[TenTec] Corsair II U10 Problems

[Jerry Haigwood]

Stuart,
    I have been gathering parts that are used by the Corsair.  It uses
several 2N3866 as amplifiers in the receiver.  It also uses a lot of MPS3693
and MPS6514 transistors.  I have purchased a bunch of 2N4124s which will
cover most of the MPS series.  I also purchased a lot of small electrolytic
caps used in the Corsair (1uF/50V, 4.7uF/50V, 10uF/50V, etc.).  I am still
gathering parts but I hope to find a spare for just about everything since I
really like the Corsair.  I will keep my eye out for some MRF458s and some
MRF415s.  I really like the PTO since I don't get any phase noise from a
PLL.  I have a Huff and Puff on order but I will need to test it thoroughly
to determine if it adds any noise.  It is from Cumbria Designs in the UK.
Their URL is <http://www.cumbriadesigns.co.uk/x-lock.htm> It looks like a
nice easy to install unit.  I'll let you know how it goes.
Jerry W5JH


-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of Stuart Rohre
Sent: Thursday, June 02, 2011 3:15 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Corsair II U10 Problems

Jerry,
There are a couple of legacy transistor manufacturers.  One mostly for 
ICs is Lansdale Semiconductors.  Then there is the universal 
replacements of NTE.  There is in fact another industrial manufacturer 
of obsolete transistors.  It is Advanced Semiconductor Inc, and they 
feature MRF parts.  I think they were the folks who bought the drawings 
and processes of Motorola RF division.

Note that MRF was a Motorola part, but Moto became Freescale 
Semiconductor.  I think the discrete products spun off as ON 
Semiconductors.  I see they are not listing RF but do list some types of 
transistors such as drives.

There is a lot of surplus semiconductors languishing in warehouses, and 
sometimes in old local surplus electronic parts houses of the few that 
are left.  You might make an effort to get spares which would enhance 
the resale of your Corsair just to have a spare set of finals.  If ever 
you sold it.  If you look in the boxes under hams' tables at swap meets 
a lot of times you find discrete transistors and many hams don't realize 
what they have in these old boxes.

You are right, many substitutions can be made for old transistors.  Non 
conventional solutions might even include paralleling multiple smaller 
transistors in compact modules to replace a larger package.  But, before 
going that far, you likely can find a similar package NOS.  (New Old Stock).

I think the web has a beautiful conversion of a Corsair or similar model 
to a non PTO VFO.  The Corsair has good "bones", and makes a worthy 
conversion subject.

Stuart Rohre
K5KVH

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