Isolation Transformers

[@UncleDoug]

Before posting a comment or question, please see if it is addressed in the video description "Clarifications". Thanks to all of you who helped us reach a major goal of 50,000 subscribers !!

[@leemaples1806]

Congrats on the 50K milestone. I think it just means 500K - 1M folks out there still havnt heard of you before. :-) Cheers Uncle Doug!

[@UncleDoug]

Thanks, Lee. I guess we'll just have to win them all over :)

[@benten6507]

One day I'll thank you by giving a ride on one of those cars.

[@UncleDoug]

Sounds good, Ben.

[@VashthStampeede]

This is a bit after the fact, but here goes. This pertains to your engine. I was a California Air Resources Board certified inspector and installer of smog devices in the early 1970s. This is what I know about engine health. The oil filler tube on your intake manifold was popular on early V8s. It was usually a source of fresh air filtered through a steel mesh filled ventilated oil cap. The harmful crankcase vapors were evacuated through a road-draft tube attatched to the upper rear of the engine. The tube hung down to just below the oil pan where air passing under the engine created negative pressure in the tube. In 1961 the road-draft tube was replaced with a metered valve connected to the intake manifold using manifold vacuum to positively ventilate the crankcase (PCV Valve). Later, the ventilated oil cap was replaced by a solid cap and a hose nipple was added to the oil filler tube so fresh air could be supplied through a hose connected to the filtered side of the air cleaner. Eventually both the PCV Valve and fresh air supply were moved to the left and right valve covers. The point is that you have eliminated the evacuation source on your engine by installing solid valve covers and discarding the device necessary for removing harmful water vapor, blow-by combustion gasses and acids. The PCV Valve was the only add-on smog device of that era that was actually beneficial to an engine.

[@rmdatv]

Despite Uncle Doug’s extensive knowledge of tube amps, it is his uniquely gifted manner in which he is able to communicate it to us mere mortals that is his pure genius. If our American PS systems had more teachers like this, we’d be in great hands.

[@UncleDoug]

Wow....thanks so much :)

[@captainfineweather5610]

Nothing like an evening with Uncle Doug TV! I bought a Hameg 312-5, a relatively simple, single channel oscilloscope and a Heathkit IG-72E signal generator (I love vintage gear) and now I'm confidently attending your class. Thanks man.

[@UncleDoug]

I hope it's helpful, Capt.

[@captainfineweather5610]

@@UncleDoug It very well is! The Heathkit hasn't arrived yet; needless to say that it will require a thourough inspection...! I believe a 230V > 230V 500W isolation transformer will be sufficient to plug my VOX ACs and the little pseudo-Champ in? And the Heathkit, too? The mains fuse of the AC15C1 (which is rated at 100W input power) for instance reads 250V 680mA, so doing the math I come up with 170W peak, if it ever occurs at all.. Or did I take a wrong turn somewhere?

[@UncleDoug]

@@captainfineweather5610 All those numbers make me dizzy, Capt. Just try it and see. Good luck.

[@captainfineweather5610]

@@UncleDoug Right you are. I should rather be more self-confident that making Uncle Doug, of all people, dizzy with numbers I might as well keep to myself. Quite disrespectful. I apologize for that.

[@UncleDoug]

@@captainfineweather5610 Apology accepted, Capt. How did the experiment turn out ?

[@tronics666]

Uncle Doug - Here is why I think your tutorial are so well taught. You have the right pacing and subject focus, humor, rich content, appropriate amount of repetition, interesting illustrations, a way of generating interest in the subject and of course the bonus features. You teach like a pro, not just some KZbin guy.

[@UncleDoug]

Wow, thanks so much for your very kind and favorable analysis, T6. I sincerely try to accomplish the goals you mention, and will continue to do so as long as nice viewers like you can benefit from it.

[@jeremiahchamberlin4499]

I love seeing Jack again, due to the persistence of video images, or at least I saw his outline under the blanket. 🙂

[@UncleDoug]

Jack appreciates your interest and support, Jeremiah. Thanks for your input.

[@Evergreen64]

Thanks! I'm glad you started at the pole. I always knew that your house got 2 phases of AC. But I never understood why the neutral and ground were bonded. Now it makes perfect sense!

[@UncleDoug]

Glad it was helpful, E.

[@sting1111]

It’s winter again so I am back in the classroom. I have watched several videos about isolation transformers. I always had the one nagging question: Why is it ok to ground the scope to the chassis if the device under test is connected to the iso transformer and it is grounded to earth? It finally hit me after watching 2 or 3 times…the horses don’t want to cross over to the mains even though the chassis is technically grounded to earth. Your analogy explains it perfect. You can’t totally eliminate risk but there is a way to work on these amps safely if you always use the cautions diligently. Thank you again Uncle!

[@UncleDoug]

You're welcome, Sting. Stay healthy :)

[@boonedockjourneyman7979]

This is the most important topic in your field. It is followed closely by proper power up, cap discharge, etc., etc. You provided an excellent description that your community can only benefit from.

[@UncleDoug]

Thanks so much, BJ.

[@morik3188]

I have watched 4 or 5 videos on isolation transformers in the past week. Got the basics of it, but didn't fully click. Uncle Doug, you made it click. I'm sure you hear this all the time, but you really are a wonderful teacher. Thank you for taking the time to help out the newcomers like myself to the hobby.

[@UncleDoug]

You're welcome, Morik. I'm glad it was clear and helpful.

[@georgekrabs6948]

Well done uncle Doug safety is of utmost importance and particular channels don't emphasize this and probe around the inside of amps with rings on their fingers and scoff if you leave remarks about their negligence

[@UncleDoug]

Thanks, George. Cemeteries are full of people who got too careless :)

[@345builderman345]

Wow, I can't believe it. I was reading an article on isolation transformers, trying to get an understanding of them & a little box popped up at the bottom of my screen saying you had just uploaded this & now I understand. Thanks Uncle Doug

[@UncleDoug]

You're welcome, Jack. A coincidence??? I think not :)

[@Valerifon1]

With just a couple of your videos, I have gained such a clear understanding of isolation transformers and the benefits they provide in protecting us and our scopes! You're an excellent teacher and your videos are just outstanding! I can hardly wait to see the rest of your videos! I'm downloading these to put in my library! Thanks for the clip on the car show! All the best - Luther

[@UncleDoug]

You're welcome, Luther. I'm glad to hear that the videos are helpful :)

[@muddysledge]

This is one of the best explanations of ground isolation and how electricity always returns to it's origin. Your a great teacher and thank you for sharing your knowledge.

