Does anyone have a schematic for this unit or a working example? There's three tubes. One looks like a 6CB6 but has only a 6-digit number stamped on its shoulder "6B1000", a 6C4 and a JAN-CNU 7193, octal triode with two top caps - one plate, one grid tied together and funtioning as the rectifier.

See link for photo http://www.ebay.com/itm/Superior-Instruments-Vacuum-Tube-Signal-Generator-660-A-AS-IS-cut-cord-/300807987985

It works OK but does not modulate a tone onto the output. I see two transistors in the audio output circuit, one of which broke off its leads. The transistors are Raytheon CK721, an early PNP-germanium type. I can replace them with ECG-102s and see what happens, but they were added later by the looks..:scratch2:

Bama has one for a 670-A. Don't know if it would be similar or not.

Not similar, the 670 A is a different machine altogether, and more like a TV analyst in that it also has FM and generates Horiz and Vert sweep signals.

The 660-A is very basic, just an AM unit ranging from 100khz to 13 mhz. I have a Hickock 277X that has many more features

That was equipment that was sold on the back cover of Popular Electronics. To me, It was comical to see what they used to make some of this equipment. I have a TV pattern generator, that is simular to a color generator, only produces horizontal or vertical lines. It used that high frequency triode and two acorn tubes.
I have a Genometer that has that 6B1000 and someother dual triode type and that rectifier 7193. Some of the other parts are Philco surplus.
I bought it for the knobs and the power transformer.

A little persistence turned this up;

This one is ORIGINAL and has two 6BE6 and a 6H6 as the rectifier....interesting.

http://www.youtube.com/watch?v=mqIoHR7pq6U

My unit was heavily modified with an on-board, fixed frequency modulator powered by a battery. Not only that, the attenuator switch was replaced with a pot to adjust the modulation level.

It seems like finding a schematic to return it to original may be a long shot. I just plan to do the alignment as per the video using a frequency counter.