Power Supplies Part 2: Full Wave Rectification

In this Part 2 of the Power Supply video series, I present a brief review of Part 1 and then explain the theory of Full Wave Rectification. In the second half of the video, an oscilloscope is used to present a step-by-step visual overview of the entire rectification process, including the smoothing of ripple with an electrolytic capacitor. I apologize for the camera's difficulty in focusing on the scope CRT, but hopefully it will not detract from the informative content of the presentation.
Link to the video explaining how the filtered DC output can be much higher than the RMS rating of the power transformer: kzbin.info/www/bejne/g4nKeGBmgq51faM
Thanks for watching. Be sure to stay tuned for Part 3, which will be on Full Wave Bridge Rectification.

[@michaelogden5958]

If Uncle Doug had been available in the 70's, I'd probably be a "rocket surgeon" by now! Even so, plenty of tricks being learned here by this old dog. Thanks, Uncle Doug!

[@UncleDoug]

You're welcome, Michael :)

[@JustSomeGuy1967]

A cup of coffee early on Sunday morning and a great Uncle Doug video can't be beat!

[@UncleDoug]

+Mark Jordan Thanks, Mark. I'm enjoying a cup as we speak :)

[@miguelortega7112]

Thank you Uncle Doug. I am buying an oscilloscope as soon as I can. You are the best teacher of electronics, not just valve Amps.

[@UncleDoug]

You're welcome, Miguel. Best of luck with your scope.

[@haroldhayesiii5846]

One thumb up can't really express my appreciation for this clear, concise and informative demonstration. Your willingness and ability to share your knowledge throughout your channel is everything that is great about youtube. THANK YOU!

[@medberdai1253]

I second that. Great video. Thank you

[@UncleDoug]

+Harold Hayes III You're welcome, Harold and Mohammed. Nice comments like yours definitely make it all worthwhile :)

[@decsnspace]

Can't reiterate enough how thoroughly enjoying it is to see all of this in action Uncle Doug. Your RMS and Peak voltage explanation all of a sudden makes complete sense to me. Can't wait to watch your Bridge rectification class and demonstration!

[@UncleDoug]

+decsnspace Thanks, DS. Rusty and I are glad the videos are helpful. Stay tuned for Part 3 :)

[@budandbean1]

You are absolutely the best Uncle Doug!

[@UncleDoug]

+Buddy Martin Thanks so much, Buddy. Nice comments like this make it all worthwhile :)

[@lowheadroom]

I am Sooooo thankful for these educational videos. I would be nowhere without them. You’ve literally made tube amplifiers accessible to a simple guy like me. THANK YOU

[@UncleDoug]

You're welcome, LHR. Glad you enjoyed them.

[@DavidImrie]

Thanks uncle doug! Your videos are prety much single-handedly teaching me how to build amplifiers. Where would the world be without retired guys in sheds!....and rusty.

[@UncleDoug]

Amen, David, just look at the Unabomber :):) Seriously, you're welcome. I'm glad the videos are helpful :)

[@robota.2433]

If you can't explain something simply, you don't understand it well enough. I'm glad I finally found someone who understands this stuff well enough :)

[@UncleDoug]

Good point, RA......thanks :)

[@davidlegault9745]

Thank you - reading it is one thing, but being able to visualize it is really the best way to learn. Regards, Dave

[@UncleDoug]

+David Legault I agree, Dave. If I can see it.....I can generally comprehend and remember it.

[@ethompson526]

Doug you are the single best thing about you tube hands down! Thanks for the years of great videos.

[@UncleDoug]

+Eric Thompson You're welcome, Eric. Thanks so much :)

[@DennisMurphey]

I am now building a lab test power supply to test and operate test projects. My coach or mentor uses terms that are new to me. So i come to you and research your library of tutorial videos and found this series that fits perfectly into the gap i have in EE stuff. Thank You Doug so very much for the time you put into explaining stuff. the finger puppet will be a lasting memory. Great stuff. Dennis in Virginia

[@UncleDoug]

That's great news, Dennis. I'm glad the videos are helpful.

[@johnsmith-hk3pd]

i know i am about 4 years late but i wanted to thank you for these great videos you are by far the best at giving instructions here on you tube, i have an old red bear amp that turns on but has no audible output, not sure if i will be able to fix it but feel more up to the job thanks to you, also i love it that you include your 4 legged assistants in your videos, it's hard to find quality help these days

[@UncleDoug]

You're very welcome, John. Best of luck with your project.

