RCA 8-X-541 - Cause & Effect P5 (Oscillator Troubleshooting Tips & Common Failure Points)

Looking at the Front-End of RCA 8-X-541 briefly then jumping right into the Oscillator circuit. Common failure points and troubleshooting steps are presented.
Don't miss how to accurately measure Grid voltages using your high impedance DMM at: • RCA 8-X-541 - Cause & ...
A circuit you may find helpful below.
Oscillator Sniffer | Close Proximity AM Transmitter | Ferrite Antenna Booster
• Oscillator RF Sniffer ...
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#restoreoldradios

[@davido.hamilton3254]

I wish to say as well Don...I am impressed that you reply to every comment. That must be a 'huge task' in itself. Also, I have been instructed by many electrical instructors in my 68 years of life, and I personally love your use of 'circles' as you highlite the area of a schematic. It holds our attention to the components being discussed. Fabulous job!

[@RestoreOldRadios]

Thank you. I try to reply to all, but at times life gets in the way. The circles don’t work for all based on feedback I’ve re received, but for me I’ve always found them helpful with busy charts, schematics or alike. Thank you again for your kind words. Best, Don

[@seantonnesen1636]

Thank you so much for taking the time to instruct us on the oscillator circuit and how to troubleshoot it. I always have trouble understanding these circuits.

[@RestoreOldRadios]

Sean, you are welcome. It’s a great reference for me too as time passes. Thanks again and all the best. Don

[@davido.hamilton3254]

Fabulous video Mr. Don. Bless Your Bunions! Good Health To You!

[@RestoreOldRadios]

Thank you for the kind words and I’m glad you found it helpful. All the best. Don

[@mikeerstad3705]

Thanks for the video....I'm expecting a Stromberg Carlson 320H tomorrow.....fella says he thinks the OSC. isn't working.....so with your explanation of how it works.....hopefully I can bring it back from the dead.....

[@RestoreOldRadios]

Hope you’re successful and have it playing again in short order. Best, Don

[@OIE82]

That helps. Thanks for the different test methods.

[@RestoreOldRadios]

Glad you found it helpful and I appreciate your feedback. All the best. Don

[@Backtothefutureradios]

Good stuff Don! I know my first go to is “tube wiggling” lol....you explained that very well and easy to understand! Take Care-Larry

[@RestoreOldRadios]

We all do that and I didn’t even mention it. Thanks for watching Larry and your feedback on the content. Still pouring rain in NC. Best, Don

[@Backtothefutureradios]

RestoreOldRadios off and on rain here...can’t get good wx for cabinet work...I want to try and finish this Airline soon....I have an AA5 (Stewart Warner 13 5U2) on deck....Take Care-Larry

[@wouldchuck3619]

You have done a great job on this series of videos! Great real world demonstration of theory and schematic troubleshooting. Keep up the good work!

[@RestoreOldRadios]

Thanks, will do! I appreciate your positive words. Best, Don

[@jimnewman5596]

The tips were amazing Don, I learned a lot about the oscillator section today, thank you for sharing this great information.

[@RestoreOldRadios]

Jim, I’m glad you found it added value and I appreciate your feedback. Best, Don

[@hestheMaster]

Fantastic learning video on front end and oscillator circuitry as well of an AA5 radio. Never seen this demonstrated on YT anywhere. Thanks for the educational tips Don!

[@RestoreOldRadios]

I really appreciate it. It's been fun going through the circuit and it's been equally educational for me too. Thanks again. Best, Don

[@td7456]

Great presentation, Don! The mystery of how to check the oscillator explained with great detail! Thanks again!

[@RestoreOldRadios]

Thank You Tim. Oscillator circuits can be mysterious and intimidating at times, but just a few check points can usually get you to the root cause. Best, Don

[@ianbutler1983]

Don, This series is invaluable to me. The oscillator in superhets has always been my weak spot, and you cleared up several things with this video. Thanks for all you do for us, Ian

[@RestoreOldRadios]

Ian, I appreciate you watching and your feedback. This series has been fun and educational for me as well. Best, Don

[@shyammohabir8283]

Thanks Don! I learn a lot about antique radios and oscillators!

