[R-390] Low Audio

[Flowertime01 at wmconnect.com]

Frederick Bray wrote,

I measured the diode load and have over -30 volts on both AM and with the 
calibrate/bfo, depending upon where I set the RF gain control.  I pulled 
the hoods on both of the cables to the AF deck and could not find any 
broken /lose wires.  Guess its time to start measuring things in the AF 
deck.

Thanks.

Fred

------------------------------
Fred,

>From the diode load the signal goes back into the IF deck and to the limiter 
V507. The tube is a 5814.

Turn the local gain all the way up. 
As you turn the limiter on and off you should hear a pop or click in the 
audio output as the limiter tubes goes into conduction when turned on. 

>From V507 the signal goes to the audio deck and V601. The tube is again a 
5814 and both sides of it are used as audio amps. The signal out of V601 goes to 
both the line gain and the local gain controls on the front panel. You should 
be able to hang an AC volt meter on the controls and measure a small AC signal 
when you have a good AM station or Cal tone and BFO on that pegs the carrier 
meter. 

If you have AC signal on the local and line gain controls that you can very 
in voltage by changing the RF gain control, the you are good to that point. 

If you do not have a measurable AC signal on both the line and local gain 
controls, you will have to explore V601 in the audio deck or V507 in the IF deck. 
You also need to keep the wire harness in mind as you are exploring. Do an 
eyeball on the 5814s to ensure you filaments on both side of each of the tubes.

The wide sharp audio response switch is associated with V601. You may need to 
explore this switch behind the front panel for a problem. When you dropped 
the front panel to clean the other controls, you may have the wide narrow switch 
and wiring giving you problems. It may have seen you working on the other 
controls and feels a need for a snit as it was being ignored.

Roger