[Swan] 250C

[Ken Sands]

Collin,
It seems your trouble is the mixer. Get an original schematic and put in
the original mixer tube. A mixer has very little "gain" if designed
correctly.
Also check the injection voltage  from the first conversion oscillator, 
it should be substantial 1 volt or so going into the mixer grid.
Resistors are notorious for changing value over the years, take each one
loose on one end around the mixer and check its value...+-10-20%.
Capacitors also leak DC into tube grids changing bias levels and must be
replaced in critical circuits like mixers.
I suggest you contact Land Air Communications on the net. Dial 
718-847-3090 and give Hal K6DPZ a holler. He has seen it all and is a
real nice man. He repaired my Collins KWM-380 for me.
73, Ken K8TFD 
On Fri, 03 Aug 2007 21:48:54 -0400 n4tua at aol.com writes:
> Dear Friends,
> May be getting closer but seems like I am going in circles. I went 
> back 
> and did sig gen testing on the 250C again starting from the mixer 
> plate 
> working back toward the antenna. At the mixer plate I get a good S9 
> 
> signal with 5uV at 10.9mhz. Then when I moved to the grid of the 
> mixer 
> expecting a stronger signal indication with less sig gen input. But 
> no 
> just the opposite. For some reason the mixer does not seem to be 
> amplifying. I have checked all voltages and resistances associated 
> with 
> this triode tube (6HA5) which has been subbed with a 6HM5. These are 
> 
> the same electrically, but??? Once again I am scratching my head.
> Collin
>
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