Isolation Transformers
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- Опубліковано 9 чер 2018
- This video presents a thorough discussion of why isolation transformers are able to provide protection against shock hazards while working on electronic equipment, using transformerless amp circuits, and/or operating an oscilloscope. In the next video, we will build a basic, inexpensive isolation transformer.....so stay tuned.
CLARIFICATIONS:
1.) This video shows 120VAC (mains) circuitry. The general principles of ground referencing for 240VAC mains circuitry are basically the same.
2.) 35,000 VAC is a maximum for primary transmission. Normal primary voltage in residential areas is much lower.
3.) Words were clipped regarding out-of-phase receptacles in our homes........they are of no consequence.
4.) If all three of the secondary wires are utilized, the result is 240VAC, i.e. for ovens, home and water heaters, etc.
5.) Any circuit which is "earth ground referenced" (EGR) can be shorted to earth ground by test equipment, the human body, etc. The "horses" originate from the pole-mounted transformer and will gladly use any opportunity, or short cut to return to it. Once isolated from "mains" EGR, electrons have no affinity for earth ground and tend to remain, happily and safely, in their own circuit.
6.) The diagram showing a connection between ground and neutral/return in the receptacles is not literally true. The actual connection is made in the distribution panel (DP) of the structure, not in the receptacles. Since I did not cover the DP in the video, the connection had to be presented this way. In retrospect I should have mentioned this and used dotted lines in the diagram. I apologize for any confusion.
Here are links if you wish to become a patron of our advertising-free channel: / uncledougsvintageamps or if you wish to make a PayPal donation to dldcam@aol.com Thanks for your support !!!
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 !!
Congrats on the 50K milestone. I think it just means 500K - 1M folks out there still havnt heard of you before. :-)
Cheers Uncle Doug!
Thanks, Lee. I guess we'll just have to win them all over :)
One day I'll thank you by giving a ride on one of those cars.
Sounds good, Ben.
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.
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.
Wow....thanks so much :)
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.
I hope it's helpful, Capt.
@@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?
@@captainfineweather5610 All those numbers make me dizzy, Capt. Just try it and see. Good luck.
@@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.
@@captainfineweather5610 Apology accepted, Capt. How did the experiment turn out ?
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!
You're welcome, Sting. Stay healthy :)
I love seeing Jack again, due to the persistence of video images, or at least I saw his outline under the blanket. 🙂
Jack appreciates your interest and support, Jeremiah. Thanks for your input.
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 UA-cam guy.
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.
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
Thanks, George. Cemeteries are full of people who got too careless :)
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.
You're welcome, Morik. I'm glad it was clear and helpful.
Great as always, Doug. Keep 'em coming.
Thanks, David. We will :)
Just found this channel. Awesome stuff and even better information! Thank you sir!
Congratulations Uncle Doug on 50K subscribers! You deserve each one and more.
Thanks so much, Jeff.....for your comment and your subscription :)
Great safety refresh course about isolation transformers! Loved the red t ford pickup, very cool. Thanks!
You're welcome, Sebstiaan :) Glad you liked it.
Doug, many thanks for your videos that take great care to teach everyone about both the joys and the extreme dangers of electric circuits.
You're welcome, Tony :)
Congrats on 50K, great iso vid and thanks for sunday morning car show without leaving the house!
Thanks, Dave. Glad you enjoyed the show :)
Best explanation I’ve seen on UA-cam. I love the electron horses analogy, very visual, giddy up!
Glad you liked it, BB. Off-the-wall analogies tend to stick with us longer :)
Excellent information Uncle Doug. Some real nice rods at the end to. Thanks for your time.
You're welcome, CC. Thanks for joining us.
Another Great video Uncle Doug!! Jack's videography is truly unrivaled
Thanks so much, Joe. I'll tell him.....if I can find him :)
Thanks for grounding us with this valuable information. I am looking forward to the oscilloscope tutorial.
Thanks, Jeff. We'll see you then...............
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.
Thanks so much, BJ.
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!
Glad it was helpful, E.
That was fascinating, cleared up a bunch of basic electronic questions about the powers service and ground vs neutral.
I'm glad to hear that, Chuck.
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.
You're welcome, A9. I'll be building my own in the near future, and hope it turns out OK.
Great information. Looking forward to the rest of the series. Really nice cars at the show.
Thanks twice, T :)
A very helpful and illuminating video. Thank you Uncle Doug !
You're quite welcome, JJ :)
As always, a fantastic and instructive video. Thanks Uncle Doug!
You're welcome, Mauro :)
Sorry for the typo :)
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.
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.
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
You're welcome, Jack. A coincidence??? I think not :)
Oooh man you described this like no other.so simple to understand a pleasure to watch thank you
We're glad you enjoyed the video, Wilfredo.
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
You're welcome, Luther. I'm glad to hear that the videos are helpful :)
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.
Thanks, Curtis.
I'm elated your doing oscilloscopes, I just acquired one, & learning about it. Thanks again your the Greatest !
You're welcome, TM :)
Excellent video, have seen others on the same subject and they had me scratching my head.
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.
Awesome video! I am excited about the isolation transformer. Keep it up.
That's great, Steve. We will :)
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.
You are quite welcome, Bill. We're really glad the video was helpful.
