Power Supply Knowledge - Tech Talk At The Lab!

hi everyone and welcome to another episode of mr carlson's lab let's get started hi everyone welcome to another tech talk episode so in the previous video i asked what you would like to see whether you wanted to see that bizarre looking scope or this and it was almost a tie lots of people interested in both so let's take a look at this power supply and then of course in the future we'll take a look at that scope with that weird looking crt that sticks out of the front of it so what are we going to do in this episode well i'm going to take this thing apart and i'll explain exactly how this power supply works so i'll share some power supply knowledge with you now here's the thing with this power supply to start you're the regulator so this doesn't have any regulation ics in it or anything like that who needs an lm723 or ua723 or tl494 or whatever you don't need that because you're the regulator what's better than that so anyways grab your favorite beverage i've got mine right here let's open this thing up talk about it we'll take a look at the schematic and i'll explain exactly how this device works all right let's open this thing up so it's quite a heavy power supply lots and lots of weight to it oh and by the way if you didn't watch the previous video so this one here goes it has a zero to six volt scale and a zero to 12 volt scale but since it's not regulated of course there's a lot of overshoot they're taking into account that this is going to be loaded and i'll show you that here in just a moment so it's rated at 10 amps at 12 volts and at 6 volts it's rated at 20 amps so you have the amp meter right here and then we have the volt meter right here and of course again you are the regulator so let's open this thing up and take a look at what's inside you can kind of see what's inside already so remove these two screws i think these are the only two screws again you're looking inside this thing the same time i am i haven't opened this thing so i've had it around for a while i'm gonna make it but i haven't done anything with it because i want to save this kind of stuff so that we can experience this together oh crust so notice my coffee is out of the way so that is a very important thing to do so you can see we got two diodes here and another two diodes here looks like it's been a little bit warm so as we move this along here this is selecting different taps on this transformer somewhat like a variac oh look at this scary workmanship here eh look at that somebody's added some extra capacitance oh there is some scary workmanship in here so i think this is going to need a restoration as well so we'll do that down the road as well so i've got the two capacitors tacked in here on this one and we have another one over here so somebody's really been um somebody's really been adding capacitors to this thing probably trying to get rid of that hum for a um for some very delicate use maybe who knows wow yeah that is looking pretty scary so this is a plastic body and this is taped up against it so it should be okay we'll power this thing up i'll put this on my current limited isolation transformer and variac supply and uh plug the thing in so it looks like what they've done is they've paralleled some capacitors so these two here are in parallel across this terminal here and then it looks like they've paralleled this one in across this one right here so they've added a bunch of extra capacitance so this could be replaced with some nice small capacitors now so 5000 microfarad see that right there 5000 micro farad 20 volts just move this in nice scary stuff i always like finding this stuff it's exciting when you've done this for long enough you know some people get horrified by this i kind of get excited by this i go wow this will be a fun restoration and we can do this together maybe that's why i get excited because we can experience restoring this thing together so yeah you know in the grand scheme of things this is pretty horrific like look at this workmanship right black tape capacitor in parallel when capacitors fail or get weak you know the biggest no-no of all is putting another capacitor in parallel with it because a lot of the times the capacitors go open and then for no reason they go closed which means they short so basically what this guy whoever is doing this whoever did this is using this capacitor as a binding post most likely so they're just using this as you know binding posts for extra capacitors so what did he add in so this is 2000 and i imagine this is the same probably it is 2 000 micro farad so he added in another 4 000 micro farad parallel capacity capacitance so it it looks like it would be open right you know we're down 1 000 microfarad from this one and this is all covered up by tape so i'll save that for the uh i'll save that for the restoration we'll uncover the uh the glory of this wonderful power supply at that point i have the power supply attached to my isolation transformer current limited variac supply the control is down at zero as you can see and that's where it should always be started when you're using a power supply like this i have this set to the six volt 20 amp position and i'm about to turn the switch on so what do you think is going to happen let's find out this is always the fun part oh the indicator is glowing nice little neon lamp in there so if i turn this up i should see dc voltage but i should see no current because there's nothing across the actual binding posts here so if this moves up then there's something wrong inside here as well let's see what happens that's looking good there's the six volts so six volts 20 amps but wait a minute i can turn this right up to 13 volts and it says 6 volts 20 amps is that normal absolutely it's normal because you're the regulator there is no load on this thing so there's nothing loading this thing down right now so this is just you know free floating there's just the transformers not not loaded so if i add a load i have this resistor these two resistors paralleled here i just recently did a power supply demonstration on patreon and this is already together so i can just grab this for this so what i'll do is i'll add a load so if i add a load to this this should drop down and i should see current draw so let's see what happens look at that and wait 10 seconds for the thing to settle down bouncy needle look at that eh so and if i let go comes back up again no problems and those resistors are getting mighty toasty so that happened just in time these are very hot at