[Amps] Amp Conversion Update

Paul Christensen w9ac at arrl.net
Fri Aug 29 18:33:28 EDT 2014


I'm making slow progress on my amp conversion.  Some of you may recall that 
an Alpha 77Dx "beater" is being converted into a custom amp.  At this time, 
the microcontroller code is nearly finished, the new front panel is complete 
with a quad set of 250-degree analog meters, a new front panel switch-bank 
PCB was designed, and much of the hardware mods have been made.  I'll have a 
few pics in about a week.

The loading cap pair are jettisoned and I'm using one 7-1000 pF vacuum cap. 
But here's a problem I'm up against.  To add the vacuum cap, I need the same 
turns-counter hardware that Alpha used.  Images in the links below.  Alpha 
used a pair of keyed disks on the 1/4" shaft ends to engage a Nylon spacer. 
The opposite side of that spacer then engages the vacuum cap.   The hardware 
is press-fit such that the panel can be removed without the need for shaft 
couplers.  Due to space considerations, there's just no way to access 
coupler set screws between the front panel and inner panel.  That's why 
Alpha chose this method.

http://72.52.250.47/images/1P.JPG
http://72.52.250.47/images/2P.JPG
http://72.52.250.47/images/3P.JPG
http://72.52.250.47/images/4P.JPG

Apart from making my own, does anyone know where I can find this hardware? 
If there are no leads, I’ll check with RF Concepts and Dick Byrd, N4UQ after 
the holiday weekend.  Tnx!

Paul, W9AC



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