Great video Uncle Doug !! I look forward to the next video where you build a DIY Isolation Transformer !! Thanks !!
You're welcome, Donald :)
More superb instruction by Professor Uncle Doug.
Thanks so much :)
Thanks for putting me in the Saddle on the Isolation Transformers. Your a Fantastic Mentor.
Glad you enjoyed the video, BM :)
Uncle Doug comes through with fact based content! Thanks Uncle Doug.
You're welcome, RL :) Thanks !!!
Thank you for demystifying this potential shocking topic Uncle Doug!!
You're very welcome, Big Mac.
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.
Welcome aboard, Grant. Brad and I are old cronies.....so you should feel right at home.
Uncle Doug just answered questions that
no one has been able to answer me in years
We're glad the videos are helpful, Matt.
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.
Thanks, Gerald. Glad you enjoyed the video.
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?
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.
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
You're welcome, Jim.
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.
You're welcome, MS. Glad you found the video to be informative.
This is an excellent explanation. Well done!
Thanks so much, AB :)
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
Thanks, SS. Glad you enjoyed it.
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!
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 :)
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.
You're welcome, M47. Thanks for your nice comments.
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.
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.
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.
Thanks, BB. Stay tuned for an economical isolation transformer build as well as the oscilloscope series.
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
You're welcome, Brent. I'm glad it was helpful.
Great lesson and great cars!
Thanks, MO :)
This should be a very interesting series,,, Thanks pal.
You're welcome, Carl :)
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.
You're welcome, Mike. You are correct with regard to the importance of this issue, and we wish you the very best.
Excellent job, sir. My respect!
Thanks, Fabio. I appreciate it.
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.
You're quite welcome, Phil. Thanks so much :)
Great topic, can't wait.
Thanks, J :)
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!
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.
Great analogy. Thank you !
You are so welcome, Danny.
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.
You're welcome, Jack. Horses are dangerous at both ends :)
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.
You're quite welcome, Cass. It's always good to hear from you :)
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.
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 :)
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!
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 :)
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.
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.
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.
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.
Great tutorial Uncle Doug!
Thanks, RS :)
Very helpful and informative. Thank you
You're welcome, LM :)
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.
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.
@@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!
Nice 'barn sore electrons' analogy, Doug!
Thanks, M.
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!
I didn't want to risk my right hand ;)
Excellent video. Hats Off dear Sir.
Thanks so much, Godfrey :)
Great video, well taught... thank you.
Glad you enjoyed it, Michael.
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.
Thanks so much, Allister. You are correct about the actual meaning of the symbols.
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.
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.
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?
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.
Thanks for your nice comments and input, Steven.
Sad how some of those secondary horsies have to get dissipated though . great to see you still punching out great video learnings Doug ..
Thanks, Steven :)
Fantastic...Thanks Uncle!
Our pleasure, Orin.
Good stuff, Uncle Doug.
Thanks, RB.
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.
You're welcome, BJ.
The packaging had me rolling!!! Great pre-req to the o-scope stuff. Looking forward to that series.
That's good to hear, SS. We're looking forward to it too :)
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.
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.
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.
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.
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.
Wow, expensive !! They've got it made in Sweden :)
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!
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.
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.
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.
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.
It sounds like a neglected amp found a good, appreciative home, Chris. You are both fortunate :)
Hi Uncle! Still no Isotrans in sight, at least none that would fit in my purse. But, comes a time! I'll report back.
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.
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.
First... Uncle Doug is awesome..
You are too kind, Joseph. Thanks :)
This is just a f&@Kim amazing video. This teaches understanding thank you Doug
Thanks. Glad you enjoyed it, Stephen :)
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.
Then by all means create such a diagram, BB. We would love to see it.
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
Muito obrigado por seus comentários agradáveis, Jorge. É sempre bom ouvir de você.
Beautiful.
Thanks, Paul :)
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
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.
Great idea, Doug! Looking forward to seeing what you've come up with. Take care!
Hi Uncle Doug,
Congrats to 50000 subs!
Although it's safe for the oscilloscope to connect the ground clip anywhere in on primary side when using a isolation transformer, it can be very hazardous for the user when the probe ground is connected o the black / hot wire of the amp. The whole amp chassis will have the full 120V potential versus ground in that case.
Regards,
Thomas
Thanks for the tip, WW. I can't visualize any purpose or time that one would intentionally attach a probe ground to an AC hot wire......but now you have provided an even more compelling reason to avoid it.
Another amazing video. Thanks to my newest Uncle -- Doug!
You're welcome, Bob :)
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.
Hopefully, when your hand is in your pocket, Tony, it isn't touching anything.....unless, of course, you're playing a little "pocket pool" :)
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. :)
Then I guess it's best to change methods and keep your hand in someone else's pocket :):)
Thanks Unka!
You're welcome, Riloh.
That was great. Wow.
Thanks, Keith.
@@UncleDoug no thank you this is a topic that scares the crap out of me coz if felt what it's like to get a bang of mains. Very lucky it wasn't bad. You also never forget a shock what ever is about them. So thank you Doug 🙏👍👍👍
great video
Thanks so much, Ian :)
Excellent video, your video just might save a life.
73
wd4dda
Thanks, WD. I hope so :)