[@STARanoff]

Can't stop watching your videos! Please keep on doing that! Uncle Doug, you are the best! Thank you for your share!!!!

[@UncleDoug]

You're welcome, Сергей. Thanks for watching :)

[@BoHunter2010]

Thank you! Seriously this is the most helpful explanation I have ever seen to show how each of the components work independently and how they interact together to give the desired output. Simply fabulous.

[@UncleDoug]

Glad it was helpful, Bo. You are quite welcome :)

[@ronniepirtlejr2606]

These are the best, I've ever seen explained, hands down! Or should I say? Thumbs up! Thank you.... Uncle Doug! :-)

[@UncleDoug]

You are very welcome, Ronnie :)

[@rlsimpso]

This is an excellent explanation of how the supply is smoothed.

[@UncleDoug]

I'm glad to hear that, Robert. Thanks :)

[@raymondbailey7045]

Uncle Doug you are the best, keep up the great and easy to understand videos. Thank god for Uncle Doug !

[@UncleDoug]

+Raymond Bailey Thanks, Raymond......we will :)

[@BjornBlomstrand]

Thank you for the lesson. For me it explains that I always get a hum in my radios. I am a beginner and taking upp the hobby from I where a juvenil. Working now with a Luxor radio from 1950. Will follow you on youtube. Regards Bjorn

[@UncleDoug]

You're quite welcome, Bjorn. We hope our videos are helpful.

[@evanrenberg2682]

Thank you Uncle Doug, I really appreciate all your videos and clear explanations. You're the best teacher I've had. Rusty and Jack are doing a great job helping too!

[@UncleDoug]

You're welcome, Evan, and thanks for your very nice comments :)

[@geoffsearle2778]

Thank you, Doug. Surely, you were a teacher at some stage...you are VERY good at it!

[@UncleDoug]

Yes, I was a math and science teacher in middle school for many years. Thanks :)

[@jangrinaert]

Amazing videos! Since my retirement I've been dabbling in valve amplification, building kits and even doing from scratch builds, but always without really understanding the workings of the circuits I'm painstakingly copying. Since I discovered Uncle Doug's work my knowledge of the basics has progressed immensely. A big thank you! Jan from Belgium

[@UncleDoug]

You're welcome, Jan. It's great to hear that our videos helped you to gain a greater understanding of amplifier circuits.

[@TheBnjmnlrd]

I just understood more about electronics in the last 2 videos than in all of my other efforts of learning.

[@UncleDoug]

That's great to hear, Ben......glad the videos are helpful. Thanks for watching.

[@TheBnjmnlrd]

With Me, you Jack and Rusty and my new skill set I may just get to build my own cloned Fender 5f1 amd more.

[@UncleDoug]

By all means, give it a try. Personal experimentation is by far the best way to learn......just be very careful :)

[@johnruscigno5738]

You make it so much easier to understand with the diagram, thank you.

[@UncleDoug]

You're welcome, John.

[@michaelogden5958]

I have a '73 Bassman 50 that I rehab'd a while back with your help. Although the "Normal" channel works and sounds really great, I must have goofed on the "Bass" circuit. I've been putting off the "Bass" repair since the "Normal" does exceeds my expectations. Anyhow, before going back in, I am reviewing your videos to brush up on the fundamentals. I am amazed anew at how well you explain things.

[@UncleDoug]

Good luck with the repairs, Michael. I hope the videos are helpful.

[@beatleswen]

非常感謝您的教育影片, 我沒有電力學基礎, 但是也能聽得懂你說的, 太感謝您了. 我覺得你是天才教師.

[@UncleDoug]

你的話是最友善和最值得讚賞的。 我們很高興您喜歡我們的影片和教學方法。

[@fullwaverecked]

I finally understand the center tap. Just when I was going to give it the finger, you did the two finger trick and all was clear. Thanks UD! (not sure if teeth and zipper should be used in the same sentence, but I'm thick skinned, so I guess it's ok)

[@UncleDoug]

Glad it helped, FW. Sorry if the images were disturbing :)

[@5barkerstreet]

Thanks for doing these videos . I've watch gust about all of them and I've learn a lot but think I need to go back watch some of them again a refresher tanks

[@UncleDoug]

+paul c You're welcome, Paul. I hope the review is beneficial :)

[@wgiles51]

I remember my Physics and Electrical Engineering professors trying to explain why we used RMS voltage. The explanation that I remember best is that we had to square the waveform because the integral of an alternating current waveform is zero because it goes both above and below zero. The squared waveform is always positive, so we integrate that and take the square root of the result to find the voltage. All of this ignored the real explanation, that the RMS voltage produces the same amount of heat across a resistance as the same DC voltage. Knowing that would have made understanding RMS voltage a lot easier.

