The AM Forum

I purchased a Babcock MT-5A on ebay and I'm trying to locate a schematic.  I found a manual/schematic for a Babcock MT-5B on BAMA but there's more than minor differences between the two transmitters. 

This is a mobile (AM only/no CW) phone transmitter from 1953 that's about half the size of a shoebox (weighs 9 pounds).  It uses a 6146 in the RF final that is plate and screen modulated by a pair of 6AQ5's. 

(http://i228.photobucket.com/albums/ee206/bstout01/_1.jpg) (http://s228.photobucket.com/user/bstout01/media/_1.jpg.html)

       

interesting box.
Probably on the same idea as the Elmac AF67....hopefully constructed better than the Elmac.
google not very helpful......One site has some specs 35-50 W input.
Fred

This transmitter covers 3.5 to 30 mhz continuous and is crystal controlled with a selector switch on the front panel.  It also has built in push-to-talk and T/R switching (rcvr ant and rcvr muting) on the rear panel.  The speech amplifier utilizes balanced audio (no driver transformer) and the modulator is AB1 push pull 6AQ5's.

I'm hoping someone on this forum has the same transmitter with documentation. 

(http://i228.photobucket.com/albums/ee206/bstout01/_57.jpg) (http://s228.photobucket.com/user/bstout01/media/_57.jpg.html)

 

Years ago (B-R-R-R-R) I was with MrMike/W1RC at the old Hosstraders in Rainchester NH. We were strolling around the tables at dusk when we came across a fellow having a fire sale because he wanted to leave. Among the items he had was one of these little Babblecocks in very nice condition. Everything was $10, and Mike ended up with the Babblecock while I got an old Gonset CB with the original cool Astatic crystal mic.

I don't recall there being a manual or any other printed material with it and I think it's long since gone to a new home, but Mike may have picked up documentation somewhere along the way. He pops on here from time to time.

BTW, I thought it used a 2E26 instead of a 6146. Very stout little rig though, to be sure. A good find.

Nice find!! Another set that is similar is the Gonset Commander. It's a 6146/6AQ5's or 7C5's. Iron is out of the WWII surplus SCR-522 VHF rig.
Hope it's an easy fix for you to get it on the airwaves!!
Terry N3GTE
ps.If you get too frustrated with it just sent it my way!

Old Buzzard Les lives on!

Well, It's making RF on 3.880 now.  About 18 (Bird) watts which is all it's suppose to put out.  It takes two voltages (6.3 and 350) to operate.  I took one of my Heathkit HP-23B power supplies and wired it for 240 primary.  When I plug it in to 120 I get just under 400 from the 800 volt supply and the 12 volt supply becomes 6 volts.  It was the easiest power supply mod I've ever done.  I'm now having fun getting the speech amp/modulator to work.

Too much fun!   Wish I had a schematic!!!

I've got the audio playing after replacing two .005 coupling caps and locating a missing ground.  It takes about -18.7 dBu (90 millivolts) into the speech amp to fully modulate the final.

Too much fun!