Jerry,
Having two 87a's in the inventory and having had them repaired at Alpha and
on-site by Brad, they did inform me that the 87a requires genuine Eimac
3CX800A7 tubes. This is my understanding.
The particular tube characteristics are hard coded into the auto-tune
software. If it doesn't have the correct tubes it may/will not tune
properly. Fortunately, at the time a pair was needed a quick look on eBay
and I found a used pair at a good price otherwise that amp wouldn't have
been repaired or would have waited for a used pair to become available to
complete.
73,
Kimo KH7U
KH6YY Contest Station
Date: Thu, 13 Oct 2016 09:38:45 -0400
From: "Jerry O. Stern" <jsternmd@att.net>
To: "'Jarrad Mitchell'" <vk3bl@outlook.com>, "'Paul Christensen'"
<w9ac@arrl.net>, <amps@contesting.com>
Subject: Re: [Amps] Alpha 87A Alpha Max Upgrade
Message-ID: <006601d22557$1f7ffe30$5e7ffa90$@att.net>
Content-Type: text/plain; charset="us-ascii"
Thanks for the thoughtful reply. I was not aware that the 3CX800A7's had
any unusual failure rate. Almost all I have seen are still making full
output after 20 years though the drive needed may be a bit higher over time.
RF Concepts was selling the Chinese ones at a good price and these too I
heard were not bad. I have two 87A's and I bought lots of spare parts for
the common failures, like the TX pin diodes, etc.
73 Jerry NY2KW
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