[@UncleDoug]

Good comments, Bill. It's also why deviations from the mean are squared in statistics.....to eliminate their sign.

[@bdemski]

Hi Uncle Doug! Thank you for such a clear explanation and real-world demonstration of each step along the way. You really have a knack for breaking things down and making them easy to understand. Hi to Rusty and Jack, too!

[@UncleDoug]

+Brian Demski You're welcome, Brian, and thanks for your nice comments. Rusty and Jack wave back :)

[@tonypotter1937]

Excellent series Doug. It's all coming back to me now!

[@UncleDoug]

+Tony Potter Thanks, Tony. Sometimes a little refresher is just what the (amp) doctor ordered :)

[@SiliconSet]

Great video Doug, many thanks! Jack and Rusty are a riot!

[@UncleDoug]

You're welcome, SS....glad you liked it.

[@arielomc]

Uncle Doug, you are a genius!, with you learn for tube amps it's super easy. Thank you so much! PS: Rest in peace dear rusty :'(

[@UncleDoug]

You're welcome, Ariel, and thanks for your nice words for Rusty.

[@aghast2495]

Thanks for taking the time to make such a clear and concise explanation of the AC/DC rectified waveform. Your power supply videos are great so far, looking forward to watching more on your channel.

[@UncleDoug]

You're welcome, Ag. We hope you enjoy all our videos :)

[@MrMac5150]

I must say you do have a way, of teaching a class.

[@UncleDoug]

+MrMac5150 Thanks, Mr. Mac :)

[@johncunningham5435]

A great refresher; I use to design a lot of linear power supplies with full wave rectification for all kinds of applications, much more efficient to.

[@UncleDoug]

+John Cunningham Thanks, John :)

[@NickBoere87]

Thanks Doug for all your video's. You're the best electronics teacher I have seen. I have leaned a lot by watching your video's. I just finished my first (fender 5F1) amp, and now I'm working on the next amp. A Marshall 1974x. Thanks again and keep up the good work! Greetings from the Netherlands.

[@UncleDoug]

+Nick Boere You're welcome, Nick. It's great to hear from you. Best of luck with your amp projects :)

[@handwoundpickups6555]

This was again fantastic especially when you displayed it on the oscilloscope. 👍

[@UncleDoug]

I'm glad yo enjoyed it, HWP.

[@dembydish]

Excellent explanation and very useful to see it on the oscilloscope. Thank you.

[@UncleDoug]

You're welcome....glad you liked it :)

[@abcdefgh-sh6wr]

All of your videos are certainly informative. Although I am an engineer, I really cannot explain, and elucidate in such a beautiful manner. Thanks for your time and efforts. Please upload some videos about transistors and modern electronics as well.

[@UncleDoug]

Thanks so much, Nasir. I specialize in vintage tube amps, so the modern gear is really not in my area of expertise.

[@TheRandomDave]

this video was simply amazing. thank you so much for your work, Uncle Doug.

[@UncleDoug]

Thanks, Dave. Glad you enjoyed it :)

[@audiotechlabs4650]

This latest series is one of your best! You do seem to evolve, so as your loyal followers learn and evolve, so do you. Just goes to show if you use your brain you never stop learning and improving. I wonder how you will come up with new and exciting topics which still relate to our love of tube amps, and Bam! Here we go again. Thank you again for sharing! Thankz

[@UncleDoug]

+Audio Tech Labs You're welcome, ATL. I learn a lot while preparing these videos and hopefully will be able to steadily ratchet up the level of complexity as my own understanding increases. I try to stick with topics that really interest me, and therefore am able to impart some enthusiasm for the subject that will be contagious to the viewers. Thanks for watching and for your very nice comments.

[@damianvila]

Perfect, Uncle Doug! Your explanation is flawless and entertaining. Thanks!

[@UncleDoug]

+Damián Vila You're welcome, Damian. Thanks for watching and commenting :)

[@tobortine]

That was the best explanation of this subject I've ever seen, thank you.

[@UncleDoug]

+tobortine You're welcome, T, and thanks for the very nice compliment :)

[@ernestschultz5065]

You must have been a wonderful teacher. I actually know now what rectification is but I'm not sure you could have got me to understand algebra.