[@UncleDoug]

You're welcome, MS. Glad you found the video to be informative.

[@CovertCulvert]

Again, Uncle Doug, you have taken what can be a confusing subject and made it easily understandable to us lowly newbies. Great analogy! Thank you for a thorough and clear breakdown of the need for using an isolation transformer.

[@UncleDoug]

You're welcome, M47. Thanks for your nice comments.

[@priceamp]

Thanks teach (“I don’t feel tardy”), I mean Uncle Doug for another educational and entertaining video. You have a unique way of bringing the forest into vision where I seem to many times only see the trees. Your teaching style reminds me of my favorite EE professor. He had such a seductive way of teaching we all looked forward to every one of his classes. Everybody always just wanted to hang out with him after class. He authored his own book, which is one book I will always keep. PS: you’ve upped my passion with hotrods too BTW. Your commentary at the car show cracks me up. Jeez, guitars, amps, motorcycles and cars. Life is great, eh?

[@UncleDoug]

You're welcome, Jack. Thanks so much for your very nice comments. Yes, life is good, especially if you refuse to act your age and continue doing all the things you love.

[@curtisroberts9137]

Excellent video and commentary on how this works. The examples of horses are so good to help visualize! I think it really helps us realize how important an isolation transformer really is.

[@UncleDoug]

Thanks, Curtis.

[@matts7975]

Uncle Doug just answered questions that no one has been able to answer me in years

[@UncleDoug]

We're glad the videos are helpful, Matt.

[@brentstewart59]

This is tremendously helpful Uncle Doug. I've been zapped more times than I'd like to admit with old widowmaker amps and now I know why. Thanks for this

[@UncleDoug]

You're welcome, Brent. I'm glad it was helpful.

[@steelcity321pb6]

Isolation transformer use and theory is a very useful subject Douglas. At the age of sixteen, as I began my five year apprenticeship for audio, and television servicing, isolation transformer use and theory was covered in similar detail. It is an essential part of health and safety for every radio, television, and audio (and white goods) restoration enthusiast. Though I’m au fait with the use and theory of isolation transformers, I’ll nonetheless say, “Thank you.” Regards Phil.

[@UncleDoug]

You're quite welcome, Phil. Thanks so much :)

[@captainfineweather5610]

Hi Uncle! Still no Isotrans in sight, at least none that would fit in my purse. But, comes a time! I'll report back.

[@Mortankhamun]

I built a Vox AC4 after learning how amps work from your other videos. I have it working and it sounds great, but the tremolo isn't working, so now I'm watching your isolation transformers and oscilloscope videos to troubleshoot that issue. Thanks for the great videos and information! I've really learned a lot.

[@UncleDoug]

I spent the morning troubleshooting a Princeton Reverb tremolo, Mort. Try different oscillation tubes......some work better than others.....and be sure your three loop caps are of correct value. Good luck.

[@Mortankhamun]

@@UncleDoug Thanks! I tried both the original loop cap values and some modified values I found on a message board and neither really worked, but I haven't tried a new tube. Thanks for the suggestion! I hope you got your Princeton figured out!

[@godfreydesilva5222]

Excellent video. Hats Off dear Sir.

[@UncleDoug]

Thanks so much, Godfrey :)

[@graxjpg]

Just found the channel after watching the guitologist for a couple weeks, killer video. Can't wait to go back and watch all the old stuff.

[@UncleDoug]

Welcome aboard, Grant. Brad and I are old cronies.....so you should feel right at home.

[@tonymanns8249]

Doug, many thanks for your videos that take great care to teach everyone about both the joys and the extreme dangers of electric circuits.

[@UncleDoug]

You're welcome, Tony :)

[@willykanos1044]

Thank you, Uncle Doug. It helped me to understand that I did wire my Airline amp correctly, placing the Isolation transformer ahead of the fuse and the switch. I played my guitar through the Airline this morning. Jim

[@UncleDoug]

You're welcome, Jim.

[@Bigjoedo66]

Another Great video Uncle Doug!! Jack's videography is truly unrivaled

[@UncleDoug]

Thanks so much, Joe. I'll tell him.....if I can find him :)

[@squeezebottle]

I have that exact same Montgomery Ward amplifier, in its original Masonite "TV front" enclosure. I found it in a junk shop around 20 years ago, and the owner said he felt like he was ripping me off by asking $20 for it; he said that his son must have bought it somewhere around 1958-1960 and it just lived in a corner for the 40 years after that. I believe that was one of the Wards amps that was made by Danelectro. The capacitors were completely open with no resistance and no capacitance, the 2-prong cord was completely crumbled and frayed, and the speaker had almost completely dissolved, but it was 100% rust-free somehow and had NOT A SINGLE fleck of white paint on the top; I think the quarter inch of dust on top must have formed a protective shield. With all the "necessary upgrades," a Tung-Sol 6V6 in it, and the original 8" speaker upgraded to a 10" it's got a really nice full, throaty sound and breaks up a little bit at higher volumes.

[@UncleDoug]

It sounds like a neglected amp found a good, appreciative home, Chris. You are both fortunate :)

[@carldavis8228]

You did a fairly good job getting out of explaining 3 phase input to housing single phase voltage. Not a critique but an applause. Great view of understanding earth ground to neutral. Most folks still won't really get it until a short to ground goes through their scope. I say this because it took that for me. Great video.

[@UncleDoug]

Thanks, Carl. I admit that there was some superficiality and minor errors (in the pursuit of clarity) in the AC mains presentation, but hope that overall, it accomplished its mission, which was an explanation of Isolation Transformers. Thanks for recognizing that.....and our efforts in that regard.

