[Hallicrafters] SX-25 Troubleshooting Help Needed


WA1KBQ at aol.com WA1KBQ at aol.com
Sun Jun 26 09:08:20 EDT 2011


Difficult to troubleshoot when you have original parts which most are  
likely degraded (capacitors act like resistors and resistors have drifted  
upwards in value over time). A radio not working properly will always show up in  
out of spec tube pin voltages. You will need to check them starting with  
the RF stages and work toward the audio. Pay close attention to grid #1 
voltage  with respect to the cathode. To quickly find a stage not working  touch 
the control grid of each stage from RF forward and it should produce  a loud 
buzz in the audio. You can touch them with the tip of a  soldering iron if 
you don't want to use your finger.
 
Regards, Greg
 
 
In a message dated 6/24/2011 8:43:38 P.M. Eastern Daylight Time,  
joeconnor53 at yahoo.com writes:

I picked  up a beat-up SX-25 today and need some help.

After changing the  'lytics, the broadcast band (Band 1) plays beautifully. 
The set,  however, is completely dead on all other bands. There isn't even 
static.  There is no sound when I disconnect or conntect the antenna. 
Jiggling the  bandswitch does not help. I have plate and screen voltages on both 
the 1st and  2nd RF tubes (6SK7s). 

I did signal injection. On Band 2, I  got an RF signal from a signal 
generator through the 2nd RF with some  amplification. (Thanks God for tube 
extenders!). I got an RF signal  through the 1st RF with no amplification. Even 
the amplification I got on the  2nd RF was far less I got on Band 1 (BCB). On 
Band 3, I couldn't get any  signal through either RF stage. 

The set is pretty original.  There are signs of a few caps being replaced 
in the '40s or '50s. The only  modern cap is one orange drop used as a bypass 
cap. I'd like to  troubleshooting this systematically, rather than simply 
blindly replace caps  and hope I hit the problem.

Any ideas or troubleshooting  tips?

As always, thank you for your  help.


Joe  Connor
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