[@UncleDoug]

Thanks, Ernest. I'll bet I could ;)

[@r.charbon2028]

I just watched this for the 3rd time. Your are the best Uncle Doug, really this is the best video on the topic. Thanks again (...I wish you would start making other such videos again). Regards, rc

[@UncleDoug]

You're welcome, RC. Thanks for your very nice comments :)

[@vhm14u2c]

Beautiful demonstration with scope , PS, diodes, and caps :-)

[@UncleDoug]

Thanks, Vince.

[@MauroSedrani]

I very appreciate the way you teach. Great job. Greetings from Italy!

[@UncleDoug]

+Mauro Sedrani Thanks, Mauro. It's good to hear from you :)

[@worldwide1376]

Super helpful, outstanding teaching skills. Thank you.

[@UncleDoug]

That's great to hear, WW :)

[@Echo_III]

One of the most informative, non-idiotic channel on KZbin. I love to watch your videos sir. Cup of coffee, few schematics of my lovely amps and pen in other hand to add new info on paper. I have one question about that video. What's the most diffrence between tube rectification and diode rectification? Any significant diffrence in sound, hum etc?

[@UncleDoug]

+echo Thanks so much, Echo. Rusty and I really appreciate your nice comments. Diodes tend to be more efficient than tubes when it comes to rectification.....other than the GZ34, which is very close in efficiency......so tube rectification can impart an effect called "sag", which is evident when the power supply lags behind the demand for more current (generally at higher volumes and stronger input). Some people love this effect, since it is associated with vintage tone......some people dislike it and prefer diode rectification.

[@Echo_III]

I am reviewing all of your videos right now :) Nice to watch. I now know much more then year ago. I was going to put a comment and... hah, I've done that year ago.

[@Billo1281]

Your videos are always a pleasure to watch. Thanks for passing on the knowledge, kind sir.

[@UncleDoug]

+Billo1281 You're welcome, Bill :)

[@cassvirgillo3395]

Hi Uncle Doug & Rusty, lets not forget Jack, Most excellent demonstration and analogies used in the video, you really make it easy to understand the information being delivered. I'll bet your class at school was a favorite of the students. Sorry if you thought I missed the point of the 1/2 wave rectification process, just curios. I'm sure Fender knew what they were doing, and, as stated, to supply the grid of the output tubes, which you said are not as discerning as the preamp tube, 47uF filter cap is adequate. You could make a series of instructional DVD's, the amp builders companion. Your the best on YT for learning about amplification. I'd bark for that big cookie too. Thankyou for the lesson. I can't wait for the rest of the series. Take care, C.

[@UncleDoug]

+Cass Virgillo You're welcome, Cass, and thanks for your continued interest and support. Rusty and I (and Jack) really appreciate your nice comments.

[@audiotechlabs4650]

I totally agree! Uncle Doug is far above the rest. His method is flawless, and he will respond to questions. Anybody can learn and benefit from these wonderful videos. We are so lucky to have Uncle Doug and Rusty and Jack! Thankz

[@UncleDoug]

Wow....a big "thank you" and "you're welcome" from Rusty, Jack, and old Uncle D :)

[@mixolydian2010]

Thanks a lot Doug brilliant series, all the best Colin.

[@UncleDoug]

+mixolydian2010 Thanks so much, Colin :)

[@mosestewelde8163]

Hi Doug, I can't find part one of this video. I just discovered your channel and I'm loving it. Keep up the great work!

[@UncleDoug]

Here is Part 1, Mussie: kzbin.info/www/bejne/e4XUe3dvpttrsMk There are four videos in the series.

[@mosestewelde8163]

I don't even know what to say. You make my college classes a piece of cake.

[@redfishbum]

Great videos. Thanks for the series. Really like the scope stuff!

[@UncleDoug]

+redfishbum You're welcome, Bart. I wish the camera liked the scope as much as we do.....but I think/hope the images are clear enough for our purposes :)

[@yrulooknatme]

thank you. Good finger painting skills & finger puppet technique! Center taping that 2ndary coil changes things quite a bit! I've always wanted to understand how amplifiers worked. I'm lookin forward to your next video on this.

[@UncleDoug]

+yrulooknatme You're welcome, YRU. As we will see in the next installment, adding two more diodes makes the center-tap unnecessary......so stay tuned :)

[@c.p.1589]

These videos are tremendous Thanks. I think Rusty may have reached 'peak' cookie.

[@UncleDoug]

You're welcome, CP. Rusty's capacity for cookies exceeds all rational expectations.

[@SandersAmps]

Thanks Uncle Doug! Always good! Great teacher.

[@UncleDoug]

You're welcome, Shaun.