[@JamesGMunn]

Very informative! One extra safety note, once you hook the scope ground into the isolated circuit return path, the circuit has lost isolation and current can run through you and the earth back to the "isolated" return path via the scope probe ground if you accidentally touch the isolated source circuit. A simple light bulb demonstration might clarify this issue. This is also true for the secondary winding circuits. Handheld voltmeters are by design isolated from earth ground and are generally pretty safe within their design specs but the grounded oscilloscope probe shield is a significantly different situation than the truly isolated voltmeter that people tend to get used to first. I am sure there are better ways to phrase this but a demonstration is the best instruction tool. Thanks for all your hard work Uncle Doug!

[@UncleDoug]

Thanks for your input, James :) I will keep your suggestions in mind.

[@UOttawaScotty]

hmmm, yeah good point, I never though of this before. So basically, as soon as you hook the scope shield up to the DUT, make extra sure you dont touch anything.

[@donlunn792]

J

[@donlunn792]

James,

[@donlunn792]

James,I know this is a year ago,but my brain is up against the same situation.It does seem that there is no safe way to use an oscilloscope,on,in particular old valve equipment.I have tried on the net to clarify this, but there are so many conflicting opinions.I personally have given up the idea of using an oscilloscope on valve radio gear.Which is a shame as I thought that’s what they were originally used for.Back in the 70s my local radio repair shop had oscilloscopes on the bench.And their work still included valve radios and TVs.

[@jackallen6261]

I knew there was a reason I am not a fan of horses....Love the viewer submission! As always a great and very informative video. Thank you.

[@UncleDoug]

You're welcome, Jack. Horses are dangerous at both ends :)

[@bluesman97]

Thanks for putting me in the Saddle on the Isolation Transformers. Your a Fantastic Mentor.

[@UncleDoug]

Glad you enjoyed the video, BM :)

[@mikemullenix6956]

Thank you sir for this excellent video. You simplified isolation so that even I can understand. This topic is perhaps the most important one for anyone interested in troubleshooting electronics. All of us need a though understanding of this before anything else.

[@UncleDoug]

You're welcome, Mike. You are correct with regard to the importance of this issue, and we wish you the very best.

[@decsnspace]

Another great video and explanation Uncle Doug! This really helped me gain a better understanding in the differences in earth ground and chassis ground. After watching the video it seems to me that this would be a very basic electronics concept to have an understanding of, but I can't recall ever coming across any in depth explanation of it in many of the basic electronics or amplifier repair books that I've read. So thanks again for the video. I also have a Tektronix 2205 that I picked up a while ago on ebay that hasn't gotten much use up until now, so I'm very much looking forward to learning something from your upcoming series.

[@UncleDoug]

Thanks, DS. The problem with most explanations of the issue is that they cause more confusion than enlightenment. I tried hard to avoid that. Since you have an identical scope, you should really be able to follow along quite well. Be sure you have a pair of good probes and possibly an inexpensive audio signal generator.

[@geraldknauss7255]

Just a quick thank you for posting this. Watched the entire thing (except for the car section ;) ) and found out why I have seen references to using an isolation transformer with an oscilloscope, thank you for adding that additional information. By you taking the time to post a video like this, I'm sure you have saved some individuals from having a very bad day. Especially appreciated your thoroughness in showing the power pole ground and tying that into your though explanation of how earth ground is an important concept to grasp.

[@UncleDoug]

Thanks, Gerald. Glad you enjoyed the video.

[@Jnglfvr]

I think that one thing that would be particularly helpful is a realistic diagram tracing current from source from pole transformer secondary to distribution panel to outlet to isolation transformer to DUT and demonstrating lack of a complete current path unless 1) the DUT is grounded 2) the secondary shares a neutral with the "isolation" transformer primary 3) the isolation transformer secondary neutral is tied to secondary (or primary) ground etc.

[@UncleDoug]

Then by all means create such a diagram, BB. We would love to see it.

[@cassvirgillo3395]

Hi Uncle Doug & Jack, Another exceptional tutorial of interest to any electronics enthusiast or Uncle Doug wanna be, I'm one. Thank you for all the time and effort you put into making your most excellent videos. I see your post date of video is my and my Twin Brothers ( he is 6 minutes older ) birthday, June 10, ( 1960 for us ). Wishing you and yours all the best, Cass.

[@UncleDoug]

You're quite welcome, Cass. It's always good to hear from you :)

[@MrSquiggmon]

Another great video, Uncle Doug! One small clarification on the receptacle drawing: The only place your house neutral and ground should be connected is at the service entrance / main panel. Thanks for the video!

[@UncleDoug]

Thanks, Todd. You're right.....but with educational diagrams like these, it's generally best to keep reminding folks about connections and interactions that occurred earlier in the presentation.

[@bixy9347]

Best explanation I’ve seen on KZbin. I love the electron horses analogy, very visual, giddy up!

[@UncleDoug]

Glad you liked it, BB. Off-the-wall analogies tend to stick with us longer :)

[@akdenyer]

Hi Uncle Doug, I bought the chassis stand you recommended. I hate to criticize as you are generally spot on. But you got the earth symbols mixed up. The upside down Christmas tree is like roots in the ground and for an actual ground. The horizontal line with angled downward pointing lines is for a chassis like it was sitting on a flat surface. I had to double check myself but I am correct. Was a while ago now though. I would not be afraid of using maths as all of electronics is mathematically modeled. When I was at university studying electronics they used to say if you don't like maths, don't do electronics. Electronics is maths, just a thought. Great work and great instructive videos and yes I have learned a few things, Particularly all the different uses of resistors in valve circuits. Fantastic delivery of the subject and easy to understand.

[@UncleDoug]

Thanks so much, Allister. You are correct about the actual meaning of the symbols.

[@telecomex]

Horses! Smiled all the way to the end. Great analogy. As always, many thanks for my ongoing education. 6 feet of separation greetings from the west coast of locked down Canada! ss

[@UncleDoug]

Thanks, SS. Glad you enjoyed it.

[@kevinski5386]

Thanks for all of your videos. I have learned a great deal. I built your current limiter to plug the amps into and also used your knowledge to build my grounding probe. I am glad you are going to build an isolation transformer for use on a bench. It took me a month to get the correct info on an isolation transformer. I learned that it is very, very difficult to find an actual isolation transformer. Almost all you can buy have the third safety ground connected from primary to secondary side through the chassis. There is NO isolation. It also does no good to disconnect the green safety wire on the side you plug into. It Always has continuity between neutral and safety ground. I found the outlet plugs you plug into have a internal strap you cannot break between safety ground and the chassis of the outlet. It is then in contact with the units chassis. I finally learned that an orange outlet with a green triangle is the only outlet you can install that the safety ground pin is not connected to the chassis. I put one of those in and finally got isolation like you show in your diagram. Later I learned that is what they call hospital grade. I await you video to see if there is anything else that I need to know on this subject or I have wrong.