this moment very hard so there you have it so that's working that's absolutely normal so if i turn this down look at that capacitors are working very well too because right now this should just fall to zero right if there was no caps in here if the caps were bad this would just drop right down to nothing so i'll grab these very hot resistors here again whoa those are hot holding by the corners here drain that capacitor off and there are the capacitors and as you can see no problems so let's go to the 12 volt 10 amp setting so where do you think this is going to settle off if i turn this to max where do you think the needle's going to go let's see that's 12 volts there right well somewhere way over 20 volts again that's absolutely normal because you are the regulator you are the analog regulator so you're probably saying to yourself right now this is a scary power supply why would i want to attach this thing to anything i own well this is a very useful power supply sometimes known as a brute force type of power supply they have very few components in them basically diodes capacitors and you know a bunch of meters and a transformer in this case a little fancier it has that variable transformer in there as well but very dependable power supplies and very rarely fail now as you can see in the in this thing they've replaced the capacitors or bridged some in for some reason if maybe the factory capacitance they wanted to add more or maybe the factory capacitor is bad we'll find that out when we restore this but capacitors are a common item that fails in pretty much everything especially something this age right so replacing those capacitors this thing could probably go forever again no problems so turn this thing down and i'll use these resistors have they cooled off enough for me to handle properly yeah they're not bad so i'll just drain the cap off here so this is at zero and there we go bring the caps capacitors off right there so no problems it's working very well oh we didn't take a look at the current here let's see what happens if i put this across this boy these are going to get hot right now so i'll just tap this on here real quickly and let's see what kind of current draw we get yep that's working good no problems whoa those are hot they smell i can actually smell these just a boat could smell my fingers there too as well whoa that's getting hot that burned me really quick i bet you the wire in those wire wound resistors was glowing orange and then it just takes a few moments for the heat to transfer to the ceramic case so at this point right now these things are incredibly hot is incredible you don't probably almost see the heat waves off this thing crazy anyways it's working well so what would you use a power supply like this for well you could use it for power and incandescent lamps for testing lamps you could use it for powering dc motors you could use this for testing old car radio 6 and 12 volt vacuum tube car radios no problems you could use it for charging batteries again you are the regulator as long as you're on top of this no problems so how would something like this work in a case like that how would you set something like this up well you remember i said you always need to start off at zero okay so say we had a six volt car radio we have this in the six volt 20 amp position all right i'll grab these resistors here again because they're very hot and i'll just drain that cap off in there so i can get that in there there we go drain the cap off so it's going to read correctly okay so you would have your six volt car radio sitting off to the side say this is the car radio and you've got the wires running up to the binding post here all you do is you make sure this is at zero always start at zero the radio is on so the switch on the radio is on at this point turn this thing on and you would bring this up to six volts like so now the tubes would be lighting up on the radio but the radio isn't fully drawn current because the tubes in the vacuum tube radio aren't into a mission usually the vacuum tube radios they take about 15 seconds or so to come into a mission when the vacuum tubes in the car radio warm up they're going to start to have emissions so they're going to draw current from the high voltage supply so what you're going to see is this is going to drop back again and this is going to draw even more current so say you're starting out at say 4 amps or something like that as the tubes come into a mission this is going to go higher and then this is going to drop back so then all you do is you would take this if it drops say down to 4 volts or something like that you would take this and you would raise this back up to 6.5 and of course you'd see the current move a little bit here again and then once everything is settled off you're at the perfect spot that's easy to use and then you if you shut the vacuum tube radio off what's going to happen is is this is going to go way up here and then of course it's going to drop off right because you have no current draw but as soon as you turn it back on again this is going to you know pop back down again and then this is going to pop back up so you know very useful power supplies now you might be asking yourself why not just get a modern regulated power supply and use something like that well when you're drawing lots of current from heavy inductive loads and things like that even some very large non-inductive loads like filaments and things like that their cold resistance is actually very low and then as they warm up the resistance starts to go high so it starts to go higher well a lot of modern power supplies unless they're very overrated don't tolerate that stuff very well and if you have a nice big power supply that has say to3 pass elements on the side of it and i say you attach some you know big inductive load to it or some you know big filament from a transmitting tube or something like that you risk destroying all those pass elements again you have to have a very heavily overrated power supply to do that there is almost virtually nothing in a supply like this that will fail like that all you have is diodes a transformer and some filter capacitors and in this case it's a little fancier they've given you a variable uh transformer here to adjust the voltage but most will have just taps on a transformer that you just move a selector switch and it moves the taps and you know if diodes a bridge rectifier or you know just a full wave setup and some capacitors and if you're the regulator and you start off at zero and bring up say