[@edwardhannigan6324]

Hey Doug, Wow what an explanation and demonstration..Love it..! My mind is clear now about rectification etc..Thanks ..Ed..U.K..😀

[@UncleDoug]

That's good news, Ed. Glad to hear it :)

[@pinkponyofprey1965]

My guess is that this will be an amazing eye opener series! :D

[@UncleDoug]

+PinkPonyOfPrey I sure hope so, PPoP. Rusty and I will do our best to meet your expectations :)

[@pinkponyofprey1965]

Maybe you should call him Resty ... :D

[@UncleDoug]

Either that or Fidon't :)

[@DeadKoby]

Electronics explained for rookies.......explained by Uncle Doug. Are we gonna do Full Bridge next?? I do know this stuff, but I like the refresher, and I need to teach this to others, so learning how to explain it so that a novice can "Get It" is important. Thank you Doug for providing a channel where we can all learn to improve our understanding of electricity and electronics. Your channel is a great place for the novice to learn. Note that I use words like novice, or rookie.... Anyone who works to get smarter is not a dummy, and idiot or "average"... and I scoff at book series that calls them that.

[@UncleDoug]

+DeadKoby Yes, indeed, DK.....in fact, I am uploading Part 3 on FWBR as we speak. You're welcome. Rusty and I really enjoy interacting with viewers all over the world, and hearing about their progress and appreciation definitely makes it all worthwhile.

[@mickduprez9598]

Great video Uncle Doug, it's good to see the theory clearly explained as well as a practical demonstration, very helpful. Rusty looks like he might have a bit of Australian Blue Cattle dog in him yes? Thank you for all your efforts and keep up the great work!

[@UncleDoug]

You're welcome, Mick. Rusty, who is indeed a Queensland Blue Heeler, and I are glad our videos are helpful :)

[@fullwaverecked]

920 vac peak... No wonder we keep one hand in our pocket. Very informative. Thanks!

[@UncleDoug]

Glad it was helpful :)

[@davearnold4426]

your hand acting is superb!! :)

[@UncleDoug]

Thank you, Dave. My many hours of study have really paid off :)

[@curtisprice9806]

EXCELLENT! 👍😀 THANK YOU UNCLE DOUG!

[@UncleDoug]

You're welcome, Curtis :)

[@jjheaphy]

Great use of the scope!

[@UncleDoug]

Thanks, John :)

[@JoaoMartinsguitar]

We are happy you are back. This power supply explanation has been awesome!! I´ve been working on my fear of transformers and I believe in the next month I will be receiving the components to by build my very first tube amp. Which one would you suggest for my first project?? The 5e3 or Epiphone valve junior? Best Regards uncle extended to Jack and Rusty.

[@UncleDoug]

+Joao Martins Thanks, Joao. As a Fender enthusiast, I would strongly recommend the 5E3. It's one of the classic amps of all time. Good luck with your project.

[@GRobLewis]

Hey, Uncle Doug. Your videos have been a great refresher for a guy who went through EE school early in the solid state era. I learned more about tubes as a teenager reading books than I did in college. Question: I seem to remember that early in the hi-fi audio era, some companies tried to cut hum to an absolute minimum by running the heaters of their tubes on DC current rather than the usual AC. Are you aware of any guitar amp manufacturers who did the same thing? Might this be an interesting mod for people looking for the last ounce of performance?

[@UncleDoug]

It is done in some amps, Rob, but the truth is that if a circuit is properly designed and constructed, rectification of the filament supply is simply not necessary.

[@AndyWragg]

Great video Doug I'm running out of colourful adjectives to describe your talent here. My only gripe/observation would be to explain why/how you got the 2 output waves to appear seperate on the scope. I guess that comes down to how to operate a scope which is 'out of scope' of this lesson.

[@sootikins]

+Andy Wragg Well, the short answer is that he's using a 2 channel scope. Each channel has an input and a trace. Signal on "A" input is displayed as the "A" trace (IOW the trace that's manipulated by the controls in the "A" section of the front panel) and then likewise for B. By setting up the A and B range and position controls properly you can put each trace in its own part of the screen (see 15:10) or lay them on top of each other (see 15:30) or just show one trace filling the whole screen (see 12:45) or whatever else you want to do.

[@UncleDoug]

+Sootikins Excellent answer, Sooti. Thanks for helping out :) A dual-trace scope is very helpful with amplifier circuits, particularly when examining phase inverters and PP output. I have been asked several times to do an oscilloscope video and intend to do so in the future.

