[Amps] Alpha 77dx

Harold Mandel hmandel at barantelecom.com
Fri Jun 6 13:40:12 EDT 2008


The two-tube '77 sometimes says "77Dx" on
the beige front panel, but is a "77Sx" machine.

There were several editions of '77's:

Very, very few 2-tube '77's were made by the
ETO factory. These are rarer than hens teeth.

The majority were home-conversions. You need to
look carefully at the craftsmanship in the RF plenum
to see how the second tube kit was added. There
should be a toroid coil with two different colored
wires, (red, green) to split the signal between the

Next, there were several different power transformers.

Not all were PWD, and not all were made for adding the second set of
filaments. You can tell by looking at
the Molex connector on the power transformer. The
xfmr made for conversion to 'Sx has two sets of
pins for the separate tubes.

If the machine is in mint shape, spend six or seven thousand. There are
no more being made, and they
are truly beautiful.

Dave Wilson can get you a set of black powder-coated
panels specifically for 'Sx versions, and they are
not only beautiful, but since he was in on the design
they can be seen as authentic. 

Contact me off the list if you need any further clues.


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