The Videx Soft Video Switch for the Apple ][+, a MOS 8701 replacement, and an isolation transformer

[@nhand42]

Dave Jones is a national treasure. Two thumbs up.

[@darrellaldrich8334]

This video of Videx products bring back many fond memories for me. As Videx's Software Engineer for these products, they are an important part of my life.

[@MegaWildweasel]

a nice refresher on VA and bench safety. been 40 years since electronics school.

[@uziel25]

Bob Ross of computer repair. Found your channel about a month ago. Probably from your collaboration with the Commander x16 project. Great videos with excellent knowledge of repair. At 1:30am it just hit me why you are so awesome to have running on my second monitor when playing Minecraft; its your voice and the way you laugh off anything that goes wrong. The late Bob Ross had the same presentation during his content (oil painting) and he was very very popular and dare I say loved. Thank you for the chill content!

[@stevesether]

Thanks for a great explanation of power factor. I've read the typical Wikipedia article on PF before, but the typical science article in Wikipedia (especially physics) assumes you already know how it works. e.g.. "the current flow is partially out of phase with the voltage" Which while true, is completely useless unless you understand what "out of phase" means, which most people don't. Now, I do know what out of phase means, but seeing a graph of the spiky current flow alongside the voltage really drives it home and nicely illustrates that the "out of phase" really just means that the current flow can just be extremely messy and complicated. Years ago I worked for a company that works to lower companies power bills, and one of the engineers gave a talk about the things the company did to do this. One of factors for pricing a large industrial power user is PF. The engineer tried to explain PF by a hand waving exercise that compared it to the foam in a beer. An utterly useless analogy that gives you no real explanation beyond "you're wasting something", and no insight into what's happening. He mumbled something about how it was "too complicated" to explain, and thus his hand waving analogy. Had he drawn a simple picture like you provided, I think he could have made a lot more people understand at least something about PF.

[@ExStaticBass]

Having mentioned that you like cars and such I'd like to recommend a channel that I really like along those lines. Cars and Cameras is a channel devoted to making improvised vehicles and repairing older cars and trucks. John and Ike are good people and they're trying to hit 1 million subscribers or maybe it's a hundred thousand. I can't remember at the moment but it's a fun channel to watch. I hope you enjoy it as much as I do.

[@cairsahrstjoseph996]

One of my favourite series on KZbin. Your enthusiasm is cheery too!

[@iocat]

As someone who's sent something in, it's definitely suspensful waiting for your item to show up! But fun when it does!

[@GreenAppelPie]

You’re absolutely correct regarding the power of KZbin. I’ve learned so much from it.

[@brainisfullofnonsense8183]

I was hoping that you were going to show the monitor hooked up to the isolating transformer which was then plugged into the same meter and then into the wall socket or extension cord. That would have let us see how the transformer changes the power factor that your house and the grid sees. Still, another great episode. Thanks. The Apple IIC and E are what we had growing up. Dot matrix printer and a DAISY WHEEL printer (I know, fancy right?). I can't tell you how many hours I spent typing in programs from Home Computing Magazine. But, it is what helped my aptitude for programming progress so quickly later on when schools finally started teaching it. So, not a total waste of my time. Another reason to use an isolating transformer (especially for medical equipment) is that it delivers a less 'noisy' power to the device, and sensitive instruments hate noisy power. A light bulb was a good example, but because most filaments are coiled (very very small diameter, but still there) they do have an inductive component and so don't end up with a perfect power factor either. Straight tube electric resistance heaters (like in water heaters) are as close as we can get to the theoretically possible P.F. of 1, but because even they have a bend or turn end up being less than perfect. Things that are hooked up to the grid with sub perfect power factors end up producting noise, or something that causes the voltage sine wave to become distorted. Sometimes this is done on purpose, such as when smart meters use the 60Hz signal as a carrier (reference voltage) and inject a MHz signal on top of it (only a few volts, and really fast modulation make it not apparent to most things like motors and such).

[@lordmmx1303]

Thumbs up for what you said before intro. awesome. I like that you go trough packages and take time to show them and talk to them. I really enjoy these series.

[@Steven_VE9SY]

Been 30 years since I got my amateur radio license. That was a nice little refresher course in electricity. I remembered every bit of it as you talked about it (Mostly). But had you asked me before I watched this, I would have shrugged my shoulders.. I wish we had phones with apps like that 30 years ago..

[@Drewsalems_Lot]

Hi Adrian from South Australia too! I enjoy your enthusiasm and in depth knowledge of pretty much anything. We had Apple IIe at school, then Amstrad CPC 6128, then Mac Plus. I grew up programming LOGO and BASIC 35 years ago. Love your content. Thanks for all your effort from all us Aussies! I learn a lot each week. Drew 😃

[@BarnokRetro]

Thanks for sharing that you dropped the IC and stepped on it. It's good to know that I'm not the only guy to pull that kind of goof!