[@AndyWragg]

+Uncle Doug. As you know ( from yesterday's comments) I myself already have a dual channel scope and know how to offset the dual traces. My point was that not everyone has this tool or may know how to use it to its full potential as you have here. Again not a criticism more an observation.

[@UncleDoug]

Understood, Andy, and I will definitely place an oscilloscope video at the top of the to-do list.

[@homestarMUHFIN]

Interesting stuff, can't understand most of it cause I don't have much background knowledge on power. But I aim to change that soon, keep it up!

[@UncleDoug]

+Jeremiah Joseph Ox Thanks, JJ....we will :)

[@SNORKYMEDIA]

hahahha I burst out laughing when the "polarity fingers" came into shot....Brilliant as usual

[@UncleDoug]

+SNORKYMEDIA Thanks, Snork. I spent a lot of time and money on hand-acting lessons, and it really paid off in this video :)

[@SNORKYMEDIA]

Marshall Ward will be ringing soon for their next catalogue shoot

[@UncleDoug]

I'm only into hand-acting as an artistic outlet, Snork. I would never prostitute my phalanges for monetary gain :)

[@iamsuengas]

thank you for your clear and precise explanation of how AC to DC power rectification works, your explanation is very helpful I do appreciate that, I'm having difficulty trying to choose and purchase a bridge rectifier for my 70VAC power supply I don't know which one to use, I need 50DC, can you help me on this...thanks.

[@UncleDoug]

You're welcome, Iam :) We used to get our FWBR's from Radio Shack, but I guess that's no longer an option. I would check on Ebay for a FWBR that can handle whatever current demand you anticipate. Good luck :)

[@tremelo68]

This is really instructive. Love it. Feel like I am really getting an education here. Can you explain how you choose the filter uF. I understand the voltage needed but why 22, 33, 45, 80, 100 uF for filter caps in various amps.

[@UncleDoug]

That's great to hear, Trem68. We're glad the videos are helpful. The capacitance required for smoothing of the rectified B+ is dependent upon several factors, including the type of rectifier used, and the value of the internodal capacitors. Most people simply use the values stated on a schematic of the circuit being built or a very similar one, but if you have an oscilloscope, you can actually use trial and error to get maximum smoothing with minimum capacitance.

[@kloner]

Another good video. Thanks. Does anyone give you grief about the 'vintage amp repair guy' that named his pets Rusty and Jack? I guess it's better than Oxidized and Input. ;-)

[@UncleDoug]

+kloner Thanks, K. Actually, I never thought about the irony of those names, until you mentioned it......the connection (so to speak) was purely coincidental :)

[@budandbean1]

+Uncle Doug Ha ha ha... Rusty, Jack, Now that's funny!

[@satchboogie2058]

+kloner I never noticed :P

[@wtangodelta1715]

Huh! I never made the connection...

[@DoomRoomRecords]

Great to see the truth on the oscilloscope

[@UncleDoug]

Glad you enjoyed it, DDR.

[@ulisesaguilar4392]

great video Doug

[@UncleDoug]

Thanks, Ulises :)

[@FrankGatta]

Best video yet : )

[@UncleDoug]

+Frank Gatta Wow....thanks, Frank :)

[@wrenchhead944]

Great job of explaining

[@UncleDoug]

Thanks, Brian :)

[@wegert1]

I really enjoy all of your vids. I got an associates degree in electronics technology many MANY years ago before moving on to computer science and a career as an engineer; I didn't think this field even existed any more. So I'm really enjoying re-learning this stuff and look forward to building a nice little amp (I'm a guitar player...) and being able to tweak the sound based on solid fundamentals. Anyway, it really threw me that in your lead-up on theory the transformer was multiplying the voltage out, and then when you did your experiment the transformer was reducing the voltage....with no explanation. Did I miss something? Please explain, I NEED to be on the same page before moving on. Also, I would love to buy a scope, maybe an old Fluke or Techtroniks like yours. Maybe you could to a vid on using the scope and other equipment as a refresher for us old farts. Thanks again for EVERYTHING! If I don't electrocute myself I'll let you know how my amp turns out...

[@UncleDoug]

You're welcome, RSF. It all depends on which way the transformer is oriented. If you have a 120:12VAC, it will reduce the voltage, but if you reverse it, i.e. 12:120VAC then it will increase the voltage. It's the same transformer, just rotated 180 degrees. The 120:400VACpower transformer for an amp will increase the voltage by 1 to 3.3, but when using the scope, I use a 120:12VAC output transformer for low voltage.

