[Hallicrafters] SX100 Help

[Jim Liles]

Ray,

Check T6P2 that is the I.F.  output line to the detector.

Check the wiring on the AVC circuit on V7 to verify that it is wired exactly as the MARK 2 manual indicates.   

If you have a signal generator check to see what S-Meter reading produces an S9 reading.

The audio on that radio is excellent.

Kindest regards Jim K9AXN   



  
-----Original Message----- 
From: Ray Keefe 
Sent: Thursday, September 25, 2014 10:35 AM 
To: hallicrafters at mailman.qth.net 
Subject: [Hallicrafters] SX100 Help 

I've got an SX100 Mark2B here. So far I've recapped it, replaced a 
couple of out of tolerance resistors.

Removed and threw away the plug in rectifier replacement after it 
shorted out and almost cooked the transformer. Used a couple of 1N4004 
diodes and a 25watt adjustable wire wound resistor to bring the B+ 
voltage within range of the schematic.  B+is now just about 270+ give or 
take 2 or 3 volts.

It's got distorted audio, had it before I started, believed it was 
caused by one of the defective Black Beauties.

When tuned to a local BCB station 3 miles away, I've got good audio up 
to T5 C76, on my Heathkit signal tracer it sounds fine. At Pin 8 of V7 
it sounds garbled, overloaded, the S meter is also bouncing with the 
modulation. The voltages are good on V7. The audio stage is ok, fed a 
audio signal into the phono line and loud and clear from the speaker. V7 
tested good on both of my tube testers, don't have sub for it. Pulled it 
and the audio was still garbled checking the feed to it with the signal 
tracer.

I've removed a couple of mods that someone had done to the standby 
switch. I've almost ruled out someone mucking with the IF chain, since I 
can hear AM signals all the way up to 10m, weak, but can still hear them 
on the signal tracer connected to the pin 2 on T5. The calibration is 
almost dead on when checked against WWV on 5,10, and 20mhz.

Anybody have any ideas on where to look next?

Tnx
Ray
K2RJK
______________________________________________________________
Hallicrafters mailing list
Home: http://mailman.qth.net/mailman/listinfo/hallicrafters
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Hallicrafters at mailman.qth.net

List Administrator: Duane Fischer, W8DBF
** For Assistance: dfischer at usol.com **


This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html