[@nickwallette6201]

Oh, no. I’ve done some mighty dumb things when working on projects. I would wager any of us here who own both a screwdriver and a soldering iron have sent parts to the landfill unintentionally and prematurely. That’s part of the risk of doing anything interesting.

[@jonathancombe9991]

Thanks for the explanation of the Power Factor, I learnt something new. I do remember from Physics lessons (over 20 years ago), the IV=W formula (which my teacher told us to remember as the name "Ivy Watts", well it works because I still remember it even though I've not used this knowledge in at least 20 years).

[@terryraymond7984]

All we had in High School was Apple II's I had never seen this in 80 column mode. Awesome

[@alphaLONE]

Surely "Adrian's Mechanical Garage" would be interesting too!

[@bobdole57]

You did an excellent job explaining the power factor stuff

[@Craig1967]

That was an excellent explanation of Power Factor when using switching power supplies! I have understood PF when working with inductive and capacitive loads since the 90's, but never quite was able to visualize the PF in a switching supply. Thank you!

[@minombredepila1580]

Adrian, loved your new oscilloscope. Quite retro!!

[@francoisfritz198]

easy to see your totally in love with your Apple+! nice to see it, take care

[@christophermclarksr5965]

Watching Dave jones improved my soldering skills 100 fold..

[@Dorff_Meister]

Your Watts, VA, PF explanation was helpful. Thanks.

[@jasonbass2973]

One of my favorite car shows is Vice Grip Garage!

[@xyzconceptsYT]

Wow, another MCM fan, you just got some extra serious cred there, Adrian. I have a few subtle nods to MCM in a few of my recent videos too. Keep up the great work, I am a big fan of your channel also.

[@BrassicGamer]

I appreciated the explanation of VA vs Watts, thank you.

[@retropuffer2986]

Good to see the II+ in all it's 80 column glory!

[@JanPaulini]

Very good explanation of W vs VA ! Like your videos, thanks for the great content.

[@clough99]

great explanation on the VA and watts relationship

[@senilyDeluxe]

Another big benefit of an isolation transformer is that you can measure antique TVs or radios with your oscilloscope without blowing up either of them. Or hack an AV input into an ancient TV (by ancient I mean older than say 1980) - found out the hard way. Had a TV from '78 that was hot chassis, I didn't know about hot/cold chassis back then, it had a nice silk screen showing the trace that had the video signal, so I cut it and hooked a monitor (which had an isolation transformer) to it and to my delight it displayed the picture the TV was receiving. So I hooked up a VCR to the other end, the VCR was hooked up to the cable, the cable was hooked up to Ground and the TV went BOOOOOM! Although an isolation transformer would be overkill. A small HF transformer for the signal itself would do - or like Tandy RadioShack did it - an optocoupler.

[@londongaz2]

Glad I'm not the only one that breaks stuff (10:01) ... I left my little YM2149 project on the side and my cat sat on it.

[@More_Row]

Neat stuff Adrian, thanks for the awesome videos .

[@electronicengineer]

Thank you for all of your continuing efforts and all of the work you put into making these great videos for us Adrian. I love that you always try to use all of the items that your viewers send to you in the upcoming videos. Such a genuine approach to making your videos, by a very genuine guy. I really enjoy the "Mid-week mail call" videos a lot! Thanks again Adrian! Fred

[@briangoldberg4439]

About the isolation transformer. I think it's also worth mentioning that North America has the neutral line referenced to ground on the mains. What that means is that you cannot use test equipment (like an oscilloscope) on a DUT when the ground (of the DUT) is referenced to neutral internally. Most CRTs are like this, and if you try to plug your scope probe ground up to the set, you will either trip a breaker or blow up something.

[@EngineeringVignettes]

I use an isolation transformer along with an auto-transformer and a dim-bulb setup. It's a good bit of kit. You probably don't need the auto-transformer, but you might want to add a switchable dim-bulb, for cases in which you are plugging in and turning on devices of unknown history and you don't have a lot of spare fuses lying around. Cheers,

[@GigaLem]

catching up on videos I missed during the editing process of my lemmings Let's play. A package from my state? what a lovely surprise! I do hope I find a space for older computers because I still find old 90s computers interesting to this day.

[@UpLateGeek]

Thanks, that was a great description of the whole watts/VA thing, and how an isolation transformer protects you. I think I need to go buy one now!

[@peterg.8245]

VA is not just the product of Volts and Amps it’s a complex conjugate of real power and reactive power. Things I learned in my BSEE but never used professionally because I became an Instrumentation and Controls Engineer for petrochemical combustion. We don’t call them explosions we call them rapid combustion events.

[@Cherijo78]

I remember having this in my apple ii+ as a kid. I even remember the way the 80 column mode annoyingly went below the horizon just like yours did lol. It later got swapped out for a laser 128 with a sidecar for expansions, and the laser 128 just had a switch about the keyboard for toggling.