[@UncleDoug]

You're welcome, Kevin. Wow, you really went through a lot of trouble trying to get an isolation transformer that actually functioned properly. The one I'm going to build will cost about $40 to $50 and will isolate the heck out of any amp circuit drawing 4A or less. Thanks for the input :)

[@billpowell5931]

I thoroughly enjoy your videos. Out of all the videos I have watched (some more than once) this is the one that clarifies the isolation transformer for me. I feel comfortable now to open the new transformer I purchased so I can verify the connections from the primary and whether or not it is a true isolation transformer. Thank you for sharing your knowledge and experiences.

[@UncleDoug]

You are quite welcome, Bill. We're really glad the video was helpful.

[@CraftAero]

Great video... In preparation for building some tube amps (found a baker's dozen of NOS Marconi Radiotron 6L6GCs) I built myself an isolation transformer with a switchable ballast load. Now I just have to save up for an oscilloscope [painful grimace]. Your channel and a small handful of others have been an immeasurable source of information. SOOOO glad I have the patience to do it right and didn't just charge in and start building without copious research.

[@UncleDoug]

Thanks, CA. It sounds like you're acquiring some nice equipment. Be sure to build a Current Limiter......it may be the most useful tool of all. I've posted a video showing how. Good basic used oscilloscopes can be had in the $200 and less range. The probes and accessories, however, can run up the bill a bit.

[@CraftAero]

Thanks Doug. "Current limiter" is what I meant by switchable ballast. Maybe a poor selection of terminology, but YES, I definitely have one. Being fairly deep in the "Great White North" used silly-scopes aren't locally available and the S&H / customs fees can double the cost. I'm leaning towards a Hantek 5xxx DSO. I want a stand-alone device so I'm staying away from PC USB types. Dang Electro-Boom keeps giving away nicer scopes but with his 1.6M subs... Lol.

[@UncleDoug]

You're welcome, CA. I understand that equipment is difficult to acquire in different parts of the world.....but it seems like you're doing a great job anyway.

[@chennemeyer]

That was fascinating, cleared up a bunch of basic electronic questions about the powers service and ground vs neutral.

[@UncleDoug]

I'm glad to hear that, Chuck.

[@rillloudmother]

Uncle Doug comes through with fact based content! Thanks Uncle Doug.

[@UncleDoug]

You're welcome, RL :) Thanks !!!

[@boonedockjourneyman7979]

Such an important topic. Thank you. The 10 M resistor is in the scope along with its bypass cap. You were pointing to a 10x, 100x, etc., multiplier in the probe. If it were 1M it would be a 1Mx probe.

[@UncleDoug]

You're welcome, BJ.

[@lroy730]

Great video ! I recently purchased a cheap Isolation transformer , and the ground from the input was attached to the Secondary Iso. Output . So I clipped out the Iso. Ground and it was safe and correct. This seems to be done this way in many cheap Iso Transformers so everyone should check and rectify it to make it safe.

[@UncleDoug]

Thanks, LR. I've heard so many horror stories about inexpensive isolation transformers (that didn't "isolate") that I'm going to build my own, just to be sure it does the job.

[@y2kroxy]

A question- If you built your isolation transformer in a metal enclosure and grounded the power input ground wire to the metal enclosure and If the isolation transformer secondary neutral is not grounded to chassis but connected the output to a duplex 3 prong receptacle to plug in DUT, isn’t the DUT plug grounded thru receptacle metal mounting tabs (that are directly connected to receptacle ground prong which is mounted to grounded metal chassis) ? Or is the isolation transformer not mounted to a metal enclosure or its secondary output not connected to receptacle?

[@shellygoldensteinberg4521]

More superb instruction by Professor Uncle Doug.

[@UncleDoug]

Thanks so much :)

[@tonymanns8249]

Doug, many thanks for advising people to keep one hand free of any electrical circuit and in their pocket However, it is MUCH safer to NOT have one hand in your pocket, it is MUCH SAFER to have that hand not touching ANYTHING.

[@UncleDoug]

Hopefully, when your hand is in your pocket, Tony, it isn't touching anything.....unless, of course, you're playing a little "pocket pool" :)

[@tonymanns8249]

I was an electrical tech for 30 years and I kept my free hand in my pocket until I received a shock. It can happen, even when not playing pocket pool. :)

[@UncleDoug]

Then I guess it's best to change methods and keep your hand in someone else's pocket :):)

[@davemassie3726]

Congrats on 50K, great iso vid and thanks for sunday morning car show without leaving the house!

[@UncleDoug]

Thanks, Dave. Glad you enjoyed the show :)

[@jjiacobucci]

A very helpful and illuminating video. Thank you Uncle Doug !

[@UncleDoug]

You're quite welcome, JJ :)

[@tinkerman9224]

I'm elated your doing oscilloscopes, I just acquired one, & learning about it. Thanks again your the Greatest !

[@UncleDoug]

You're welcome, TM :)

[@sebastiaanversluis]

Great safety refresh course about isolation transformers! Loved the red t ford pickup, very cool. Thanks!

[@UncleDoug]

You're welcome, Sebstiaan :) Glad you liked it.

[@donaldfilbert4832]

Great video Uncle Doug !! I look forward to the next video where you build a DIY Isolation Transformer !! Thanks !!

[@UncleDoug]

You're welcome, Donald :)

[@willievivanco1]

Oooh man you described this like no other.so simple to understand a pleasure to watch thank you

[@UncleDoug]

We're glad you enjoyed the video, Wilfredo.

[@HitchHiker4Freedom]

Excellent information Uncle Doug. Some real nice rods at the end to. Thanks for your time.

[@UncleDoug]

You're welcome, CC. Thanks for joining us.

[@matambale]

Nice 'barn sore electrons' analogy, Doug!

[@UncleDoug]

Thanks, M.