[@RestoreOldRadios]

Shyam - you’re welcome. I’m glad you found it helpful and thanks for watching and reaching out. Best, Don

[@YouAllKnowBob]

Excellent series! Lots of good tips.👍👍

[@RestoreOldRadios]

Thank you Bob. The videos will be a great resource for me too. It’s hard to recall all of this at times the older I get. Thanks again. Best, Don

[@RestoreOldRadios]

Wonder how the 1megohm trick to lower capacitance loading would work on the RF probe?

[@YouAllKnowBob]

You'll have to experiment and let us know.🤔

[@Theoobovril]

Top video by you yet again Don, these instructional videos of yours really enhance our understanding of the various sections functions of a receiver.

[@RestoreOldRadios]

I appreciate it. It’s been enjoyable putting this series together. Best, Don

[@henkw1562]

Very good tutorial about troubleshooting the oscillator circuit. The theory about oscillators can be very daunting but can be found easily on the net. I am glad that you stick to the radio's circuit. Good tips about troubleshooting and what to look for. I am also glad that you use a multimeter because most people don't have a lot of equipment. Maybe interesting to know what the inductance is of the dipmeter coil for people who want to wind their own as a extra tool. I will following you along. Be safe.

[@RestoreOldRadios]

Henk - I appreciate your feedback. I have a couple VTVM's but really like sticking with the Fluke DMM when troubleshooting. Thanks again for reaching out and your kind words. I'll provide the particulars on the coil ASAP. Best, Don

[@RestoreOldRadios]

Henk - the DIP Meter coil is 756 microhenries. I tried various 1 watt chokes ranging in values from 250 microhenries to 1 milihenry and all worked as well. Of course each will resonant at various frequencies across the local oscillator that spans from ~995 to 2055 kHz. Hope this helps. Best, Don

[@henkw1562]

@@RestoreOldRadios Hello Don thank you for given me the value of the coil. You are right that other coils will work and that only the field strength will differ and will be high at resonance. I will watch your next video's. Thanks for your response. Best regards Henk

[@tinkeringwithelectronics]

Thanks Don, I followed along with you on a Packard Bell 46H, lots of fun

[@RestoreOldRadios]

Glad you enjoyed it Josh. Thanks for watching and following along. Best, Don

[@KetkAiball]

Very nice vídeo Don. I knew that method to watch the wave of the oscillator coil, using another coil as test probe with the oscilloscope, but I had never used it, and had never seen it working before till now. That´s been very interesting for me. Thank you for showing it. Have a nice day Don. Ketk Aiball (Spain)

[@RestoreOldRadios]

Ketk - thanks for watching. It's good to see things visually too, so it compliments DC voltage measurements. Stay well and all the best. Don

[@mmckenzie000]

Another great one Don!! I echo all of the previous positive comments. Thanks for putting this one together!! Mike from Georgia

[@RestoreOldRadios]

Glad you enjoyed it Mike. Let me know if you have that extra 100 ohm resistor in the oscillator circuit when you dive into your... Best, Don

[@mmckenzie000]

Don: my unit has a 120 ohm resistor where you have the 100 ohm resistor. Mike

[@RestoreOldRadios]

Interesting. I need to dig around and see if I can find a documented circuit change. If you run across something on this, please let me know. Best, Don

[@cassvirgillo3395]

Hello Don, Glad you are doing good. Excellent series, presentation and tips. The voice of experience, as I have said before, is the best teacher, and your a great teacher, Thank you for all you do. Looking forward to the next one. Stay well, all the best, Cass.

[@RestoreOldRadios]

Cass, your kind words are motivating and much appreciated. Stay well and all the best to you. Don

[@jdmccorful]

I'll probably watch again, you dropped alot of ques to digest. Thanks

[@RestoreOldRadios]

John - glad it was helpful! It's a future reference for me too. It's hard to recall everything these days for me. Best, Don

[@deanschmeltzer9620]

Thanks Don . oscillator testing is going to be a little easier now. Still a little scary . Can’t wait to try it out.

[@RestoreOldRadios]

Dean - you can do it! Let me know if you need anything or have any questions. Best, Don

[@deanschmeltzer9620]

RestoreOldRadios Thanks

[@zorka4098]

Great explanation with detailed video examples. My kind of tutoring! Keep it up!