[@merykjenkins3274]

Isolation transformers are great for testing equipment that potentially has faults that would normally trip the ELCB and let you diagnose those faults without it tripping all the time. They can be dangerous as if you shock yourself, they will keep shocking you as there is no ELCB detection. I always used to fit ELCB/RCD outlets to the Isolation tx's that we used at work to protect the people using them. Not good for testing 'leaky' equipment (such as minor earth faults from degraded insulation or shorts) but will stop people getting electrocuted from faulty gear or sticking a fork into a toaster hooked up to the Isolation tx. IMO, Isolation transformers are a useful tool but are much less safe for general use. Maybe a good mod that you could show is fitting an RCD or ELCB outlet to the iso tx. Thanks Adrian for the great content!

[@ulflulfl9464]

Well, there is no point in putting an RCD behind an isolation transformer for raised personal protection - it just won't help. In the normal mains circuit, the RCD detects differential current between phase (L1) and neutral (N), which should sum up to 0 - that's the case unless there is a faulty current flow through protective earth (PE) or "the earth". However, when using an iolation transformer, there is no connection to (protective) earth, as that's the main point of it. As there is no connection to earth, there cannot be a current that the RCD can detect. This is the way the transformer can protect you: You can touch one wire without electrocute you, as there is no way back for the current - the circuit is not connected to the earth you are standing on. The RCD is not needed. If you connect the output circuit of the transformer to earth, e.g. when using an oszilloscope connected to earth, the RCD won't help in protection either. If you touch the wrong wire in that case, there might be a current from your finger, over the ground you're standing on through the oszilloscope back into the transformer circuit that can kill you. But the RCD won't "see" this, as there is still no differential current between L1 and N at the transformer. Hopefully this is a bit understandable without a drawing. Bottom line: Don't play around with mains voltage (even with an isolation transformer), unless you know what you're doing ...

[@merykjenkins3274]

We tied 'neutral ' and earth together (NE bond) which gave a reference for the rcd to work. Working in our particular environment this was necessary. When dealing with old and potentially faulty equipment, especially power supplies or stuff with metal chassis, if you have a 'neutral' insulation fault to the chassis and you have one hand touching that, and the other touches the 'active' you will get shocked. An earthed chassis makes this scenario impossible as it creates an imbalance that trips the elcb. If its live to earth, it pops the breaker as soon as switched on. In an isolation tx with a live chassis, you will need to blow the breaker at max amps before you stop getting shocked. Thats a lot of amps for a 300va iso tx, where death can be as low as 30mA. Yes, you can run equipment with faults, like I said, great for fault finding if you are very careful, and yes you can (negating capacitive bonding) theoretically grab a live conductor and not get shocked, but if you do get shocked, there is no protection from becoming a crispy critter. This is almost made worse by the iso tx. Consider a chassis with a direct 'neutral' fault. You stick one hand on that to hold it steady. No problems because no earth path to get shocked. You have no idea that if you then accidentally touch the 'active' then its game over.

[@ulflulfl9464]

@@merykjenkins3274 If you are working with both hands on a potentially (isolation) faulty device under mains voltage you already made at least one mistake, regardless of using an isolation transformer or not. When I get you correct, you are using an RCD after the isolation transformer and connecting N and PE between the transformer and the RCD. In the special case that you have an isolation fault of N to PE at a device and touching with two hands at the wrong places the RCD may trip (remark: but it also may not trip if the isolation fault is massive). So you may (or depending on the device fault may not) be protected in a specific case and under specific circumstances. However, in many, many other cases you are still not protected by the RCD. In my opinion using an RCD here will give the "uneducated" a false sense of safety: "There is an RCD installed, so nothing can happen". That's the same wrong understanding as: "There is an isolation transformer installed, so nothing can happen". As I already said, don't play around with mains voltage (even with an isolation transformer), unless you know what you're doing ...

[@merykjenkins3274]

Well, you do you, ill do me. I would never use an isolation transformer in my house or workshop as they remove the elcb and rcd protection. I can safely stick a fork in a toaster, drop a hair-dryer in a bathtub, grab a live wire or any other stupid thing (not that I would), and all I will end up having to do is either reset the breaker or elcb. Its all about context. Communication and computer people use iso tx's to remove or reduce transients, as they do in hospitals. Technicians, like me, use them to power faulty equipment to diagnose faults while they are live. Being educated in diagnosing faults on high power three phase equipment, I would always prefer to do this with the supply isolated, if not, a iso tx can be a useful tool to stop the rcd or elcb activating. But it should not give someone the idea that they are safe. As described above, it introduces a highly likely scenario brought on by a false sense of security where you may get shocked and draw the full rated output before the system will sense a fault and shut down.

[@ulflulfl9464]

@@merykjenkins3274 Seems we had a similiar kind of education :-)

[@DavidWonn]

I can’t imagine how awesome it would’ve been to have dual monitors on the Apple ][e back in the day, especially a green screen for 80 column mode and a color monitor for 40 column / graphics modes. We were lucky just to have 80 column support via the PR#3 command on a green screen when my dad bought an Apple ][e as his first home computer.

