[Johnson] Old Resistors

[Jim]

This is a well documented issue.
The older carbon resistors tend to drift high in a radio or in the Junke 
Boxe.

Jim


>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