Can you tell me what this thing is?
 

I found it at Orlando HamCation this past Valentine's Day weekend on someone's free table, after they'd packed up and left. I have done as much research as I can with what I have, and I have come to the conclusion that it is the transmitter section of a General Electric mobile radio repeater, perhaps a MASTR series unit? I grabbed it with the hope of cleaning it up and using it for a display/visual interest piece, what with its visible tubes and other parts. I cleaned it and replaced broken and missing tubes. (Ignore the 6SN7GT; it's there to hide an empty non-tube socket, for display.) The large one at right is a 5894 twin tetrode; the rest are fairly garden variety receiving tubes. The unit bears the model or part number 4ET48A11, which Google turns up virtually nothing about. I'm hoping that someone, somewhere, will know all about this thing and can tell me how to apply power to it and light it up. I assume it is a 12 volt DC unit, given the tube heater voltages and the absence of a transformer. There is one lead coming out of the chassis (hidden in pic) with one black, one red, and one uninsulated (ground?) wire, which I assume is the power inlet. Measuring across the black and red wires with my multimeter shows open - perhaps a switch on an external control unit must be closed to power it up.

I don't know anything about this unit. However I think it may be likely that the power supply for the unit is another chassis. One of the non-tube connectors could be the way the power gets to it.
Do you only want to power the tube filaments?
The filament in the large tube could take a lot of power.

It's possible the octal socket is not for a tube but a wiring harness. RCA TVs used octal socket as yoke plugs and convergence chassis harness connectors for decades.

Yes, the power supply is definitely external. I know the socket I currently have the 6SN7 in is not for a tube; I suspect it's for the cable that connects the control head for the unit. As for lighting the tube filaments, it should be doable without much trouble. The large tube (5894A) only takes 6.3 volts at around an amp.

Oh, definitely. My suspicion is that this unit had a remotely located control head, and it connected to that octal socket. I'm thinking another modular part of the whole system connected to it using that 11-pin plug in the clip up top, as well.

That 4ET number tells me its GE. I have some Pre-Progress stuff that has numbers like that. Its FM 2-way equipment, probably low band. I'll look it up in my GE book.

Awesome, thanks! I knew it was a GE something, just not sure what. :scratch2:

Here are the scans.
 

This is as close to it as I can come. Its from the 50's. The octal socket is for a crystal oven.
There are 2 books of schematics covering Pre-Progress but I only have Vol. 1.
Low band (30-50 Mhz) radios were made in three splits. Thats what the suffix numbers indicate.
The reason there is virtually nothing on the web is that these became obsolete long before the internet came about.
I'd hold on to it till the next hamfest and maybe you can sell it for $20 to a ham whose building a 6 meter repeater. The tube type equipment holds up much better compared to solid state when hit by lightning!

Looks as if this model is high band. :scratch2:

http://www.repeater-builder.com/ge/l.../lbi-3283b.pdf

jr

That's even more marketable than 6 meter stuff.
The problem with setting up a repeater these days, is not procuring the equipment.
But finding a cheap site. Gone are the days of locating on a TV tower or tall building for free.
Vertical slum lords have found there's big buck$ in renting their rooftops.
I worked at a station that had 2 square feet of space on top of a hotel in downtown Atlanta. They were charging us $1000 a month (in 2002)! But I think they were providing electric too.

Mid-band GE (36-50mhz) base station xmit section, only 2 multiplier sections. Was good for about 35 watts but not the most stable of beasts, I have several NOS 5894's for that if you want.

Thanks for the info! As this is a display unit, I don't need tubes for it, though the offer is appreciated.