[Hallicrafters] SX-42 Help Needed

[Rodger]

Joe,

The first RF stage is not used on the broadcast band range so if you 
were testing here that would explain the weak signal when injecting 
there.  If it is still weak when the signal is injected on the 2'nd 
through 4'th ranges then that might point to a problem in your first 
stage/input.  Is the link connected between A2 and A3 (assuming you are 
not using a balanced feedline)?

On the 2'nd through 4'th How much signal and how were you injecting it 
on the grid of the 2'nd RF stage?  If you loaded it down with you 
generator output impedance and reduced the bias or fed too much signal 
this would cause the distortion since the grid impedance is quite high.

Does turning the AGC off have any effect on the weak AM signals? 

If the 1'st RF stage is still a problem on bands 2 through 4 carefully 
examine the back wafers on the bandswitch for burnt contacts and signs 
of arcing.  This portion of the switch is prone to arcing and carbon 
tracks due to the plate voltage present on it.

Rodger WQ9E

 Joe Connor wrote:
> Well, I picked up the SX-42 and it was as advertised: strong on FM but weak on AM. I did some signal injection. 
>
> On the lower four bands, a 455-khz signal injected into the 1st IF gave strong output. An RF signal on the plate of the 2nd RF gave strong output. An RF signal at the input of the 2nd RF gave distorted output. An RF signal in the 1st RF gave weak output. The volutages in the 1st and 2nd RF test normal.
>
> Where do I go from here?
>
>                          Joe Connor
>
>
>       
>
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