Federal TV Corporation Audio Compressor AM-864/U

A similar unit sold on eBay recently for $780.00
It looks almost identical and I think it's the same thing. The unit on eBay (view images) was not identified as to model#, and had what looked like an additional pot added to the front panel (Thou shameful driller of holes, methinks!) so we have only the images to go by.

Anyway, this compressor has a very warm and pleasant tube sound, and is certainly one of the very best ever made. The circuit is balanced all the way throughout the unit, using high quality transformers and push pull circuitry. The compression is achieved by reducing the G2 voltage on the input stage during peaks. Input and output impedances are 600 ohms (balanced and floating).

Most of the caps which have any DC across them have been replaced. Large filter caps have been added across the original B+ filters, which were not bad or shorted, but it was done to reduce fluctuations in B+ due to line variations.

There is a very nice schematic on the inside of the bottom plate. We drew this copy.

The unit is 'tropicalized', meaning it has a coating on the internal electronics, which prevents corrosion and rot.

The rectifier tube has been removed in this specimen, and two diodes and a resistor have been substituted, under the chassis.





Adjustments for technician! Not for gefingerpoken!

AC plug, a two-blade recessed type. It has a hole in it where the line wiring would come through and connect to the screws. A regular cord has been run through this hole for power.

The picture does not do the meter justice. It's a lovely bakelite black cased meter front, with a lighty yellowed face, and all the nomenclature is in excellent shape and very easily readable.

Underside. Notice the gold tone of the image. This is mostly the tropicalizing coating, which has protected the innards for all these years.

We replaced some of the caps. Note the tropicalizing coating on the original parts.

Chassis top. A bit dusty, but very nice.