[@rustman777]

Thank you for this video. I'm looking forward to seeing the followup on building an inexpensive isolation transformer. I owe you for teaching me how literally every section and component of my tube amps work. I have a scope and signal generator that I have been holding off from poking around with because I knew part of the story that you've explained here. I want you to consider mentioning any potential (no pun intended) for additional danger when using a signal generator along with a scope in an amplifier circuit in a future video. Mine is a typical Chinese signal generator with a wall wart powering it. I don't know what I don't know. Thank you kindly!

[@UncleDoug]

You're welcome, RM. I will endeavor to make the oscilloscope presentation easy to follow and retain, and will do so with safety in mind. See you then :)

[@michaeldavidheit]

Great video, well taught... thank you.

[@UncleDoug]

Glad you enjoyed it, Michael.

[@judges69]

Great topic, can't wait.

[@UncleDoug]

Thanks, J :)

[@stevenjozefik659]

Hey Doug , This project is great , very beneficial for home recording studios as well .. And to go one better , a larger metal enclosure could incorporate a current limiting function with a couple of incandescent light bulbs that can be by passed with a switch.. I use one for trouble shootsing . saves me a lot of fuses.

[@UncleDoug]

Thanks for your nice comments and input, Steven.

[@robertgaines-tulsa]

Ground is not just simply a redundant neutral. Electrically, it is just that, but the neutral wire needs to be only used be used as the neutral return path while the ground needs to only be used as your earth ground. While the neutral wire is at 0 volts when it is not used, as soon as a device is powered up with that line, the neutral starts to carry 120 volts. You don't want your chassis or any other device using a ground to be connected to that. Under electrical code, the ground and neutral are only combined at your main power center. At no other time in your house, be it sub power center or device, should the ground and neutral be combined. (Old TVs may be an exception.) This keeps your ground safe to be used as a ground. In a ground fault situation, the ground will be temporarily used as neutral (hopefully). In a best case scenario, the hot becomes shorted with the grounded chassis or at least is draws enough current to blow your fuse or throw your circuit breaker quickly ending the dangerous situation. For times when the ground fault does not draw enough current to blow your fuse or throw your circuit breaker, the relatively new Ground Fault Circuit Interrupters (GFCI) in special receptacles and circuit breaker modules cut power when minute amounts of ground fault current are much too small to blow your fuse or throw your circuit breaker. One quick note about isolation: some cheaply made switching power supplies (generally made from China), are referenced directly to mains. So under certain conditions, your poorly designed phone charger could become a 120 volt nightmare killing both you and your phone! Thank you, China! NOT! Just be aware of that. It's mostly just with the dirt cheap stuff directly bought from China, but a multimeter can tell if your DC is referenced to 120VAC or not.

[@UncleDoug]

Thank you for your detailed and informative input, Robert. My intention in the receptacle diagrams, showing a connection between return and earth ground, was to remind viewers of the ground referencing that occurs whenever you plug an electronic device into one of those receptacles. Sometimes liberties are taken to facilitate understanding.......:)

[@priceamp]

yes, thanks for this clarification.

[@Todestelzer]

Every outlet in my home has the ground and n shorted because they build it cheap here in Germany after the war. It’s really annoying. Only in my bathroom it got changed a couple years ago.

[@russellstephan6844]

As mentioned above, grounding in a home wiring system serves one purpose. That purpose is to signal the breaker to trip. The breaker trips since ground and neutral are connected at the breaker panel. Pounding a grounding rod 10 feet into soil and making a live feed mains connection to it is not likely to trigger a breaker. It is an odd fallacy to lay people and the uninformed electrical professional that grounding somehow protects people directly. It only protects indirectly by tripping a breaker and ceasing power to that particular house circuit. Check out the MikeHoltNEC KZbin channel. Grounding, equipotential ground planes, etc., are covered in-depth. It's fascinating stuff!

[@okaro6595]

The neutral has same current as the live but not the same voltage. The voltage is lost at the device. The voltage is just a few volts depending on the load. I measure about one volt on my TN-C ground contact when the microwave is on. Phone chargers are double insulated- They do not use the ground contact at all. Sure there are some very dodgy Chinese chargers. Never buy a phone charger directly from China. You life is worth more than the few bucks you save.

[@BryanByTheSea]

Excellent video, have seen others on the same subject and they had me scratching my head.

[@UncleDoug]

Thanks, Bryan. I hope this video and the oscilloscope videos are easy to comprehend. All of these topics have been covered before by others who know more that I do......but, as you said, not much of it generally makes any sense.

[@acceler9]

Thanks for the great video!! Truly, the best explanation I've seen!!!! I wish I has this several years ago when I was building my own isolation transformer.

[@UncleDoug]

You're welcome, A9. I'll be building my own in the near future, and hope it turns out OK.

[@jeffbenson6102]

Thanks for grounding us with this valuable information. I am looking forward to the oscilloscope tutorial.

[@UncleDoug]

Thanks, Jeff. We'll see you then...............

[@josephmartinez3851]

First... Uncle Doug is awesome..

[@UncleDoug]

You are too kind, Joseph. Thanks :)

[@rb032682]

Good stuff, Uncle Doug.

[@UncleDoug]

Thanks, RB.

[@L0vetube1]

Electron indeed our horses... Good vid btw...

[@UncleDoug]

Thanks, David.

[@33jwilliams]

Congratulations Uncle Doug on 50K subscribers! You deserve each one and more.

[@UncleDoug]

Thanks so much, Jeff.....for your comment and your subscription :)

[@stevenjozefik659]

Sad how some of those secondary horsies have to get dissipated though . great to see you still punching out great video learnings Doug ..

[@UncleDoug]

Thanks, Steven :)

[@jorgemellooliveira9611]

ótima aula aqui onde moro tudo é aterrado e nossa tensão é de 220 Volt maior perigo é rompimento do neutro 0 volt aquele poste que o Sr. mostrou é um risco romper o terra gostei das instruções obrigado por comentar um abraço mestre

[@UncleDoug]

Muito obrigado por seus comentários agradáveis, Jorge. É sempre bom ouvir de você.

[@Scorpio722]

Great overview for the isolation transformer. Please, remember the "left hand rule" too. In one of your video's on the current limiting lamp, I had a cringe moment as you used you left hand to short out the hot line via the lamp...ouch! lol!