[@AnonymousRepair]

KZbin is great platform for learning

[@allenhalk4203]

I hope you see this!!! Make sure that the earth/ground on the secondary side of your transformer is also isolated. If it is not you are still referenced to earth/ground/neutral at your breaker panel. Stay safe love your channel

[@jaycee1980]

It wouldnt be sold as an isolating transformer if the secondary side was also ground referenced

[@allenhalk4203]

@@jaycee1980 that's not necessarily true. I have been looking into getting a isolation transformer and have become aware that the earth/ground seems to non-isolated quite often. I wouldn't bet my life on not testing it. www.eevblog.com/forum/beginners/dangerous-troubleshooting/

[@jaycee1980]

@@allenhalk4203 It depends what youre talking about. If you mean the safety ground connection (the top pin) then this is indeed wired straight through, and should be. What should NOT be wired to ground is either the live/hot or the neutral/cold terminals of the outlet.

[@allenhalk4203]

@@jaycee1980 if the earth/ground on the device your working on is connected to the earth/ground of the outlet that is bonded to the neutral in the breaker panel you are not isolated from the panel and that is dangerous and gives a false sense of security it can also blow up your oscilloscope or other test equipment kzbin.info/www/bejne/jnPWgmapj5lofM0

[@jaycee1980]

@@allenhalk4203 safety ground is not the same as neutral - why are you assuming it is ? Unless your equipment is WRONGLY connecting neutral and safety ground, there is no problem

[@maxtornogood]

15:58 - Not just Australia but *SOUTH AUSTRALIA?*. Nice, I live in South Australia too!

[@Dreamsarefragile]

This was such a great video, you mention Mighty Car Mods and dave from EEV Blog, but no Bigclive! he's the power factor of with the hoppy meter. keep up the good work love your videos I learn lots.

[@tubeDude48]

At 25:28, that's a Pinned IC Socket. At 32:00 make sure the ground lead ISN'T tied together! It would be a good idea to rip-off the ground on the primary side. I know, I know someone won't agree, but that's your choice. With it connected, it caused a ground loop!

[@bobblum5973]

Re: 32:00 ground lead, are you saying to make sure the grounds of the primary and secondary are not tied together? If so, I tend to agree, but every isolation transformer that I've ever used does not connect the secondary outlet ground to anything at all, and states it on the label. Ķind of like the AC outlets on DC-to-AC power inverters. Well, at least the _good_ isolation transformers and inverters do! 😉

[@tubeDude48]

@@bobblum5973 - Yes, I agree. But I have had 2 Isolators that were linked from one to the other. :)

[@bobblum5973]

@@tubeDude48 I'm not too surprised, your experience may be a lot more recent than mine! I haven't had to work with much newer gear. For example, I've bought a few super cheap DMMs from Harbor Freight as "I don't care if I lose them" but was still surprised at how much they cut corners when I look inside. They work okay, but for how long? For real work I use a couple of older more reliable meters. Safety on the test bench is not the place to cut corners.

[@cappaculla]

Adrian, when I thought I you couldn't become any cooler, turns out you are also a Mighty Car Mods fan.

[@PatrickAustin]

Fully agreed!

[@Walczyk]

i read this like dumb and dumber, such a good movie

[@mikeuk666]

keep up the great work Adrian 🕹 ♥

[@godzero1970]

That little screen in the background Rick Rolled me at 4:16.

[@frankowalker4662]

Great MMMC, as usual. Nice isolation transformer.

[@nilz23]

Power factor of less than 1 is when a reactive load causes the current to lead or lag (out of phase) the voltage. A reactive load can actually send stored power from the device back to the grid. Edit: your explanation of why a switching supply has a lower power factor is correct though, however I doubt that boat anchor monitor has a switching supply in it! Also I use realCalc just about every day, it's one of the few Android apps I got the paid version of.

[@pastedtomato]

Australian viewer called Craig.... Now that's a name I can trust.

[@nilswegner2881]

Fellow DankPods fan?

[@pastedtomato]

@@nilswegner2881 Perhaps

[@nilswegner2881]

@@pastedtomato i love that guy, escpecially his little adlibs like na-no or aww my pkcell

[@xantam23]

Thumbs Up for the Interpol Shirt in the Intro. 👍🏻

[@dosman01302]

That's cool to know your into cars too. I do love the videos. Keep up the good work!

[@capitanschetttino8745]

Thank you! Your very clear explanation solved this mistery (about watts, ams, pf) for me! cool!

[@drruncmd]

I like to use toroiadal transformers as a preference because they have an added benefit. They typically are used for audio applications for cleaner AC but also, they have a thermal cut out internally to prevent overheating or overloading over a period of time. Fantastic explanation tho. I didnt really understand VA at all until now. Thanks Adrian.

[@BertGrink]

Doesn't toroidals also have better transfer characteristics than transformers with rectangular cores? Meaning less loss of magnetic flux in the core.

