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Re: [Amps] Looking for Alpha 87A expertise (David W6DR)

Subject: Re: [Amps] Looking for Alpha 87A expertise (David W6DR)
From: bmm57 <>
Date: Tue, 16 Mar 2021 07:35:25 -0500
List-post: <>
UM4006D are now $60.00 each at Mouser Elec.Sent via the Samsung Galaxy S9+, an 
AT&T 5G Evolution capable smartphone
-------- Original message --------From: Date: 3/16/21  7:20 
AM  (GMT-06:00)mTo: Subject: Re: [Amps] Looking for Alpha 
87A expertise (David W6DR) I wouldn't say I am an expert on the Alpha 87A 
although I did own one anddeal with issues inside it for several years.  It was 
a good amp and itsbest feature was the quiet and reliable PIN diodes making 
real QSK not onlypossible, but normal.  I never managed to kill mine.  I did 
trade it in toAlpha for a 9500.  As far as PIN diodes are concerned, you can 
download theSPEC sheet from Micro-Semi (UM4006D/SM) and for 1N4007s you can 
download theSpec sheet from any company that makes them.  UM4006D/SM PIN diodes 
runabout $16 per; 1N4007 diodes run about $0.03 per.  So on price it ought tobe 
fairly obvious that there is a difference here.  Looking at the specsheet, the 
speed of switching of the UM4006D is incredibly high (like 5uSec) - the 1N4007 
doesn't appear to be specified except to confirm that itworks well at 60 Hz.  
If 60Hz works for you - go for it.  But this is a T/Rrelay we are talking about 
and you don't want the power going to the wrongplace for very long.  And 1/60 
second is VERY long for 1500 Watts to begoing to the wrong place. (1/60 second 
= 16700 uSec).From what I have read, the failures tended to occur in earlier 
units due toa less than optimal installation protocol during manufacturing. 
(10/05/2017Amps Post from WC1M).Microchip Technology Inc. appears to have units 
available for sale right now- possibly others, and there appear to be 
alternates available.I am enough of an expert to know that I would rather 
replace a dead partwith a same thing replacement than attempt to reengineer a 
critical circuitthat will kill my expensive transceiver in a few microseconds 
if I get itwrong.  Especially if the part costs less than $20.  Good luck.Dave 
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