[@UncleDoug]

I didn't want to risk my right hand ;)

[@bryantay11]

Great work as usual, UD. One suggestion: on a practical level, when buying an isolation transformer (new or an used one off eBay), it’s important to stress that many products that may be easily confused for an isolation transformer are actually autotransformers that provide no isolation at all. This is especially true of the variable transformers that are widely available. These are often mislabeled as “variable isolation transformers”, when they are nothing of the sort. In addition, some products such as the old RCA Isotap units have both an isolated secondary winding and an autotransformer winding (often with variable voltage). Folks should be aware of the differences and know never to use the variable side when trying to isolate an amplifier (or anything else) from the mains power. Once again, great work and thanks for all you do! Bryan

[@UncleDoug]

Thanks for bringing this to our attention, Bryan. You make an excellent point. It's my intention to build an inexpensive I.T. in my next video. If viewers follow my design, they will avoid the pitfalls of misrepresentation in the marketplace. I will endeavor to make your points known to them at that time.

[@bryantay11]

Great idea, Doug! Looking forward to seeing what you've come up with. Take care!

[@wildbillhackett]

I've still got a '97 Dodge Ram work truck. The motor sits back on that too, and not only does the cap sit in the back, but the air filter (a real pain to change on Dodge Rams) sits over the top of it and must be removed before you can even change plug wires. I'm 6'4" and even I have to stand on something to reach that cap. It's a great running truck with 255k miles and counting, but on the rare occasion I have to work on it, nothing is easy.

[@UncleDoug]

It's a shame they don't generally design vehicles to be worked on, Bill. I've heard horror stories of engines actually having to be lifted up from frames to allow spark plug and exhaust manifold work.

[@bigmac4948]

Thank you for demystifying this potential shocking topic Uncle Doug!!

[@UncleDoug]

You're very welcome, Big Mac.

[@ronsmith7598]

GREAT Explanation! I'm a retired EE after 44 years. Never thought about this as all I did was DC chips. Setting up a hobby bench now so I started looking into this. The Iso transformer I just bought is Tripp-Lite 1800 Watts. Figure It'll handle anything I throw at it. The secondary Ground terminal in it is NOT tied to the Neutral, but is tied to the primary side of the ground terminal. After watching your explanation, I think I better disconnect it from the secondary outlets completely. Correct? BTW, LOVE the pace and quality of your series. Just subscribed! Thanks!

[@UncleDoug]

Greetings and thanks so much for your nice comments and for subscribing, Ron. You can leave it attached and use an adapter to eliminate the ground lug on the circuit to be tested, or detach it so no earth ground is provided to the circuit tbt.

[@michaelkoch5613]

A wealth of information, as always. There's an ongoing discussion on TDPRI.com regarding grounding, and much of your explanation of ground reference is quite relevant. Thanks again, Uncle Doug!

[@UncleDoug]

Thanks, PS. I intend to build an IT and test it thoroughly in the near future. Hopefully, I can come up with facts instead of supposition......keep your fingers crossed :)

[@dannyyorri2345]

Great analogy. Thank you !

[@UncleDoug]

You are so welcome, Danny.

[@andersf324]

As always, I await your excellent posts with bated breath. I'm happy to see that Jack's uncanny concealment skills are getting even better! Great analogy with the horses. I saw the comment regarding three phase. I grew up in Sweden, which is a 400V, 50Hz system and you can have either 3 or 4 wire grid connections. The interesting thing is that with true three phase (as we had in my house growing up) you can get truly incredible efficiency with appliances that contain three phase motors. The three phases from the grid are guaranteed to be at a 120 degree triangular phase difference, so when you have a motor with the coils at the same configuration it really increases the efficiency, sort of like a multi-cylinder motor with a properly offset crank. Also, transmission lines are configured in a triangular configuration to eliminate losses. The other interesting aspect is that you have a floating null configuration for your regular 220V outlets. What this means is that the relationship between plug and receptacle configuration is different than here in the US. Most outlets there are non-grounded, EXCEPT where the area you are wiring requires grounding, such as basements or wet areas. A non-grounded plug will not fit in a grounded outlet unless the apparatus is double insulated (indicated by the standard double square symbol). If so, it has a universal plug that can fit either grounded or non-grounded outlets.

[@UncleDoug]

Very interesting input, Anders, particularly the part about 3-phase power being the norm for home use....and it's efficient application to 3-phase motors, with the phases at exactly 120 degrees apart. Such a power supply is not routinely supplied in the U.S. except to special locations that require it.....like the huge compressors for refrigeration units in grocery stores.

[@andersf324]

Yes, absolutely. I tried to get a 3-phase connection for one of the properties I had here in Florida and the costs where prohibitive due to the standard 2-line distribution for the HV lines. It simply wasn't an option. I think the quote was 50-60+k to pull a new feed from the closest 3-phase point.

[@UncleDoug]

Wow, expensive !! They've got it made in Sweden :)

[@dhelton40]

A really great explanation of grounding in power wiring. I sure hope it doesn't give any one the idea that connecting a three wire receptacle to the white wire in a receptacle box where there is no ground wire is ok. Doing this will result in high voltage on the metal frame of devices plugged in, in the event of an open neutral (white wire) anywhere in the system. I will point out that in the real electrical system of you home or office that the green grounding circuit and the white grounded conductor are only connected (bonded) at the service equipment. This maybe the buss bar in your breaker box (in older homes) or the a meter box with a main breaker (in newer homes) This is also the point where ground rods and water pipes will be connected. I mention this because I have seen this done by DIY house flippers. It will make the plug in testing device used by home inspectors show the receptacle to be good when it is not!

[@UncleDoug]

Thanks for your helpful input, DH.

[@elmakednos]

Thank you very much for the video and your response. I have watched it many times.This is one of the most important videos for our own security. I did not buy an isolation transformer till now, so I use the multimeter before make an oscilloscope measurement for safety. But I will try to buy one (A 500 watt transformer will do it) for about 55 euros or 65 usd. Unfortunately there is room space problem. I own an old but very good 2 channel cro oscilloscope.

[@UncleDoug]

You're welcome, MP. I am currently uploading another video covering the design, function, and safe use of Isolation Transformers with Oscilloscopes. I think you will find it quite interesting.

