hallicraft: S-29; Sky Traveler

ID: 299388
? hallicraft: S-29; Sky Traveler 
04.Oct.12 02:17
7

Frank Pascale (USA)
Articles: 14
Count of Thanks: 5

I have restored a Hallicrafters S-29, but sensitivity appears to be less than what I'd expect on the broadcast band.  Making some signal generator measurments (on any band), it takes about 3000 microvolts at the antenna to ground terminal to get a reasonable signal level, and at 1000 microvolts, it is just "hearable".  A signal into the 455kc chain gives a good output at about 100 - 300 microvolts.

I have aligned it per manual instructions (I believe), and the voltages at the filaments and plates of the 1T4 and 1R5 all seem within bounds.

I realize it would be good to know what to expect as a sensitivity for, say, the broadcast band of this radio.  I have not been able to find this figure anywhere. 

Can anyone help guide me? 

Best Regards,

Frank Pascale

Long Island, New York

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 2
AVC 
04.Oct.12 06:19
7 from 1954

Emilio Ciardiello (I)
Editor
Articles: 533
Count of Thanks: 4
Emilio Ciardiello

The problem may be caused by a wrong AVC bias on the RF stage. Try to check R1 for open.

Emilio

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 3
AVC Check 
05.Oct.12 00:05
51 from 1954

Frank Pascale (USA)
Articles: 14
Count of Thanks: 4

Emilio:

Thank you for your guidance.  This will be a good weekend investigation!

Best Regards,

Frank

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 4
S-29 Low Gain 
25.Oct.12 01:24
132 from 1954

Frank Pascale (USA)
Articles: 14
Count of Thanks: 4

Emilio:

R1 turned out to be about 1.7 meg and the schematic called for 2.0 meg, so it wasn't open.  But you set me on a course to rule out AVC, as the voltage seemed to vary as the stronger stations were tuned in.  As I was looking there, I became troubled by a free wire I had disconnected from the metal cabinet when I removed it from its case.  Looking closely at the pictures I had taken before disassembly, this wire went directly to the metal cabinet, and was actually "returned" to the chassis by a 0.05 capacitor.  Now it was floating.  It connected to the low end of the bank of coils in the RF stage.  Grounding it to the chassis (it is being operated on an isolation transformer), returned the sensitivity (about 30 to 100 microvolts for good quieting).  Thanks for making me look closely at this.

Best Regards,

 

Frank

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