Patrick the company did use two sizes of transformers in the 77 series. You
are more likely to encounter the smaller transformer in a really old rig.
Here's a quick fool-proof way to tell: Pull the plug out of the wall,
first!! then disconnect the transformer's AMP connector which has the most
wires. Look at the transformer connector and see how many pins are missing
from the array. ONE hole should not have a pin. If more than one hole is
showing, it's the small transformer and does not have the filament winding
for the second tube.
You are right, most SX's are DX's that have been converted in the field.
The ones lacking in quality and/or completeness were probably mine. I'm
responsible for about 30 of them. Actually most two-holers I've seen done
by others looked pretty good. Kits have always been available but the
instructions left some doubt as to proceedures.
As for the state-of-the-art ness of the older Alpha rigs I would say they
stack up as well as most manual-tune amplifiers sold today. If you really
want modern, buy a 87A!
The 8877 tube used in the 77 is widely used by the medical industry and for
that reason they are always available on the used market....and I'm always
looking for sources.
73, Dick
At 12:49 PM 3/11/97 -0500, you wrote:
>Hello Dick,
>
>Read your reply on using the 77SX on 17 & 12. I emailed him about the same
>basic info but with the warning that I was basing it on reviewing diagrams
>and experiences with other amps - not actually using a 77SX.
>
>>From your reply one would assume you are very experienced with the 77. I've
>considered building a two hole 8877 or finding a 77SX, but have been told
>some possible tales that raised an eyebrow. I wonder if you might clear a
>couple points for me.
>
>Regarding 77SX:
>Was different transformers used, and if so, which one is best for the pair
>of 8877's?
>
>I've heard that most SX's are DX's that individuals converted, and the
>conversions often were lacking in quality and/or completeness. Any thoughts
>along those lines?
>
>Considering the age of the design, are these amps still reasonably
>'state-of-art' compared to the various QRO offerings using newer designs and
>tubes?
>
>I realize subjective side of some of this, but, bearing in mind your
>history, I would think anyone not interested in modifying a specific unit
>would offer excellent subjective points based upon experience (and lived to
>tell about it!).
>
>Thanks for any input Dick, and glad to see the reflector working so well.
>
>Bests,
>
>Patrick
>WB9IQI
>
>
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