[@orinlowe1128]

Fantastic...Thanks Uncle!

[@UncleDoug]

Our pleasure, Orin.

[@tomfrye9037]

Thanks for reminding me, Doug. Two things I lack...isolation transformer and a scope. I have a variac that comes in handy...but it sho don't isolate. I'll keep my eyes pealed...Lookin' forward to the next installment(8-).

[@UncleDoug]

You're welcome, Tom. I get along just fine without an oscilloscope in most repairs, but there are certain circuit problems that arise (i.e. oscillation) which can only be visualized or identified with a scope.

[@tomfrye9037]

WHACK! That was me hitting myself on the head. I just saw the lad who was my boss before I retired and I forgot to mention any of this stuff. DUH! He gets into electricity and electronics some, but not near like he used to. He might have duplicate items he'd be willing to sell or trade. I'll catch him next weekend. And yeah...oscillations and phase distortion...particularly crossover distortion on push pull outputs. In the past, I've cleaned c.o. distortion up pretty quick when I could see what I was doing.

[@MauroSedrani]

As always, a fantastic and instructive video. Thanks Uncle Doug!

[@UncleDoug]

You're welcome, Mauro :)

[@MauroSedrani]

Sorry for the typo :)

[@deankq4adj125]

Just found this channel. Awesome stuff and even better information! Thank you sir!

[@Fixologist1]

Another great video, Doug. This actually reminds me, I have been meaning to build an isolated variac. The one I use isn't isolated. I get by with it fine, but no sense testing fate.

[@UncleDoug]

Thanks, Brad. I've never considered the combination of an isolation transformer and a Variac, but it sounds like an interesting project. Let us know how it turns out :)

[@thomasmaughan4798]

@@UncleDoug I used one in high school. The wiper touches every other turn, the secondary windings, on the core and the primary turns are interleaved with secondary turns. So it achieves isolation and variable voltage in the same device.

[@UncleDoug]

@@thomasmaughan4798 Very interesting, Thomas.

[@peteb2]

Love your presentation and especially the hotrods. Real interesting to see how your Mains electricity is reticulated in the USA. I don't want to hoopa-doop things on symbols but i was always taught the "upside down christmas tree" represented zero potential Earth Ground and indicated a point for electrical shock protection, the bent pitchfork = Chassis ground and in signal paths a triangle apex pointing downward was signal/common ground.

[@UncleDoug]

Thanks, Pete. I think there is a lot of confusion about the literal meaning of the symbols. If you look at amp schematics, you will see all sorts of aberrations. I clearly defined my symbols in the video to avoid confusion and thought the "rake" would be easier for viewers to associate with the "E" in earth ground.

[@bbmade]

Really, really helpful video Uncle Doug. I need to build and isolation transformer very soon. Looking forward to the next video and info on oscilloscopes. I want to get more use out of mine.

[@UncleDoug]

Thanks, BB. Stay tuned for an economical isolation transformer build as well as the oscilloscope series.

[@sailingeden9866]

The neutral and the ground are only supposed to be connected inside the breaker panel. If you connect the neutral to the ground at the outlet, that is called a bootleg ground, and is a code violation.

[@UncleDoug]

You are correct, ICU. The diagram was not intended to be a full and accurate representation of the entire wiring scheme of most homes.

[@davidware7428]

Great as always, Doug. Keep 'em coming.

[@UncleDoug]

Thanks, David. We will :)

[@TheOpenAirGarage]

Great information. Looking forward to the rest of the series. Really nice cars at the show.

[@UncleDoug]

Thanks twice, T :)

[@bigfoottoo2841]

Here's one for you. In normal operation, no current at all should ever flow through the green wire. However, many amplifiers use the green wire as a return for 120 volt circuits such as blower fans while operating off of 240 volts AC. They should be using a 4 pin plug with a neutral line for 120 return current. Currents through the green ground wire will create ground loops. Another, current through the ground wire from the service panel to the ground rod will never conduct enough current to blow a fuse. The purpose of Earth ground is to shunt any static electricity off of the power feed, this keeps it out of your house. If one were to raise the secondary ground of the pole transformer the entire house would be isolated from Earth ground but there would not be any protection from static charges coming in from the power grid. At the service panel, the neutral wire and the green wire are both bonded to the ground bus bar. Current coming from a short down the green wire is passed out to the common wire which will conduct enough current to blow the breaker...

[@UncleDoug]

Thanks for the detailed analysis, BF2.

[@paultopolski1978]

Thanks for the very informative video on the isolation transformer. I am really looking forward to the oscilloscope video. It is hard to find good videos on the O scope that cover the basics needed for amplifier repair.

[@UncleDoug]

You're welcome, Paul. I too hoped that good basic oscilloscope videos were readily available.....but, like you, I discovered that within a few minutes, they all tend to wander off into some alternate reality that confuses, rather than illuminates.

[@jackallen6261]

As an aside with nothing to do with amps, since we are talking about house wiring if anyone thinks they are paying too much for electricity compared with say their neighbors, have a qualified electrician check the load balance on your house. You may have say 65 or 70 percent of the normal daily load running on one leg and only 30 or 35 percent on the other, your electric meter only looks at the highest load and doubles it for your usage , so you may be paying too much. This is especially noticeable since many people have switched to LED light bulbs which use much less current than say incandescent bulbs. It's worth having it checked by an electrician.

[@UncleDoug]

I never heard of this before, Jack. I'm sure everyone's electric bill seems too high. Thanks for the tip.

[@marklange8894]

My phone buzzed and I was alerted to another great video that you had posted. So I sprinted to the living room (as fast as my Cobalt Chromium Molybdenum Steel right knee will allow) and watched your latest video. One suggestion I have is that you might mention and explain the dangers of ”non-polarized” power cord plugs and how plugging in your vintage guitar amp on one side of the room and your vintage PA amp on the other side of the room could potentially apply 240 Volts AC to your lips and hands if you touch the guitar strings and microphone at the same time. Also doesn't replacing a two wire power cord with a three wire cord defeat the isolation characteristics of the transformer in an amp with a transformer making it as hazardous as a transformerless amp? (assuming that there is ground referenced components or center taps in the circuit). Because you would effectively be earth grounding the isolated chassis. But that is the reason for using isolation transformers. I built mine from a used industrial control transformer that I got off of ebay, cheap, and got the added benefit of isolated 120VAC and 240VAC outputs. I have a 0-600 VDC power supply 500 mA that operates with 240 AC input so that worked out great and if I run across any great deals on non-North American equipment I have the mains power available for it. I almost expected Herman Munster to step out of the ”Tall Model T Pickup”. Some beautiful cars.