[@RestoreOldRadios]

Thanks a lot! Best, Don

[@mohinderkaur6671]

use 1 Meg resistor in series with DMM to isolate it from oscillator

[@RestoreOldRadios]

Definitely works well in this application. Best, Don

[@thome1547]

Dear Don, thanks for this great explanation, it's a highly experienced and practical based specialist talking. I like your video's, thank you for sharing your knowledge. Happy holidays to you and your loved ones, greetings from Germany in these challening times.

[@RestoreOldRadios]

Thank you for watching and reaching out. Happy holidays to you as well. All the best. Don

[@jorge195501]

Thank you

[@RestoreOldRadios]

Thank you for watching. Best, Don

[@migsvensurfing6310]

Awesome troubleshooting series ! Thanks.

[@RestoreOldRadios]

Thank you for watching, I appreciate it. I just published the root cause of the crackling noise. Best, Don

[@charlesst.petersr.6848]

Thanks for info I can fallow and understand... also restore iñg..a farm set with vin.power sup.. keep doing pip..73 N9JNU..

[@RestoreOldRadios]

Thank you for watching and reaching out. All the best. Don

[@cornelolteanu942]

hello sir, if possible I want to know where you can buy the adapter coil for the oscilloscope or how you made it. thank you in advance . all the best !

[@RestoreOldRadios]

I just published a video that shares a method & procedure that can be used at: Designing & Building an RF Oscillator Sniffer Coil w/ X1 (1:1) Oscilloscope Probe kzbin.info/www/bejne/e5fdlp6fpd-NnKc Hope this is helpful. All the best. Don

[@davidlightman3327]

I might put these videos in the EEVBLOG in a video post

[@RestoreOldRadios]

David - thank you, I appreciate it. All the best. Don

[@nor4277]

That a great tip about a tube showing good get may not be strong enough in all uses.I bought a little oscilloscope a dso 188 model,I bought the little one hope it might be of some use for me working on tube radios,maybe alignments ,I would love your input of what it might be good for or if anyone else has any input ?

[@RestoreOldRadios]

Thanks Ron. Your scope could be used to look at audio waveforms and RF up to 1 MHz. Testing the I.F. resonant frequency can be done with your scope as well just to name a few. Keep in mind, an isolation transformer needs to be used on the receiver under test if your unit is AC powered. Best, Don

[@James_Bowie]

Excellent video, thanks 👍 (but not a fan of the bouncing circles on the schematic). At 26:22 I don't follow this. How can resistance affect capacitance? What is the reference to John Rider that you cited at 26:07? -- I cannot pickup exactly what you are saying there.

[@RestoreOldRadios]

James, thanks for your feedback on the bouncing circles. In regards to adding a 1 megohm resistor; doing so reduces the capacitance from the meter leads so loading of the circuit under test is reduced. Check out John Riders book on How to Use Meters section 9-11 at: www.americanradiohistory.com/Archive-Rider/BOOKS/How-to-Use-Meters-Rider-1954.pdf Hope this helps and thanks again for watching. Best, Don

[@James_Bowie]

@@RestoreOldRadios Thanks for the (large) document. I understand his point in section 9-11 about reducing the effect of _resistance_ but my question is about capacitance. I cannot see how adding a 1 meg resistor in your case changes capacitance from 58pF to 1.6pF. Where is that explained? Afterthought: What is the shunt capacitance of that resistor? If it is less than 1pF then that in series with 58pF will result in a very low capacitance.

[@RestoreOldRadios]

Starting with section 18 of this document: books.google.com/books?id=gO5HAQAAIAAJ&pg=PA23&lpg=PA23&dq=how+does+a+dc+probe+with+1+megohm+resistor+reduce+capacitance&source=bl&ots=DGfu3obu_3&sig=ACfU3U1jbBQZt1Ya9qWepv5Ob0zOrz0nGw&hl=en&sa=X&ved=2ahUKEwjFob2Zn9fpAhUwgXIEHe0qBMwQ6AEwAHoECAgQAQ#v=onepage&q=how%20does%20a%20dc%20probe%20with%201%20megohm%20resistor%20reduce%20capacitance&f=false

[@James_Bowie]

@@RestoreOldRadios Thanks, that's a good reference (as military training material usually is) and makes clear that's it's capacitive _reactance_ of the input circuit which is being affected by the 1 meg series resistor.