Do they use the same pin diodes in the alpha 86 amplifier?
Fern VE7GZ
-----Original Message-----
From: Paul Christensen
Sent: Thursday, October 05, 2017 5:49 AM
To: amps@contesting.com
Subject: Re: [Amps] Alpha
At some point in the future, 87A prices may reach a point where it's
worthwhile to own a donor unit, especially as 3CX800A7 tubes become more
expensive to purchase. I see the most problematic replacement parts being
the ROM/RAM chip sets, and Tx PIN diodes.
For those like me who will own their 87A amps until kaput, consider
purchasing an extra set of TX PIN diodes before they're gone as that part is
now obsolete by Microsemi. The original MA/COM MA4P4006D PIN diode was
subsequently renamed as the UM4006D when Microsemi took over the product
line. The "D" suffix signifies an isolated #4 stud mount. Although other
high-power PINs can be used, it's nice to take advantage of the 87A's
"thru-panel" heat sink.
Richardson RF has the PIN diodes on close-out. This spring they had a
supply of 275+ diodes. Today, stock level is 50 units and I doubt more will
be manufactured in the isolated stud-mount version. Price is only USD
$24.75 in small quantities. That's much less than original pricing. Two
UM4006D diodes are used in the 87A/89.
http://www.richardsonrfpd.com/Pages/Product-Details.aspx?productId=855450
Paul, W9AC
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Dick Green WC1M
Sent: Thursday, October 5, 2017 12:29 AM
To: gm5bkc@gmail.com; amps@contesting.com
Subject: Re: [Amps] Alpha
I figured out the life of a vacuum relay (RJ1, HC1, GH1, all rated for 2
million cycles) in QSK contesting in CQing and also S&P. When running
(holding a freq and calling CQ) you get about 20,000 QSOs for the
rated 2 million cycles, in S&P it's about 33,000 Qs, using my call as an
example, with the CQWW contest exchange.
Glenn AE0Q
At first blush that number looks very low to me. After all, there are quite
a few very active contest stations here in New England that do 10,000-20,000
QSOs per year and you don't hear lots of stories about vacuum relays needing
to be changed frequently.
But I think that's because the vast majority of highly active CW contesters
don't use QSK for running. Too much noise, which gets really fatiguing when
you do 3,000-4,000 QSOs in a weekend. Besides, many contesters grew up with
amps that couldn't do QSK (meaning frame relays), so they've always used
semi break-in. Some use QSK for S&P, but even then it's not all that
necessary (if you're spending so much time in pileups that you need QSK,
you're losing.)
The number of relay closures for semi break-in is dramatically lower -- off
the top of my head I think it must be 1/100th as many as QSK closures, maybe
less.
Of course, relay closures have never been an issue for me because for the
past 22 years I've done virtually all of my contest running on an Alpha 87A.
And in semi break-in at that. :-) I did have to change out the PIN diodes
once, but that had little to do with cycles -- just a L1 arcing on the T/R
board. I had to change out the relay on my Acom 2000A shortly after I got it
because the factory had a bad run of HC1 vacuum relays. It's been going
about 17 years now, though mostly for S&P duty.
I've been lucky -- I've been able to do numerous repairs to my 87A without
having to send it to the factory. But I do worry about parts availability.
That problem started a long time ago, and it will eventually force me to
replace the 87A. On paper the 9500 would be a worthy successor, but honestly
I would want to make absolutely sure the amp doesn't still suffer from the
problems it had early on. And it may be tough to justify investing in a tube
amp with legal limit solid state amps getting better.
73, Dick WC1M
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