a filament on a vacuum tube a very large vacuum tube you're absolutely fine there's no problems and you can monitor things as you're bringing it up you can bring it up very slowly and get those filaments warm so that they're actually not at such a low resistance as well again when you're dealing with very large you know power tubes and things like that when the filament is cold you know it's a pretty nasty load until the thing is warm right so at any rate these have lots and lots of uses again battery chargers dc motors you know working on vacuum tube radios things like that lighting up incandescent bulbs or working large vacuum tubes testing filaments and things like that lots and lots of uses i have not this particular supply but i have probably oh six or seven supplies like this just known as brute force types of supplies where as long as you're careful and you bring things up slowly you're absolutely fine and you're not risking the pass elements in your very very expensive high current power supply very handy to have these things on the bench very handy power supply to have again as long as you get comfortable with using it there's no problems in using this now you wouldn't want to use this with modern car radios right unless you're very experienced with the power supply and you wouldn't want to use this with more sensitive devices right because again you're not very fast right you can't move this and compensate quick enough like a like a regulating ic can you know compensate and move the uh move the pass elements around to supply the current right you you can't do that as quick all right i dug up a schematic on this thing let's take a look so first of all we have our transformer with the variable taps somewhat like a i guess you could say almost like a dual variac type of design and that's this right here as you can see the little moving contacts down here moving along the windings that's kind of neat neat transformer this isn't something you see every day that's a pretty specialized device right there we have a bridge rectifier here so this is a full wave bridge rectifier here and they've done something really neat by the looks of it i'll explain this here in just a moment so you can see on 12 volts we're using the full wave bridge rectifier from basically from end to end all right so we're using so obviously this is is doing this in reality right so it's going to be moving up and down the windings like this so he's using the windings from end to end so we can see the the positive portion of the bridge rectifier so the positive portion of a bridge rectifier is where the two diodes face each other and the negative is where the two diodes or the backs are are at this end here right and then the center portion where they kind of look like they're in series goes to the ac windings is a very easy way to remember a full weight bridge rectifier so you can see this runs out here and then this runs through a 5 millihenry choke here or coil if you like l1 which is this right here nice big you can see the size of the windings in there it's huge they look like probably wound with number 10 wire or something like that so that would be number 10 insulated wire in that so nice big coil here and we have a capacitor on one side of it so that would be one section of this capacitor here would be on one side of it right on the bridge rectifier side and then on the other side we have another capacitor so we have a typical pi network type of filter that's what that's known as and then we have a voltmeter here which is across this 0 to 20 volts and then in order for it to read current it needs to be in line with the load right so this would be the current meter right here and we have a switch now this is where they've got kind of tricky this is kind of neat so what they've done is when you click this switch over alright you can see this dotted line this means that these contacts are ganged together whenever you see this in a radio with capacitors or whenever you see this anywhere with switches with the dotted line that means that if you move this one to the other contact this one moves to the other contact okay so if we move s1 from the 12 volt to the six volt position this one is going to move from the 10 amp to the 20 amp position here right here and this looks like they're just adjusting the uh the meter here right so this is this is our probably our internal possibly they're adjusting the shunt inside the meter anyways when we restore it we'll find that out at that time so if they click this to six volts you can see immediately that now we're using the taps right directly out so it's we're completely eliminating this right so we're not using these two diodes here right now we're just using the taps and this runs straight out so what they're doing is they're actually switching from a full wave bridge rectifier to just a full wave setup using these two diodes so the two diodes they're using are on the negative line so they're using this switching this to this portion here so we have the the winding running straight out right and then on the negative line because now we're dealing with full wave rectification we don't have a full wave bridge rectifier but we're dealing with full wave rectification you can see that we're using these two diodes in the return line here and that's what's running on here so we actually have a rectification over here which is kind of neat very inventive so in order to give you that switch back and forth it's just a very cost effective way of doing things of course it's absolutely fine right because the case is isolated and everything from what you're testing right so very very neat whether you have the diodes on this side on the positive side or on the negative side you're still getting full wave rectification it's just that you're placing the diodes in a different spot so very very neat so i don't know if you can picture this you can see that with this in the 12 volt position okay you can see we're using the full full wave bridge you can see that this is disconnected right you can see that this here is just disconnected and what we're doing is we're moving this up and down the windings like this so we don't need a connection here because as this goes closer to the ends of the winding we're going to get less voltage and then as this goes towards this right because we have more windings we're going to get more voltage right here so what we're doing is we're just varying these windings between each other right now on the 12 volt position because this is open so we have a full