Re: {Collins} 51S-1

Hi Bill and fellow Collins Collctors.
In My 75S3B I found a 7543 in my Dad's Tubes from
30 Years ago. With the 7543 the PTO is SO stable.
The drift from Cold to warm-up is almost not
Noticable. The 6AU6 was not bad but that
7543 is just Great.
Also since I am using the Receive PTO on my
32S3, my Transmitter is just as stable.
                      Stan K6RMR

The inter-electrode capacitances are often different in the "Industrial
Strength" versions of tubes, so watch the alignment when using this kind of a replacement. My take on this, Collins chose the 7543 for its more robust
(and thus physically more stable - good in a PTO) construction so I would
stick with the 7543.

Bill Carns, N7OTQ
Trustee K0CXX
President, Collins Collectors Association
Editor, Signal Magazine
Wimberley, TX
512 618 2762  (Cell)
512 847 7010  (Home)

-----Original Message-----
From: Collins [] On
Behalf Of Rick Poole WA1RKT
Sent: Thursday, November 20, 2014 6:46 AM
To: collins
Subject: Re: {Collins} 51S-1

Good morning, Steve.

Per a Sylvania data sheet dated April 1960 (google "6AU6 7543"):

"The Sylvania Type 7543 is designed to provide low hum, non-microphonic
operation through the incorporation of a helical wound heater and rigid
mounting of the internal components. The 7543 is otherwise similar to, and
a replacement for, the Type 6AU6.".

So, I'd say the 6AU6 should work fine.

Londonderry, NH
Catch me on 14.300 MHz Intercon / MMSN most days

----- Original Message -----
From: "Steve Wender" <tobiebw2@xxxxxxxxxxxxx>
To: "collins" <collins@xxxxxxxxxxxxx>
Sent: Wednesday, November 19, 2014 11:58:06 PM
Subject: {Collins} 51S-1

Hi All,

I am trying to bring a 51S-1 back to life.  I have tested the tubes and
found many showing shorts and I replaced them. The 7543 oscillator tube is
also showing a short and I replaced it with a 6AU6.  How bad is that?  It
seems to work.  Should I bother buying a 7543?  They don't seem too
expensive. What are your thoughts?


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