[Premium-Rx] Racal Receiver OCXOs

[Stein-Olav Lund]

Hi Dan and group,
Thanks for good info and a copy of the 9442 schematic!
I replaced this TCXO from a Neuwirth radio test set,
seems as  many used the Racal-Dana TCXOs. Mine jumped in frequency like you described. I found one on eBay which I put in a couple of years ago.
I desoldered the 30pF cap and measured it in a cap tester while
heating with a hot air gun. 
Almost at once the capacitance jumped down to 24pF, after removing the hot air it jumped back to nominal! So this blue beast clearly is a dud!
Replaced it with a Philips NPO 33pF, was able to adjust up to 5000.00kHz (barely)
Seems it's stable now!

Happy Holidays from Trondheim
Stein-Olav Lund, LA9QV



-----Opprinnelig melding-----
Fra: premium-rx-bounces at mailman.qth.net [mailto:premium-rx-bounces at mailman.qth.net] På vegne av Michael O'Beirne
Sendt: 16. april 2011 22:11
Til: danrae at verizon.net
Kopi: PREMIUM-RX
Emne: Re: [Premium-Rx] Racal Receiver OCXOs


Dear Dan

The 9442 Racal-Dana standard is known for failure.  I had the same problem. 
In the end Pat McA G3YFK sent me an ITT TXCO (that fits on the BFO board 
from memory) and it does all I require and has fully satisfactory stability, 
both short term and long term.

73s
Michael
G8MOB

----- Original Message ----- 
From: "Dan Rae" <danrae at verizon.net>
To: <premium-rx at mailman.qth.net>
Sent: Saturday, April 16, 2011 5:34 PM
Subject: [Premium-Rx] Racal Receiver OCXOs


>I have just repaired the second 9442-12 rapid warm up oven to have
> failed in an RA1792 here.  One might not be a cause for concern but two
> going worries me :^)
>
> In both cases it was the ceramic (?) capacitor that is in parallel with
> the trimmer that failed or changed value.
>
> In the first one the fine wires that lead from the PC board to the base
> had PVC insulation that had hardened and gone brittle as well.  The
> second one seems to have PTFE covered wiring.
>
> I have spread it around a bit already but I do have a rough circuit
> diagram of the thing if anyone is faced with the same problem.
>
> Dan
>
> ac6ao / g3ncr
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