Thankyou!! You're quite a teacher. I've been studying all weekend in preparation of a new Eico 369 sweep generator and getting my arms around where to inject and take off the signal. This video nailed it. Thanks for all your work.
Thanks for the vid, I'm still learning (trying) to follow the signal through the schematic. Really appreciate that keep things as basic as the subject will allow and also that you don't rush through. Thanks again, Stan in SC
Thanks so much for showing all the detail in the schematic on voltage checking. I'm still learning, so this video was most helpful. I know these videos don't just shoot and edit themselves- there's a lot of time, effort and labor that goes into producing something like this. This is an older video, but the information is still very valid. Regards, Tom
Thanks radioland1 Hey Meyer, I'm happy that this video helps you understand FM radio. This video is the result of your question about FM. And I know there are other RU-vidr who are very interested in FM circuits. Thanks for your question and it is neat to make another friend in Brazil. Rick
My oscilloscope has an impedance of about 10megs. So if a circuit is also 10megs, the scope will drain half the power from the circuit. If the circuit under test is 100megs, then the scope will pull it down about ten times more.
@CameramanLink I figured you did. I am fascinated with the discussion, if the ratio detector or discriminator is better. When both rely on the same frequence shift from center to work. The real difference is/was Sarnoff lawyers and Armstrong lawyers.
@joernone Thanks John, It would be better to use a tube tracer. This solid state tracer seems to be design will, but I would want to use it on big power transformer radio. Regards, Rick
Thank you. After taking it apart, the vol pot is not really accessible .i am now thinking of building an FM transmitter to hook the microphone up and transmit through that.
Thanks CameramanLink AA5 and FM was invented by the same guy, Edwin Howard Armstrong. You know about AM. FM demodulation relies on frequency shift off center of the 10.7, the intermediate frequency. It is the LEVEL of the frequency shift from center that is rectified producing the audio. Interesting isn't.
Your microphone would have have a fairly high output. You could try connecting a microphone across the volume control, but it doesn't look like your radio has a pre-amplifier.
Rick, Thanks. This was a really good vid...opening my troubleshooting eyes even wider. And as usual, your use of instructional aids was superb. Wish I could do even half that well. Your signal tracer is solid state. Aren't you afraid it'll be fried? How much voltage can it take? Regards. John
Interesting video, but there is one thing I don't understand. How is it possible for measuring instruments (like an oscilloscope) to short out the signal? The inputs of scopes are high impedence, so that they should not interfer with the circuit under test. How can e.g. a 1 MOhm input impedence short out anything at all? Also, I noticed the scope didn't short out the signal anymore after the demodulation stage. How come? Thanks for all your videos.
Another big chapter in radio repairing. Could you tell me something about your signal tracer? I understood there are two modes: rf and af; is it correct? Wich is the differece inside its circuitry?
Hey, Rick You know I dig your videos, and always learn new stuff. But really, I've got to say, I just want to go through all your stuff and rifle through your parts and junk drawers. Is it ok to say that? Oh well, I already said it! And... I need to find an old O scope that's going for $5.00. Not asking for much am I?!
Thank you for this This may be a bit of a dumb question but what is the difference or advantage between having an oscillator tank circuit or an oscillator vacuum tube Thanks
The tank circuit is the resonant frequency part of the circuit. The vacuum tube supplies enough enery to the tank circuit to keep the entire circuit oscillating. Positive feedback. The Oscillator Mixer ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-d96vwarHcsg.html
Ah ok thank you. I think what confused me is that perhaps some radios. (Maybe older ones) will have 2 separate tubes for this. One for the oscillator and one for the mixing where some radios will have it on in one tube?
@@alexinnewwest1860 The higher end radios and military radios usually have a separate oscillator tube. Making the radio more accurate and stable, but more expensive.
I have a different question for you. I have a Aiwa CSD-MR1 that I would like to hook a microphone to so I can play through the amp circuit. Do you have any suggestions on where I can connect the mic input?
The radio that is under test is always on my isolation transformer. The oscilloscope ground and the radio ground are connected together. The points that I tested in this radio are marked with a red arrow and on the wiring diagram you can see the pin number and tube number. In the video is a page of how to count the pins on several tube socket types. This information is also in my free e-book, here is a link to the download page. www.richardmcwhorter.com/vacuumtuberadio/
Hello Jim please excuse what could be a silly question as I have no experience with broadcast receivers and specifications. What do you use a a typical input setup for your RF signal generator. I would typical use 3khz deviation for the narrow band equipment I normal play with. But I see most FM broadcaster receiver specify 1khz mod with 75khz deviation. Have I got this right as my signal generator won’t exceed 20khz deviation but it’s really designed for mobile radio repair Marconi 2955. Is the deviation setting real 75khz. Many thanks regards Chris
AllAmericanFiveRadio hello Jim I don’t have the radio in front of me now but it’s a 1980s kenwood tuner, AM FM stereo. I’m not actually working on the radio as such it’s just that it is the only receiver I have that has a 75 ohm input. I noticed it was picking up my test tone 1khz 100mhz at less than 1uv but sound very scratchy, increasing the signal level did not help. I think the problem could be the deviation of my test set as it only goes upto 20khz. So I’m really just after some typical deviation and input levels you would typically feed into a stereo tuner etc with your test gear. I can find the tuner info later but it’s not really a question specific to the tuner. I think the problem is probably with my signal generator in that it’s not designed for stereo or the deviation level etc. I will find a link to my previous tuner video. Many thanks Regards Chris
hi rick, i have a question that is not related to this video. i have to replace some capacitors on an amplifier but the amp was made in sweden and uses roe brand capacitors that i think were made in germany. these capacitors are not labeled like normal capacitors. one says 10/63 another says 22/63 and the last says 47/63. does this mean 10mf/63volts etc? they don't look big enough to handle 63volts so i am kind of guessing it means 6.3v maybe . please explain these numbers to me, thanks.
Does having a negative voltage on the grid clearly prove that the oscillator is running? What if a Schematic calls for 7 V negative but you have 4 V negative what was that suggest?
AllAmericanFiveRadio In your video you mentioned that checking at the oscillator tube is often impossible. So would you suggest checking it farther down the chain? That seems fine but if one of the I F stages are inop it would be inconclusive right?
