Thanks. I have found that the AVC circuits in the early radios are more similar than they are different between manufacturers. I hope the video will help!
Seeing this video reminds me that I do infact have something about AVC hiding in a remote part of my mind. Must have read about it in school och somwhere on the net many years ago. Thanks for this awesome hands-on demo! Ingenius invention I must say!
I know this is a pretty old video, but I just found it when looking for information about how to find the AVC line on my ZTO H500. You provide a very clear explanation of how to find it and how it works. Thank you so much.
AVC is useful for tape recorders, for recording it would be a Automatic Level Control. Very similar ideas. When things get quiet the gain increases. The AVC in radios is evening out the volume of strong and weak stations.
@IBreedBassetts9C The diode in the 12SQ7, pin4 and the cathode, changes it to DC. Current can only flow when the plate, pin4, is positive. When the top of the coil is negative there is no current flow, so that part is discarded.
To disable the AVC you use the smallest usable signal possible. You don't want the .05uF 12.11 capacitor, the one at the bottom to change up. If it charges up and it will be negative, that charge will lower the volume making it harder or impossible to find the I.F. peaks. Thanks!
As always, your videos make theory interesting and easy to understand. I have always believed that knowing theory is the key to successful troubleshooting in terms of quality time used to complete a repair as well as completing it professionally. Thanks and keep your videos coming.
Thanks. YES, they could have use the positive half, but that would make the bias positive on the grid making the tubes conduce more. Just the opposite of what is needed.
Hi..I have a Hallicrafters SX-71 and Im trying to find the AVC control..is it part of the BFO switch? The diagram seems to show it this way, and how would the avc work on this receiver..? I am new to aligning radio's..but have some background in electronics..your videos are great...very laid back, but to the point videos..thanks..
Thanks. I have found that the AVC circuits in the early radios are more similar than they are different between manufacturers. I hope the video will help!
Took a while and it has fallen into place for me. Your explanation is great. Thanks again.
Thank you, and your welcome.
Seeing this video reminds me that I do infact have something about AVC hiding in a remote part of my mind. Must have read about it in school och somwhere on the net many years ago. Thanks for this awesome hands-on demo! Ingenius invention I must say!
AA5,
Awesome AVC operation vid! Now, I know how it REALLY works! You can only get so much from a book!
Take Care,
John Strunck
Es muy bueno poder manejar el punto de control automático de volumen a partir de las primeras etapas de audio.Gracias por la demostración.
+adolfo jose alvarez dolmus
Thanks
Thanks, I think the AVC is one of the more interesting circuits.
I know this is a pretty old video, but I just found it when looking for information about how to find the AVC line on my ZTO H500.
You provide a very clear explanation of how to find it and how it works. Thank you so much.
AVC is useful for tape recorders, for recording it would be a Automatic Level Control. Very similar ideas. When things get quiet the gain increases. The AVC in radios is evening out the volume of strong and weak stations.
@IBreedBassetts9C
The diode in the 12SQ7, pin4 and the cathode, changes it to DC. Current can only flow when the plate, pin4, is positive. When the top of the coil is negative there is no current flow, so that part is discarded.
To disable the AVC you use the smallest usable signal possible. You don't want the .05uF 12.11 capacitor, the one at the bottom to change up. If it charges up and it will be negative, that charge will lower the volume making it harder or impossible to find the I.F. peaks. Thanks!
Thanks! It is very interesting how similar the two circuits are, and also interesting what the differences are. But they both work very well.
I'll have to look at the Magnavox diagram to see what to check. And Thanks.
Thanks John. I always thought the AVC was interesting and of course very useful.
Thanks, it is a very interesting and useful circuit. Important to know about when aligning radios.
that schem u showed, starting off, looks like a SUPERHET :)
As always, your videos make theory interesting and easy to understand. I have always believed that knowing theory is the key to successful troubleshooting in terms of quality time used to complete a repair as well as completing it professionally. Thanks and keep your videos coming.
88jolzenrocket Thanks
Thanks.
Not yet, but you can download my book for my RUclips Channel.
VERY GOOD INFO......
Thank you and your welcome.
Sure.
Yep it is a superheterodyne.
So the negative voltage actually comes from the negative swing of the signal , been struggling with this concept for many moons, thanks.
Thanks.
YES, they could have use the positive half, but that would make the bias positive on the grid making the tubes conduce more. Just the opposite of what is needed.
i never knew there was such a thing as a triode?
thnx :), can this be tuned to pick up low signal 675 kHz?
Just wondering how a ground can be positive in the circuit. Is it just because you have a negative dc voltage that can't pass through the .05 cap?
+Cameron Burns
If you were to reverse the diode, then you would have a negative.
Hi..I have a Hallicrafters SX-71 and Im trying to find the AVC control..is it part of the BFO switch? The diagram seems to show it this way, and how would the avc work on this receiver..? I am new to aligning radio's..but have some background in electronics..your videos are great...very laid back, but to the point videos..thanks..
This set has an AVC switch SW38 the AVC capacitor is C50 0.05MFD
It's SW3B not SW38.
SW3B is the AVC switch, SW3A is the BFO switch, the dotted line between them means they are mechanically linked together.
So the AVC is working when the BFO switch is in the OFF position..is this right..?? Thanks for your help
Yes R48 disables the AVC
Thanks alot..just curious if you were a teacher...you have the patience and voice of one...
Typo! och = or ... don't know how I managed that.