[@wegert1]

Got it. Thanks again

[@UncleDoug]

You're welcome

[@drguitar2585]

i like your videos and your dog!!

[@rhoneranger549]

This is awesome Uncle Doug! I am so glad that Rusty is finally doing something :) SO, with the larger bias voltage (say 325 like in the first video) could the same be achieved with only 2 20mf-400 volt capacitors? In this video, it took only 2.

[@UncleDoug]

+Rhone Ranger Thanks, RR.....So am I :) In a functioning amp circuit, quite a bit of current is flowing. The more current, the tougher it is for the filter caps to smooth the DC output, so generally you need at least 3 filter caps to ensure smooth DC, particularly for your pre-amp tubes (the most sensitive of the tubes).

[@rudiyang7790]

Hi from Jakarta Indonesia, I recently getting interested in electronic and your video helps me a lot, so thank you very much. I have a question though, how do you determine the value of the smooth capacitor? thanks again

[@UncleDoug]

You're welcome, Rudi. Most tube handbooks will give you the value for the first filtering capacitor depending on which rectifier tube you use. The subsequent filter cap values are generally of lower value. Although there are mathematical ways to calculate the values, I tend to look up circuits that are similar to the one I am designing/building and then see what they use.

[@larryb.lindsay2366]

Damn, I wish you had been my instructor when I was taking theory classes

[@UncleDoug]

I wish I had been too, Larry.

[@DaveHilts]

thanks UD for taking on this topic! I am learning so much and appreciate every one of your videos. Rusty is in top form but I worry about Jack, has he developed a catnip issue?

[@UncleDoug]

+Dave Hilts You're welcome, Dave. We have booked a room for Jack at the local substance abuse center and are praying that he can get the "catnip monkey" off his back in time for the next video :)

[@bullthrush]

The Oscar for best make-up in a hand acting electronics video goes to..... :)) Another excellent demonstration of theory matching reality, thank you for the time you take to do this!

[@UncleDoug]

+bullthrush I added that part just for you, Andrew :) It is surprising how well the oscilloscope images match what we're told is going on in those snakey little wires. Generally, expectation and reality are miles apart :)

[@TheBeet21]

Hey Uncle Doug! I really love your videos. You've been a great help. One question though. I'm yet to buy a power transformer online for my heavily modified "Fender Twin-esque" project. I think I'll need more power that's why I probably need to buy a bigger power transformer. My question is, are the voltages specified in the secondary winding of these power transformers in RMS or are they in peak? I have a hunch that they're in RMS but I want to make sure. I have to admit. This is one of those times that you wish you've listened to your electronics professor in college more closely. But what can we do? Good thing you're there to explain everything in a very simple way for dummies like me. Thanks Uncle Doug, and keep up the good work!

[@UncleDoug]

+TheBeet21 You're welcome, TB. In my experience, the secondary outputs are always stated in RMS.

[@TheBeet21]

I see. Thank you very much! Please do not get tired of making more videos. Greetings from the Philippines :)

[@UncleDoug]

You're welcome, TB.

[@ryansequeira7938]

Uncle Doug, how does one compute the amount of "loss" that results from the rectification process? I saw in your scratch built vintage amp pt 3 video, you ballparked about an 80V loss as a result of using a 5Y3 tube, but you didn't mention how or why this happens. How does this differ from using solid state diodes? Is the loss from SS diodes just the forward voltage for the diode type multiplied by the number of diodes in use?

[@UncleDoug]

Diodes are much more efficient than tube rectification, Ryan. My estimates were simply based on experience. Tubes convert quite a bit of energy into heat. With regard to diodes, the loss can be calculated as you suggest.

[@ryansequeira7938]

@@UncleDoug awesome, thanks for taking the time to respond!

[@michaelogden5958]

I have a question. On some (or maybe all?) Fender diode rectifier boards there are three diodes in series for the "top" 330V side of the power transformer and three diodes in series for the "bottom" 330Vside of the power transformer. Why is that? You say that there is some loss across diodes. Are they using multiple diodes to step down the rectified voltage? Thanks!

[@UncleDoug]

I personally think, since diodes are so inexpensive and their function is so critical, that using multiple diodes is a safety measure....."spares" so to speak......if one fails, then there are two more to take its place.

[@GregsGarage]

What's the matter Rusty? Jack got your tongue? Great explanation U.D.!

[@UncleDoug]

+Greg's Garage Thanks, Greg. I hope you watched to the end, where Rusty redeemed himself :)

[@GregsGarage]

Oh yes I did!!! It was like his synchros weren't meshing and he couldn't get it into gear. As usual though, Rusty came through when it mattered most.

