The Oscillator Mixer

[ElectricSparq]

Hi,

Is there a sovtek equivalent for the 12sa7?

Thanks for the video.

[AllAmericanFiveRadio]

@ElectricSparq

I did not see one listed.

[pozitroniac]

WONDERFUL AND SO INSPIRING..IT HELPED ME TREMENDOUSLY IN UNDERTANDING THE CONVERTER STAGE ..SO MUCH TO THE EXTENT OF TURNING MY GRANDMOTHERS DUSTY AND RUSTY DEAF RADIO INTO A SINGING LOUDLY NIGHTINGAIL...IAM VERY GRATEFUL TO YOU...MANY THANKS FOR BEING SO INFORMATIVE AND SUCH A CALM AND INTEGRATED PERSONALITY...HAVE A NICE DAY...

[AllAmericanFiveRadio]

Thanks pozitroniac

[mamoynas]

nice video... the link is Redirected though...

[AllAmericanFiveRadio]

Thanks mamoynas

And thanks for letting me know about the link. I changed servers and I knew I would not find all my YouTube links. This one now works.

[sloppyoscar]

thanks for another informative video! You mention that points A and E are in phase. Normally the polarity is switched between primary and secondary but my guess is that they are wound in different directions to achieve an in-phase relationship?

[AllAmericanFiveRadio]

Thanks sloppyoscar

Yes it is wound so that is it in phase or they reverse the leads to put it in phase. But it must be in phase for positive feedback.

[29riteshkakkar]

nice one....

[AndyDaviesByTheSea]

Hi Rick, thanks again for the video If you run to 2 minutes 23 seconds where you discuss R2, is there any significance for connecting the earthy end of R2 to the top of L2? Could R2 have simply been connected to ground, or would that sort of decision been made on the assembly line where it may have been more convenient to solder R2 across the valve holder?

Or is there some interaction between the cathode and grid against the resistance / impedance of L2 that I'm missing?

Kind Regards. Andy

[AllAmericanFiveRadio]

@AndyDaviesByTheSea

Maybe. The only way to find out is to move it. But I don't it would Oscillate as strong.

[ksolo1007]

Hi, great video.I am studying the rf mixer stage and most text books do not get into the actual wiring of the mixer coil. To really get this circuit I suggest to take a few coils apart from a junk radio and see how the coil is constructed.This is where the magic really happens with the magnetic fields moving electrons! Thank you!

[uploadJ]

Ah! A "pentagrid converter" like a 6BE6 and 12BE6 tubes as some of us learned in school!

Great series of vids!

[AllAmericanFiveRadio]

THANKS!

[Agrajag042]

This is a really good video. Could you possibly do one on the regenerative and super regenerative receiver?

[AllAmericanFiveRadio]

I was going to talk about the regenerative circuit on my Crosley Pup video but I could not find a wiring diagram for it. However I found my Deforest-Crosley model 51, it is a regenerative circuit and I have the wiring diagram. I have not fired this radio up in years so if I can get it to work I'll do a video on it soon. The regenerative and super regenerative receiver circuits are very similar. The super usually has more tubes and better regenerative controls.

[CameramanLink]

That's a really nice, thorough explanation. I feel enlightened about the finer points of mixer and heterodyne operation. I do have one question: why was there some distortion on the top oscilloscope trace?

[AllAmericanFiveRadio]

Figures, lol.

Good question. The 12SA7 is doing multiple jobs, the tank circuit in the primary of the 1st. I.F. and the tank circuit in L1 & C1 are causing the distortion. L2 is just a coil and it has no capacitor across it to smooth out the wave-form and of courses you can't put one there because you would have another tank circuit. And Thank!

[CassetteMaster]

That's a neat and very well-done video!

[AllAmericanFiveRadio]

Thanks.

The AC bias in your cassette records also uses a tank circuits mostly. If you have a wiring diagram for your recorders, that coil that you identified in your AC bias video, should have an in-phase connection from the coil to the base of the transistor associated with the AC bias circuit, it can be incorporated with the erase head.

[joernone]

Rick,

As always, a superb video. Detailed technical explanation and use of graphics are extremely well done. I'd rather watch one of your videos than go to the movies...and I love Indiana Jones and Iron Man.:)

Regards,

John

[AllAmericanFiveRadio]

Thanks John,

I have lots of drawing, photography, and publishing software tools that I used for jobs and my books. Had no idea, when I bought them, how great they would work for YouTube videos.

Regards

Rick

[cyberlightbeing]

Great video - many thanks, I really like your explanation & circuit analysis, please do more. One question if I may (sorry if it sounds so basic) why is the 455KHz was choosen as an IF freq for AM radios?

[AllAmericanFiveRadio]

Thanks, and I'll keep trying.

HO, that's a very good question, and there are a number of reasons. The early radios by different manufactures use many intermediate frequencies, like about 175KC, and notice that this is an odd harmonic. If for some reason there are broadcasts using 175KC it would always interfere with the operation of that radio.

[AllAmericanFiveRadio]

Also the higher the intermediate frequency, the more audio information can be carried, resulting in higher quality audio. The FCC cleared 455KC, no broadcasting allowed, it's an odd harmonic, and all AM stations are even harmonics which also helps to eliminate other problems.

[Hammondlover2]

More gold from the mine. Which radio's schematic did you use for this example? It looks familiar.

[AllAmericanFiveRadio]

Ho wow thanks.

This wiring diagram is from the RCA radio model 9X571. It is a very typical design and many other manufacturers used a close cousin to it.