[@drruncmd]

@@BertGrink Yeah this is also why the toroidal transformers are used in audio power amplifier equipment. Smaller E shape transformers were used in smaller audio equipment such as boomboxes and tape players.

[@drruncmd]

@@BertGrink Toroidal transformers are not really used for 1 to 1 mains isolation, but variacs are toroidal and provide an adjustable output.

[@drruncmd]

@@BertGrink I think also another benefit of toroidal transformers are that they have a different form factor so can be easier when designing equipment cases and enclosers to incorporate their size and space. But, they are as heavy as standard transformers.

[@BertGrink]

@@drruncmd Toroidals would also be easier to keep reasonably cool under heavy load due to the hole in the middle; you could easily place a fan on one side (or both, even) to have a steady airflow through and around the transformer. The biggest downside to this type of transformer seems to be cost due to the more complex machines required to manufacture them.

[@antagonizt]

Nice Interpol t-shirt!

[@jNetDowling]

Haha, I came here to say the same thing

[@twocvbloke]

The only isolating transformer I have is a step-down transformer I was given some years back, 240v in, 120(ish)v out, must have been made in the 50s or 60s as it came with some rather vintage (and broken) British-made bakelite US sockets, which I replaced with modern ones sourced from the US back when the USPS didn't ream its' international customers for all the cash they could, as well as a very old and degrading old-colours mains cable (back when the UK used Red for Live, Black for Neutral and Green for Earth, when such things made sense), has been useful to test things with universal voltage switching PSUs, aswell as eliminate audio noise on some things to find where it was coming from too... :)

[@Dukefazon]

Talking about sweets, these are a couple of desserts made my Kinder that are stored in the fridge in the stores so they can't send you them. If you happen to wander into a general store during one of your European visit check out the parts where they keep yoghurt, butter, etc, you might find some sweet and tasty treats there! Also, if you visit Hungary, check out Túró Rudi if you like cottage cheese, it's a roll of sweet cottage cheese in chocolate coating, we really like it here (also needs to be kept in cold).

[@organiccold]

Adrian, nice video. Thanks i love your channel. Regarding the transformer i have a friend that has a company specialized in rewinding transformers, motors and etc and those transformers have a inbuilt fuse in the winding, so if it blows needs to be opened and replaced, normally this means rewinding it again. :)

[@serratedwarstep]

Adrian, my name is Joel and I'm a Unix/Linux Systems Administrator living in North Carolina (just an hour or so drive from LGR) I just wanted to say that I really appreciate your content, your contributions and your enthusiasm for your viewers and the content you produce. I watch your content to unwind from a long day at work and I truly thank you for providing that for me. You're an awesome guy!

[@richardbrobeck2384]

Adrian I had that Color monitor for my Apple 2C

[@dreamvisionary]

That brush is identical to the one that I use with IPA for cleaning flux off of PCBs. Thought it's intended use is for cleaning dentures, so perhaps he thinks your have those 😂

[@GarthBeagle]

Great explanation of VA vs watts

[@danmacdonald5166]

Your explainations were good. The only time i saw VA and PF was on a 60KW or 48VA generator or vice versa

[@dieSpinnt]

Thanks Adrian. And also for the video:))) You got it right. Watt as the equivalent heat output is completely sufficient. No reason to invent the flux compensator:) - to heat one gram of water per minute by approx. 14.3 Kelvin, or - to maintain an electrical voltage of one volt via a purely ohmic resistance of one ohm (whereby a current of one ampere flows; 1 W = 1 V ⋅ A). And now to something completely different: Your "Adrian CAD" is absolutely fine. It was a wise decision to choose three full waves as the visualization. The KZbin algorithm would otherwise identify nipples. Well, just kidding :) Future Jed: At 40:12 ... Maybe I should think again about my impressions:P Also: Who would produce "spikes" on purpose? Speaking of it: Translate the (absolutely legit) zero switching point, where sine-waves have the less steep tangents in the middle of the sine-wave, what also translates to: The worst design decision you can make. Yeah its just an example drawing, but that is what it says in fact:) Explanation: Unnecessary high currents, what a real device has to address with components that otherwise could be at lower specs ... and therefor: lower price. Hmmm, no I am totally wrong. Adrian never says that this is a design. So i revoke my judgment to: "Not like reality" ... what is absolutely legit for explaining the basics of electronic.

[@justovision]

The ground connection on those are often connected straight through so you need to use a non-grounded adapter to actually get isolation.

[@FireballXL55]

The isolation transformer is not used to isolate from ground, it is purely to isolate from the mains supply from ground, which usually the neutral is grounded somewhere in the system. This enables you to connect your scope ground to either the +ve or -Ve of the main primary side smoothing cap without blowing a fuse or tripping a GFI. But if the UUT has a fault which grounds one side of the isolated supply it is no longer isolated from ground this includes the scope ground lead..