[@UncleDoug]

He always does.....hence his richly-deserved nickname "Rusty the Wonder Dog".

[@rtybn2012]

To see the ripple ( 120Hz ) you need to add a load from the junction of the 2 diodes (cathodes ) to the center tap of the transformer. The caps will charge to peak voltage of the rms voltage will no load.

[@UncleDoug]

Thanks for your helpful input, Henry.

[@owennikish7995]

Great video once again 👍

[@UncleDoug]

+Owen Nikish Thanks, Owen :)

[@charlesgwyn2115]

Great job, as usual. Hope you got the + and - off your fingers! :-)

[@UncleDoug]

+charles gwyn Thanks, Charles. I haven't yet, but hope to before going out in public. With the tattoo craze going on lately, I may start a new fad :)

[@stevenwilliamdewitt]

Great video series! Maybe Rusty is dealing with laryngitis? Jack seems to be less than enthusiastic about this topic.

[@UncleDoug]

+Steve Dewitt He's less than enthusiastic about any topic except eating and sleeping, Steve. If you watch to the end, however, he redeems himself :)

[@bradcoley2895]

.....dude you teach!....good!.....

[@UncleDoug]

Thanks, Brad :)

[@EUC_Senior]

Thank you for demonstrating on the scope what everything looks like! Also, I think you have ink on your fingernails? 😀

[@UncleDoug]

You're welcome, Mark. It was probably left over from drawing my charts.

[@cBroadbo]

Fantastic series on power supplies. Question for you. I was looking at a schematic for a Fender Bassman 6G6-B and saw something that I don't understand. That circuit uses solid state full wave rectification with a center tapped secondary on the power transformer. The strange thing I see is that each side that comes from the secondary winding runs through 3 diodes in series. Do you know why they might do that?

[@UncleDoug]

Thanks, Craig. I've heard several explanations, ranging from "Three diodes produce a smoother DC output", to "Diodes are cheap, so throw in a few extras in case one fails". The truth is probably a combination of both.

[@cBroadbo]

Thanks UD! Sounds like I should wire up a bunch of diodes and look at the waveform on my scope to see if it's any smoother.

[@UncleDoug]

I'm not sure if the smoothing will be visibly evident, but regardless, it will be an interesting experiment.

[@bertuspa3grn]

Good Morning Thanks Uncle Dog good video Bertus

[@UncleDoug]

+Bertus pa3grn You're welcome, Bertus :)

[@allanpennington]

I require a B+ of 300V for an amp build. The schematic shows a Tx as 300-0-300 120mA with an EZ81/6CA4 rectifier tube. The initial filtering is two 32uF caps and a 1K resistor connected to pin 3 cathode of the EZ81. The schematic shows a secondary output of 300V at each of the two secondary taps with the CT earthed and a current draw of 20mA. The voltage is 390 at pin 3 and a 300V B+ after the first filter stage. Can these figures be correct? Would the 390V be peak or RMS? I am still a little confused despite watching all the videos. Guess I am having a bad senior moment! I want to buy the right power Tx. I looked at a tube spec and am I reading it correctly that with a 300-0-300 Tx and a current draw of 20mA with a 240 Ohm limiting resistor the voltage output of the rectifier is 390V. That is, as current draw goes up, B+ voltage comes down??? My schematic has a 1K resistor however.

[@UncleDoug]

When the transformer output is tube rectified, it goes down due to rectification losses, then when it is filtered, it is increased because the filter caps smooth it to peak (not RMS) voltage. The end result is that a 300-0-300 PT will produce a B+ of much more than +300VDC. Yes, current and voltage are inversely related, so as one goes up, the other goes down. If you use your thumb to reduce the flow of water (current) in a hose, what happens to the pressure (voltage) in the hose?......and vice versa.

[@rayford21]

To avoid confusion on how U.D. read the scale on the output side of the transformer on his analog meter please note at 9:28 he is reading 1volt a.c. on the lower RED scale of the meter when the range switch is in 2.5v and A.C. is selected on the function switch. At 9:55 he is reading 12.7vac on the BLACK scale 50 row when the range switch is in the 50v and A.C. on the function switch. He switched from the 2.5v scale to the 50v scale before reading the 12.7vac. I'm not a wise guy, just cluing you in, just in case you're not familiar with analog scale-and-needle voltmeters...have a nice day.

[@UncleDoug]

Thanks for your helpful input, Rayford :)

[@hadireg]

❤