wave bridge rectifier so you can see the ends go to these portions of the bridge wave rectifier so the ac input and then we have the two diodes that face each other running out right to the positive side and then we have the current meter all on the negative leg here okay so as soon as we click the switch to six volts these two diodes are no longer working anymore but these two diodes are still in circuit because of course these are fixed to the to the end legs of the the outer portions of the windings i guess you could say so when this is in the six volt position here this is running to here this is running to here but this is open so we have this is our positive side and we've just basically we're using the negative portion of the br the full wave bridge rectifier we're just using these two diodes and the diodes are in the return line very inventive very neat kind of design here and again of course this is moved down to here to adjust the shunt on the meter to make the meter read correctly so whether this reads correctly or not i'll have to load test this and we'll do that when this gets restored so this is a neon bulb that's what a neon bulb symbol looks like it looks like two plates sometimes they have a little dot in there indicating that it's a gas filled bulb but this is just how they're indicating it here it looks like a capacitor symbol in here but that's that's a neon bulb symbol and we have a 33k current limiting resistor in line with a neon bulb neon bulbs always need current limiting resistors in line with them because when they strike or when they light up if you like uh what happens is they immediately go to a low resistance state so as soon as they as soon as they strike or light uh if they're basically it looks like an open connection almost until that point but when they strike immediately they they go to a low resistance and this is what's limiting the current so you can make relaxation oscillators with these things and do all sorts of neat things with neon bulbs you can do all sorts of neat little projects with them oscillator circuits if you like and all sorts of things like that k1 here would be this right here so this is just basically a thermal type breaker an automatic resetting thermal type breaker so if you try to destroy the supply this says you're not wrecking me you can't do it i'm gonna cut the power so that's what this does and then when it cools down it reconnects again and realizes that you've shorted the output terminals and then opens up again and it'll just sit and cycle so this is an automatic resetting breaker right here we have the fuse here three amp fuse in the front here with this funny looking holder that somebody's added to this but it looks like it's holding the fuse in place the switch which is you know the on off switch and then um we have the selector switch for the 10 and 20 amp which is on the other side here on the other side moving around we have the diodes and the full wave bridge so this is the uh the diodes in the bridge they're all separate diodes they don't have a an actual like just a square bridge type rectifier so they've wired these up like this basically a nice big high current bridge and as you can see they're isolated and these two diodes right here are on a heat sink and these two are on their own nice heat sink so very heavy unit uh the bulk of the weight is of course these two the reactor here or uh choke coil if you like in the uh the variable transformer and then of course our filter caps that's very simple design very very simple design and i like stuff like this just because it's again so brute force you know there's almost nothing to fail in this thing you know with these big stud mount diodes you know good luck with this power supply opening those things up or turning them into jumpers i should say because diodes uh when you make diodes unhappy they usually turn themselves into jumpers they transform themselves into just a jumper from one side to the other those of you that have been in electronics know exactly what i'm talking about and yeah that's it so there you go i hope you enjoyed this and maybe you'll learn something in this episode if you did you can leave a comment below and let me know in the comments and uh there'll be a lot more of the stuff we'll take a look at that weird-looking scope that uh that i discovered here not long ago with that big crt sticking out of the front we'll take a look at that and have all sorts of other neat projects that we're going to go through and take a look at schematics and analyze everything and of course if you're interested in more of this type of stuff and a lot of the circuits that i've designed myself my inventions and stuff definitely check out my patreon i'll talk about that in the end of the video there and put a link just below there's uh an ongoing electronics course that's very very active on patreon lots of neat circuits and projects for you to build and lots of explanations like this and and very in-depth ones with looking at scopes and all sorts of very neat things up there so definitely check that out if you're interested in this type of stuff if you're enjoying my videos you can let me know by giving me a big thumbs up and hang around there'll be many more videos like this coming in the near future we'll be taking a look at vacuum tube and solid state electronic devices alike so if you haven't subscribed now would be a good time to do that as well if you want to be notified as soon as i post a new video don't forget to tap the bell symbol if you're interested in taking your electronics knowledge to the next level and learning electronics in a very different and effective way and gaining access to many of my personal electronic inventions and designs you're definitely going to want to check out my ongoing electronics course on patreon i'll put the link just below the video's description under the show more tab and i'll also pin the link at the top of the comments section so if you click on the link it'll take you right there alright until next time take care bye for now you

Channel: Mr Carlson's Lab

Views: 55,620

Keywords: Mr Carlson's Videos, power supply repair, fix a power supply, test a power supply, power supply design, electronic engineering, use a power supply, understanding power supplies, test equipment, circuit design, reading schematics, understanding schematics, fix electronics, repair electronics, restore electronics, rebuild electronics, restoration videos

Id: zmEZ6LInQ8Q

Length: 25min 47sec (1547 seconds)

Published: Sat Nov 20 2021