[Amps] Alpha Switching Diodes

[Jim Thomson]

Date: Wed, 1 Mar 2017 00:53:46 -0800
From: Jim Brown <jim at audiosystemsgroup.com>
To: Amps Amps <amps at contesting.com>
Subject: [Amps] Alpha Switching Diodes

I've heard that Alpha came up with a fix for problems with their 
switching diodes on the 87A and 89 amps. I just bought one of each. Can 
anyone shed light on this?

73, Jim K9YC

##  yeah,  its called  vac relays, used on  newer alpha amps.  Having said that,
the pin diode tr switching diodes in the 87-A never seem to have issues, where
as the same pin diodes in the manual tune 89 do..dunno why that is. 

##    Gigavac GH-1,  Jennings RJ1A, or a kilovac HC-1 are all the same, and all 
will easily switch in less than 1.8 msecs. The gigavac GH-1 is the best of the bunch,
and will easily hi pot test to over 7.5 kv.

##  a buddy used 3 x gigavac GH1s  on his  hb 6m  GS35B amp.   1 for input, 1 for output,
3rd one for the bias.   Then its easy to sequence them for  qsk  operation.  With a vac relay
on both the input and the output, then you can also stuff  2 kw through it on bypass. That
comes in handy when you wire 2 or more amps in series, nose to tail.  I do that with my 4 x drake
L4B amps.  Then the key line from xcvr to a simple rotary switch.  Output of rotary switch is
fed to each of the 4 x amps key line inputs.  Simple mech interlock. Then only 1 amp can be 
keyed at any one time. 

##  a buddy has an alpha 87-A.  It has the high and low  B+  position.  On the low B+  position,
running half power, the plate xfmr buzzs.  Never did figure that one out, has anybody else
experienced this ?    The new alpha amps dont have a hi + low  B+ position, too bad.  That
comes in handy some times.  If you want lower power, its more eff when using lower B+.

Jim  VE7RF