Hallicrafters RXer on an old Airforce one plane (JFK)

[WQ9E]

Clark,

Hallicrafters suggest you install this in the B+ feed to the first RF amplifier tube.  There is a misprint on the schematic, the tube is labeled IF instead of RF but the rest is correct.  The meter has to be installed in an AGC controlled stage so that it reads a plate current which varies due to signal level.

I would suggest putting a pair of diodes across your meter terminals which will help to protect it from certain circuit failures.  In normal operation, there is not enough voltage drop across the meter coil to "fire" the diodes but if high current flows through the meter the diodes will shunt this and generally protect the coil from burnout.  This, of course, is applicable to the internal meters also and not just your external one.

Nice find with the meter, they don't show up that often.  I think the most popular demand for the external meter was to go with the S-20/S-40 family of receivers. 

I always thought the SX-62 would look nice had they designed a "magic eye" tube into the receiver.  If I ever come across a real junker I may try it.

Rodger WQ9E

[ke7trp]

Thanks for the info. I think that is what confused me.  Which tube is the first RF? 

Clark

[WQ9E]

Clark,

The first RF is the 6AG5 tube at the left rear corner of the receiver (your left looking from the front).  But for installation, you need to insert your meter into the point in the feed that is "cold" for RF.  So open the B+ lead at the end of R-7 NOT connected to C15 and that is the proper place for the meter leads.

Rodger WQ9E

[ke7trp]

Thank you for the help. I am not sure why this is confusing to me but it is.  The meter is going to bridge that connection? The B+ side of the meter goes to R7 away from C15. The Neg side of the meter goes to where R7 was connected?

Clark

[WQ9E]

You are welcome Clark. 

Within the meter case you should have an 82 ohm resistor connected to the negative terminal of the meter and a 500 ohm pot with the wiper connected to the positive meter terminal.  One end of the 500 ohm pot is connected to the other end of the 82 ohm resistor.  The terminal where the 82 ohm resistor and one end of the pot are connected should be connected to the "non-C15" end of R-7 and the B+ lead that was connected to R-7 now goes to the positive terminal of the meter which is also be connected to the wiper contact on the meter zero pot.

Make sure that this adjustment pot is in place and I would disconnect the wiper end from the meter terminal and check the pot continuity to make sure that it is not open.  If the 500 ohm pot (acting as a meter shunt) is open then the full plate current will flow through the meter coil-a good reason why you want to put the diodes across the meter terminals to prevent burnout in case of component failure.

Rodger WQ9E

 

[ke7trp]

Thanks alot sir.  I really appretiate you laying this out for me.  I am going to wire it in tomorrow.

Clark