[Amps] Alpha 87A Alpha Max Upgrade

[Paul Christensen]

>"Your biggest problem with the 87A will be tubes and TX pins." 

 

For folks curious about the PIN issue, the original Alpha 87A Tx PIN is a
MACOM MA4P4006D with a Vr rating of 600V.  The "D" suffix signifies an
isolated stud mount - and that's the trick in finding a direct or alternate
replacement.  It's not that high-power PIN diodes are going obsolete anytime
soon.  

 

The MACOM MA4PK2003 is in current production, and is a heftier replacement
with its 2KV Vr rating.  This diode uses a #6-32 mounting stud instead of
#4-40 as used on the 4006D.   So, replacement of the 4006D with the 2003 may
be a viable option for folks who don't mind drilling the rear chassis
mounting hole a tiny bit larger - and get a more robust diode in the
process.   Considering where we are in the 87A's almost 30 year life-cycle,
I doubt a change to the 2003 diode would affect resale value much one way or
the other.  Current pricing though Mouser is $66 ea. in small quantities.
Carrier lifetime is fine down to 1 MHz.  One diode is roughly the price of a
Jennings RJ-1A vacuum relay.  The 87A uses a PIN pair for Tx.  

 

Also look for these on the auction site.  I've purchased several over the
years for much less from industrial component sellers.  

 

Paul, W9AC 

 

From: BRADLEY FOCKEN [mailto:BFOCKEN at msn.com] 
Sent: Thursday, October 13, 2016 3:38 PM
To: Jerry O. Stern <jsternmd at att.net>; 'Paul Christensen' <w9ac at arrl.net>;
amps at contesting.com
Subject: Re: [Amps] Alpha 87A Alpha Max Upgrade

 

Hello Jerry,

 The pals can be cloned and can be found. Your biggest problem with the 87A
will be tubes and TX pins. The pals rarely ever fail and can be obtained
from Alpha.

 

Brad Focken

 <mailto:bfocken at msn.com> bfocken at msn.com