[Johnson] Old Resistors

Carl km1h at jeremy.mv.com
Tue Apr 3 08:31:41 EDT 2012


Thats common with a few brands of resistors. I see 47K screen resistors in 
Nationals well into the megs fairly often as well as 10X-20X changes in 
other gear.

OTOH a first run after WW2 NC-240D and a last year 1961 Viking II CDC didnt 
have a one out of tolerance.

Blame it all on the purchasing departments and managements money saving 
controls. National changed management shortly after and bought the cheapest 
they could find. I remember having to replace many even in the mid 60's.

Carl
KM1H


----- Original Message ----- 
From: "David C. Hallam" <dhallam at knology.net>
To: "Johnson List" <johnson at mailman.qth.net>
Sent: Tuesday, April 03, 2012 7:34 AM
Subject: [Johnson] Old Resistors


>I ran into an interesting situation yesterday.  I was finding multiple
> spurious signals when I tried to zero beat a received signal with my
> Invader 2000.  I put it on the bench to find out why.  It turned out to
> be a carrier oscillator problem.  The unused oscillator was not being
> turned off so the carrier frequency was a mix of both the 9001.5 and
> 8998.5 KHz frequencies.  The cause was both of the grid dropping
> resistors on the 12AU7 oscillator were WAY out of spec and insufficient
> bias was applied to cut off the unwanted oscillator.
>
> The resistors are supposed to be 820K.  One measured 3.2M and the other
> 4.1M.  Has any seen old resistors go this high in value?  This makes me
> wonder how many other resistors in this thing have a similar problem.
>
> David
> KW4DH
>
> -- 
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