[@UncleDoug]

The non-polarized power cord and equipment connected to different outlets problems were already addressed in my Shock Hazards video, posted several years ago, Mark. A three-wire, chassis-grounding power cord provides an earth ground for any stray primary electrons that find their way from the primary circuit to the chassis.....instead of you (as long as you aren't grounded). It has no benefit or effect on the secondary circuit. Isolating the primary with an isolation transformer eliminates the ground-reference risk and makes the primary as safe as the secondary.

[@marklange8894]

On the isolation transformer I totally understand and agree, that is why I have one built into my bench. But now I am confused about the actual safety factor of a 3 wire cord retrofitted into an amp that has a transformer as opposed to an amp without a transformer. Ok, let us say that you measure the plate voltage of a 6V6 in say a Fender Champ with reference to chassis ground you would see what voltage, 325 Volts DC approximately? If that chassis had a been retrofitted with 3 wire cord would that not also reference that plate voltage to earth ground. Just like the transformer-less amp? If you measured the plate voltage of an amp with a two wire cord to earth ground, I would not expect to see anything DC on the plate referenced to earth ground, because the only connections in the primary are to the primary windings of the transformer and possibly a ”Death Capacitor”, thus providing isolation from earth ground. I would expect to see B+ referenced to the chassis. Am I missing something here? Adding the earth ground wire could protect you from a shorted component but by the same token defeats any transformer isolation from earth ground on the secondary side that the two wire circuit had. Am I just confusing myself? (wouldn't be the first time)

[@UncleDoug]

The three-wire power cord grounds the chassis for safety against any leakage to chassis ground in the primary circuit only. The grounding of the chassis has absolutely no influence on the secondary circuit, since it is isolated by the P.T. and has no ground reference. Earth ground is meaningless to the secondary circuit: both DC and filament AC voltages.

[@marklange8894]

This may be my MS damaged brain getting in the way here but this is how I am seeing it in my mind. The chassis of the amplifier is DC ground for the amplifier. The moment that an earth ground wire is connected to that chassis that makes DC ground and Earth Ground at the same potential. That would make all chassis referenced voltages in the secondary also earth ground referenced. The only way that I can picture having isolated secondary with an earth grounded chassis would be if the amp had an isolated signal ground like a differential instrumentation amplifier. (Which I do have some experience with some Honeywell tube type differential instrumentation amplifiers in roll type chart recorders) those had a signal input and signal ground that was independent from earth ground, chassis ground and even independent of AC neutral. The DC on the tubes was not chassis referenced, there was a signal ground buss and the chassis was earth grounded to the rack with the rest of the equipment. That is all I am saying, when the chassis is at earth ground potential, if the DC ground is the chassis it would also be at earth ground potential. Primary, secondary, it would not matter, only secondary outputs that had no chassis connections would be isolated.

[@moodyga40]

great video

[@UncleDoug]

Thanks so much, Ian :)

[@alphabeets]

This is an excellent explanation. Well done!

[@UncleDoug]

Thanks so much, AB :)

[@EzeeLinux]

Fantastic video! I LOVE your Electron Horses analogy. Where were you thirty years ago when i was studying this in radio engineering class? :)

[@UncleDoug]

Thanks so much, Joe. I was probably out drinking and raising hell ;)

[@EzeeLinux]

So was I... That;s why this was so cool. I finally got it! LOL :)

[@UncleDoug]

Darned right, Brian.......someone has to do it :)

[@stumacdonald1234]

ZZtop and most Texans I'm told! lol!

[@UncleDoug]

It would be a great honor to have Billy join us in our favorite pastime :)

[@prestonshute7243]

Excellent video, your video just might save a life. 73 wd4dda

[@UncleDoug]

Thanks, WD. I hope so :)

[@lieselottemeier1811]

Hey Doug, first of all: A thousand thanks for your phantastic videos - I really love your work! With this specific video, I need to send some criticism, though... From about 10 mins onward, you explain, why it's not so dangerous to work on the secondary side of an amplifier, as the circuit is insulated from the primary side via the power transformer. Of course, in this specific schematic this is correct, but in 99% of all amps I'm working at, the secondary side of an amp of course is also ground related - and therefore it is extremly dangerous to also only touch ONE part of the secondary side of almost any amp, as long as it's not comletely insulated with the use of an external insulation transformer. I know, that I don't have to expain this to you, you know exactly what you're doing. It's just the situation, that somebody who watches this video might think: "oh, cool, I got proper insulation from my PT anyway, so I'm safe, fumbling around in my amp, as long as I do not touch anything in the primary section...!" Which of course is extremely wrong and dangerous... Anyway: Please go on with your great work, and all the best to you and your furry housemates!! :)

[@UncleDoug]

Thanks, LM. I don't agree with your analysis of the secondary circuit in "99%" of amps, but I applaud your concern for safety. I would never encourage anyone to touch any part of a live circuit, but I espouse the "One Hand in the Pocket" rule when dealing with the secondary circuit. As long as you do not complete a circuit through your body by touching two points of different potential, i.e. with two hands, you will be OK in case of inadvertent contact. On the primary side, however, the one hand rule doesn't work.......especially if you are grounded.

[@lieselottemeier1811]

@@UncleDougHey Doug, In almost every case, when NOT using an insulation transformer, your amp chassis is related to ground. And as your secondary circuit is also related to your amp chassis and therefore to ground level, all your B+ and other high voltages are also related to ground level as well... So if you're NOT using an insulation transformer, it is really dangerous to touch any part of the secondary part of an amp, even with only one hand... Tell me if I'm wrong, but imho this should be a fact... and not even an "alternative fact" :D Anyway, I use a combination of insulation transformer and variac with every amp repair I do at my workshop, and I even tested it just recently (with an device tester, that checks for insulation and also for the ground resistance) - and it all works absolutely safe.