[@dieSpinnt]

@@FireballXL55 Very nice: Cutting the yellow/green is exactly the same (To say it in other words: DON'T DO THAT). Unless you do primary side measurements of the PSU, what do you think the PSU is? Exactly, an isolation transformer. The CASE is grounded. That is not done as a joke. It is for your security ... as the oscilloscope enclosure is. Isolation transformers are used to mitigate the possibility of the osci shorting to a mains phase ... WITH THE OSCILLOSCOPE. It won't protect you from CRT High voltages, that are already isolated and have no common potential with mains earth. So: WHO IN THE WORLD WOULD PUT AN ISOLATION TRANSFORMER BEFORE A DUT(Device under test) THAT IS MAINS EARTHED??? Just think about it: mains -> some sort of PSU ... what is in fact an isolation transformer -> low voltage supply lines. ROTFL, double isolation transformation ... a joke (unless you are doing primary side PSU measurements)? No, that is just like cutting the mains-earth line. The isolation transformer belongs to the oscilloscope. RTFM! To mitigate shorts because the oscilloscope is a mains-earthed device, too. That is a security essential feature and if you remove that, you have to be sure of what you are doing!!! CRT's: Neither an isolation transformer nor a resistor will make that thing safe to operate without a case. Even without any power applied, the CRT can develop a lethal charge within it. Even with isolation, there is still a huge voltage produced and you can still come in contact with it. "no longer isolated from ground this includes the scope ground lead" ... That is why someone with education would use the isolation transformer at the device where it belongs to in the first place. At all this thread is missing something important: A thick uppercase message, not to do that. There are other possibilities: Differential Probes, All(nah, most) service technician handheld oscilloscopes are protective insulated (class 2), insulating protective mats, insulating safety shoes ... all not important for checking out a CRC, there is no (mostly no good...) reason to use an oscilloscope to display static high voltage signals. P.S.: If you think that electrical shock is the only problem then watch out: A short circuit caused by a direct earth fault such as incorrect handling of an oscilloscope can have terrible consequences. Metal sublimates in microseconds and is deposited as a fine film on the face and when inhaled in the lungs. This is even worse if the device protection fuses were bypassed as a result of improper handling and the circuit breaker, e.g. from the house installation, comes into play. CORRECT measuring stations have isolating transformers WITH their own protection of the devices, up to and including temporarily grounded residual current circuit breakers explicitly for the measuring station. Please excuse me again to stress that. But this is about vital safety!

[@FireballXL55]

@@dieSpinnt I think you misunderstood me because your reply does not make sense. Switched mode PSU with bridge rectifier on the input, the -ve terminal of the bridge rectifier is not at chassis GND so you can not connect a scope GND lead to it unless you connect the PSY via an isolation transformer, or you are naughty and disconnect the scope earth connection in the mains plug, something you should NOT do. I have been using an isolation transformer for 40 years to repair switch mode PSU's and live chassis TV's. I remember trying to explain to a graduate why it is the equipment you are working on and not the scope that has to be connected via the isolation transformer.

[@FireballXL55]

@@dieSpinnt No the chassis is not isolated with an isolation transformer, so it is not the same at all.

[@dieSpinnt]

​@@FireballXL55 Don't fight with me about something you can easily measure yourself. I am not your safety advisor, too. RTFM! It is easy as: There is ONE Potential(Voltage like) to miss. You say that you are repairing PSU over 40 years? Is your advice to generalize and that there is only one fucking type of ... let us call it the RICHARD-type? I surely must have misunderstood you. EARTHING IS SUCH A MISTERY For fucks sake, it is YOUR security insurance. You are reparing a transformer for 40 years without knowing that you repair a transformer ? You are the worst troll ever. ROTFL

[@douro20]

Micron must have had a lot of process problems back then. My isolation transformer came out of a piece of medical equipment a friend was parting out. I think it's the same size or slightly smaller. It also didn't have a lot of use since the equipment it came out of was a prototype.

[@JacGoudsmit]

Power factors that are lower than 1.0 are basically caused by capacitors or coils that change the phase of the current compared to the phase of the voltage. Usually when something like a power supply would have too bad of a power factor because of the transformer coil, regulations require that the manufacturer also put a capacitor in to compensate.

The isolation transformer explanation reminds my AC Circuits class, but this time is clearer 😅

[@kins749]

Very interesting, I always thought VA and W were the same thing.

[@alerey4363]

Only for 100% resistive loads; for any other real world electronics (made up of inductors and capacitors) the power factor varies between 0 and 1, thus your Apparent Power (the one measured in VA) is the resultant of Active Power (Watts) plus Reactive Power (VAr, Volt Ampere Reactive); they are NOT the linear sum because they are all vectors spinning in time at the given frequency (60 Hz in US, 50 Hz in Europe/SouthAmerica)

[@TheRedneckExpress]

Aye, this helped clarify a few things as I work with inverters a lot and it helps better clarify why they have "surge wattage" ratings for them to handle the spikes you can see on things like induction motors during their initial starts.

