Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Aug Tue 03, 2021 1:40 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 42 posts ]  Go to page Previous  1, 2, 3
Author Message
 Post subject: Re: Hallicrafters S-40B- Audio Completely Dead
PostPosted: Jun Fri 18, 2021 1:39 am 
Member
User avatar

Joined: Nov Mon 02, 2009 7:01 am
Posts: 5321
Location: Lincoln City, OR 97367
Greetings to Forrest and the Forum:

Unless you are probing high voltages (in excess of 300 volts or so) you do not need to isolate your scope probe with a capacitor.... and doing so will adversely affect the calibration of the scope. (Be sure to use a X10 probe.) The scope sweep speed should be set to display the audio frequency waveform. The RF carrier will then look like a bar of light of varying height; the RF oscillations will be too fast to be seen.

Here's a diagram of what you should see:

Attachment:
am-modulated-wave.jpg
am-modulated-wave.jpg [ 74.33 KiB | Viewed 159 times ]


50 mSecs per division is a bit slow. That would display an audio waveform of 20 Hz.... but your signal generator is more likely modulated with a tone of 400 or 1000 Hz. I would try a sweep speed of .2 (2/10) of a millisecond per division. You should then see a waveform more like the illustration.

Regards,

_________________
Jim T.
KB6GM


Top
 Profile  
 
 Post subject: Re: Hallicrafters S-40B- Audio Completely Dead
PostPosted: Jun Sun 20, 2021 4:18 pm 
Member

Joined: Oct Tue 17, 2017 8:25 am
Posts: 47
I just wanted to jump in here really quick to apologize for my lengthy delay since my last message. We have family coming over for my mother's birthday and Father's Day in a few hours, and have been preparing for their arrival for a few days.

I will send pictures of my oscilloscope in tomorrow or the next day.

Thanks,
Forrest


Top
 Profile  
 
Post New Topic Post Reply  [ 42 posts ]  Moderator: Sandy Go to page Previous  1, 2, 3

All times are UTC [ DST ]


Who is online

Users browsing this forum: k9uw and 13 guests



Search for:
Jump to:  


































Privacy Policy :: Powered by phpBB