[@Natures_Intentions]

The apple 2 + is the first computer I used. Very cool computer

[@Renville80]

With transformers, it’s all about the turns ratio of the windings. Using Adrian’s example of the 9 VAC transformer, the ratio would be 13 1/3 : 1. So for every turn in the 9 VAC secondary, there are 13 1/3 turns in the primary. An isolation transformer therefore has a 1:1 ratio. Also, there are three quantities when dealing with AC power, and they can be illustrated by a right triangle. Watts is the base of the triangle, kVAr (reactive power) is the vertical side of the triangle, and the hypotenuse (longest side of the triangle) is kVA. Without getting too technical, reactive power is that energy required to create the magnetic field in a motor, transformer, or inductor. Power factor is another number that comes into play with these quantities, and is more than I can put in a comment...

[@titactaco]

Best explanation of PF and VA I've ever seen on youtube. Good stuff, dude.

[@dexteria3467]

me to I loved the mighty car mods .. and really like to have also the chopped sticker :D

[@kd5byb]

They say when you get old, your memory is the second thing to go. I don't remember what the first one was! baa haa haa, I'll show myself out... ;)

[@Dorff_Meister]

RPN Represent! I'd love to fix my old HP 42s (battery corrosion related, I'm sure) but it's in the closet until I do.

[@aaronbrandenburg2441]

Hey out there this may very well be kind of redundant comment but didn't see anything in regards to this. Glancing through comments but is important to realize this anyways even if it is redundant! Not all Transformers are isolating type of Transformers or even isolated at all. One good example is the autotransformer. In which the primary winding is in one form or another connected electrically to the secondary. Such as in some step up Transformers for example of running european-made equipment on us 120 volts! A lot of those are on auto Transformer which provides no isolation. Although there are isolated ones available but it brings the costs up considerably since an autotransformer does not require as much copper and is much simpler! Auto Transformers are frequently used for various purposes and just to be aware of the fact that they are not isolating is the main thing. Also there is a big difference in two different types of isolation Transformers. You have your so-called technical grade isolation Transformers which are completely isolated from the primary and secondary. Some of the so-called medical-grade isolation Transformers are more for electrical noise then life-safety. They are wired differently but if you wind up with one of those they can be converted to the actual time that you would use a technical grade isolation Transformer with a few wiring changes! It's something to look out for when purchasing and isolation Transformer! The structure sister expensive and you'll probably be getting one used more than likely. If you have a beefy power supply Transformer to nearly identical Transformers although it'll be a little bit off since nothing's always spot-on identical. Two low voltage Transformers of sufficient current can be placed back to back low voltage secondary to low voltage secondary. To provide isolation but I would not recommend this but it is a fairly common practice occasionally not universally but here in there this is use. I've seen plenty of times and Equipment there would be two low voltage Transformers back-to-back acting as an isolation Transformer especially in older equipment. And Austin that would be worth looking into would be something it's known to contain and isolation Transformer and salvaging non-working equipment for that and possibly other goodies. I know all too well about non isolated power. Built a battery charger years ago on the cheap that did not even have a Transformer! Essentially a lightbulb full Bridge rectifier and other components equals battery charger. Not something you would really want to do but at the time it did what it needs to do.

[@MichaelNiculae]

I have the chopped sticker on my car too! Shoutout to Moog and Marty, woo

[@chaseohara4781]

That brush is for dentures! They have them in North America too.

[@markmooney4770]

Your power factor is dependent on the TYPE of load you have. A switching power supply is one example, but another would be using an inductive load like a large electric motor. It would have a power factor less than one. That's why they use high voltage capacitors for power factor correction in industrial sites where larger electric motors are used.

[@wolvenar]

As usual thanks for the entertainment and information.

[@rfmerrill]

The SMT breakout you showed is more likely for use with a solderless breadboard or perfboard. Using it in a chip socket would only make sense if there happened to be an SMT chip with the same pinout as a DIP chip that you can't get anymore--which is a reasonable thing to encounter, but I don't think it's what the breakout/adapter mostly sells for. Although I suppose you could intentionally design it into a board so that you can socket an SMT chip

[@robertwielewicki1249]

Great vid as always

[@RudysRetroIntel]

Great video!! Is there a link for the 80 column board and ICs? I don't see it on the notes

[@aaronbrandenburg2441]

I'm sorry I can't do that Dave!

[@stargazersfield]

Perhaps I have missed it in your video catalog, but do your have a video that talks about various EPROMs and burning our own, such as the Apple L/C ROM, etc? Thanks for the great channel.

[@-GrimEngineer-1337]

The secondary side of the transformer is a separately derived source. The neutral conductor of the secondary side should be ground referenced per NEC. If you want watts you need to compute VA and multiply by your power factor. Power factor is the cosine of the delta in degrees between volts and amps, leading (capacitive) or lagging (inductive). True power versus reactive power is determined by the area below the sine curves of the voltage and amperage. .4 is a horrible power factor for a loaded supply! PF is hard to measure at low loads because there is almost no data for the amperage curve, and very often looks bad when unloaded.

[@TheEmbeddedHobbyist]

The whole point of not grounding the secondary side is to remove the mains reference to earth with a isolating transformer. this allows you to be safe if you touch either side if the secondary and earth without killing yourself. if you connect the secondary to earth you will be defeating the point of the transformer.

[@sarreqteryx]

20:04 it's a denture brush. I guess you could use it for cleaning PCBs.

[@sonorafx]

Congrats Adrian! which calculator app are you using?

[@thedopplereffect00]

What happens to the ground of the isolation transformer? Does this end up bypassing the safety mechanism of your GFCI?

[@FireballXL55]

if you connect yourself across the secondary winding you will get a 120V electric shock but because it is isolated from ground then the GFI will not work.

[@jaycee1980]

There is no ground side, there is only the two ends of the secondary. Neither are ground referenced - which is why it's called an isolating transformer. If you touch a live conductor straight out of your wall socket, the current finds a path through you down to ground - literally the ground you are standing on, because the power coming into your house is referenced to ground. The distribution transformers actually have a connection from their center tap straight into the earth through a huge grounding plate. With the isolation transformer, if you touch only one end of the secondary winding, no current can flow, because no circuit is formed. Sure, if you touch BOTH ends of the windings, then you get a shock.... but touching only one end means your body may be connected to a voltage of 120V, but there is no current flow - it is current flow that electrocutes you. Same reason the birds can sit on the power wires and not get electrocuted. The GFCI (RCD's where I come from) doesnt work because it's only detecting current leakage to ground that does not go back through the cold/neutral wire. If you were touching both ends of the isolation transformer's secondary, the current would flow through the winding, and there's no leakage to ground, so it wouldn't trip.

[@ncot_tech]

If you use an isolation transformer and accidentally do touch both isolated outputs, it wouldn't trip any breakers would it? So shouldn't an isolation transformer have its own breaker on the output?

[@kaitlyn__L]

Other commenters say it’s specifically useful for testing equipment with shorting faults without repeatedly tripping stuff.

[@ulflulfl9464]

There are usually two kinds of breakers: An RCD for people protection and an overcurrent protection against line and device destruction / fire hazard. In the response to Meryk Jenkins comment above, I've pointed out why an RCD has no use at all here. A suitable overcurrent protection (aka: fuse) would be a good idea, as the normal mains fuses (e.g. usually 16 A in germany) are much too "big" to protect the transformer and the circuit behind it well. Having a matching slow fuse (300VA / 120 V -> ~3-4 A) would be a good idea. However, the transformer already might internally have a thermo fuse which serves the same purpose ...

[@kaitlyn__L]

@@ulflulfl9464 I don’t see anything by a Meryk Jenkins, how odd

[@idio-syncrasy]

Brilliant.

[@NivagSwerdna]

I just bought a 240/110V isolation transformer... it's only 100VA.... but looks like I should get away with it. Thanks for the PF stuff... I hadn't considered that!

[@NivagSwerdna]

A supplementary query that comes up is... should you plug your oscilloscope into the isolation transformer or use a regular socket...

[@eDoc2020]

@@NivagSwerdna Just plug it directly into the wall. An oscilloscope's power supply is already isolated. However you need to remember that an oscilloscope's ground clip is connected to chassis ground, so if you probe mains equipment without the isolation transformer you will cause short circuits.

[@dieSpinnt]

To the Power Factor: It is often portrayed as a bad thing to have one besides of one. Good public relations work! Remember who it's bad for ... For the energy companies;) ... but yeah, in the end, for all of us. We all pay the difference. That is the market.

[@Hidyman]

What kind of cars are you into?

[@TechTimeWithEric]

I was going to mention that is a denture brush. They are sold in the standard toothbrush isle. But do you think you might be able to do a video on your car and truck and talk about any mods, if any that you have done?

[@philiplord2818]

Adrian, how would I be able to get my hands on a couple of these replica Videx Soft Switches...Would love to talk to Lee

[@philiplord2818]

Hi Adrian, I've done a bunch of searching, but still can't seem to track down who produces these softswitch replicas. Would love to talk to Lee. Hope you can help. Cheers

[@opp31337]

2020 was a leap year so if my 3:18AM brain is correct, it was exactly 1 year since you repaired the c64 that you did the modern 8701 chip. or would it be a year and 2 days?

[@twobob]

explanation was fine

[@rothn2]

I would love to hear more about these isolation transformers. My intuition is that if you touch a wire with a high concentration of free electrons and something conductive with a low concentration of them or vice versa, current will flow and you will be shocked until some sort of equilibrium is reached, regardless of isolation in the source. How does electrical isolation change this situation?

[@jeffhurtson5211]

This video explains it pretty well. If you have any questions after watching it you can ask me. kzbin.info/www/bejne/pH6roZJ6e7iYnZI

[@rothn2]

@@jeffhurtson5211 Thanks! I think I might get it now!