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[Music] today's episode of radio rama is brought to you by the california historical radio society a non-profit educational 501c3 corporation chartered by the state of california in 1974 to promote this research restoration preservation publication and presentation of early radio and broadcasting you can find out more about us at californiahistoricalradio.com [Music] hello everybody and welcome to another special edition of radio rama and in these shows if you watch my others we tend to work on tube powered electronics from the 1920s through the 1960s and today i decided to do something a little bit different and so as a forewarning this episode is geared more towards beginners who might not have restored a vintage radio so if you're an experienced seasoned electronics guy this might be boring so feel free to skip this episode otherwise if you're just getting your your hands dirty i'm going to go over some basics and we're going to restore a very very basic five tube an american set these are known as aa5 which stands for all american five sometime in the i don't remember exactly when i think it was the late 30s early 40s a design came out with a simplified circuit that did not require a transformer and these are called hot chassis sets because how it works now you think about back in the good old days when you have well i guess a lot of people aren't alive that had christmas lights like this where you'd have a series of light bulbs strung together in a series and if one bulb went out then they all went out so it made a loop electrically the same deal is with these radios there's no transformer but one end of the cord goes in from one end of a string of tubes now this radio has five tubes and so what was needed is the cumulative value of 110 volts worth of filament and what is a filament so a filament is what makes these things glow there is a filament in the middle think of it just like a light bulb filament it glows like a dull orange and that filament will have a certain rating so this is this is a 35 c5 and what does the 35 stand for the 35 stands for it takes requires 35 volts to power that filament now this set unfortunately the the ink the stamping is not very good but i almost guarantee what all the tube filaments and the tube types are the rectifier which is well the rectifier tube is probably rated at 35 volts the output is rated at 50 volts and then the remainders are all rated at 12 volts you put that together you get about 111 volts worth of filaments or thereabouts before we go too much further i'm going to talk a little bit about safety these are not necessarily up to united well underwriters laboratory specifications by any means uh some of these can actually be a little more dangerous than others some hot chassis sets actually have one end of the line literally going to chassis but we'll take a look and see what's going on with this guy but let's go on to talk about safety these guys operate on fairly high dc voltages if you touch the wrong thing you can get a little bit of a nasty zap on certain instances that could potentially be lethal so just be aware that if you do not feel comfortable doing this then don't do it now number one most important thing that you can have in your shop when you're working on electronics now it's hard for me to see as good of my tools hanging away this is an isolation transformer now what that does is electrical current will always try to find the easiest means to get back to ground what that isolation transformer does is it guarantees that it provides the absolute easiest path to get back to ground that doesn't mean if you were to touch the wrong thing you might not get a little bit of a jolt but what it does mean is that the ground is going to favor that ground more so than you the second thing that i recommend you get is something called a variac and what a variac does is it allows you to control the amount of voltage from zero to however high it goes that way for testing a piece of electronic equipment you can bring it up slowly and if something starts not sound right you can turn it off i usually start at about 50 percent so the first thing that i'm going to do is test the set now some people say don't do it that's probably not a bad idea i've already actually tested the set because what we're going to do is something called a recap job now a recap job means replacing capacitors and what does that mean well once we get inside this set i'll show you what that means but essentially we're going to replace the most failure prone components that happen to be in radius it's not the tubes a lot of people think oh the tubes must be bad tubes are probably actually the most reliable item in your radio they can last as long as you know it can last decades and decades the thing that fails the most is going to be capacitors and especially the electrolytic capacitors so i'm going to go ahead and plug up my variac that noise back there is my washing machine which seems to always be turned on whenever i do these shows turn this head on turn my variac on i'm going to bring it up just initially to 50 percent see 50 is basically 50 of 110 which this thing works on and uh what i'm also going to do is kind of see a look in the back see if i see any filaments now it's hard to tell in this video but i'm already seeing a little bit it's very faint so far nothing is immediately smoked so i'm gonna bring it up a little bit more there we are again i'm gonna look for filament because if i see no filament that means a set will not work i am definitely seeing filament let's go ahead and bring it up the rest of the way now i know what it's going to do because i said i've already tested it all right did you hear that that awful sound that the buzzing noise so that is absolutely the number one problem that radios have the electrolytic capacitors are shot so before i go further i'm going to take this apart and we're going to start talking about the basic construction of an aa5 all right so i have removed the chassis and i'm not sure if this is actually the best set to start with it is so basic there's not a whole heck of a lot going on here but um just as a little note standard in american electronics for holding chassis together tends to be a quarter inch bolt and so to make your life a lot easier if you get yourself a quarter inch nut driver it's a lot easier than using a pair of pliers so you might want to invest in one of those now where we're going to do all the work is underneath and now we're going to talk about different types of capacitors and there are generally two different kinds we have an electrolytic capacitor and an electrolytic capacitor you can tell usually they're physically quite large and also there's a rating on these guys that's expressed as microfarads or you'll see a little symbol sometimes it says it's like a lowercase u and a big f this case it's abbreviated microfarad and there are two values they often did this back then where you'd have one component that would have two different capacitors stuffed inside the same cardboard tube and so this guy has two different values we have a 50 microfarad and a 30 microfarad and you'll notice off to the right hand side it'll mention its its voltage rating which is 150 volts dc with a five tube radio you're never going to see it anymore higher than that because we're just talking about incoming line current which was 110 back then 120 now and you'll notice these are also color coded we have a red and a green now red if you've ever taken art class is really fugitive meaning it fades pretty easily so this this is a red it's faded to this weird sick yellow color green is less fugitive so by default you can tell like okay this is red and that's green so what what we will do is replace this component with two individual electrolytic capacitors so that's one type of electrolytic and they have a they have a shared common ground by the way and this is what's causing our awful hum the other types of capacitors that are in these are generically called paper capacitors and the reason is because what they did was you had a foil that was coated in a dielectric paste compound i think it's a borax material i'm not a chemist and that's wound into a in fact i've got one here that came out of an earlier radio i was working on see the cover is coming off of that it's essentially really tightly wound aluminum and how it works is that in between the sheets of tightly wound aluminum you can get a dielectric static charge so this is a paper cap and that is a paper cap they have much much much lower uh capacitance rating it's a fraction of what these are and they are also not polarized it doesn't matter which way you put them in now i can tell someone's been in here because you see this orange guy that's that's a much later replacement that was probably done in the 60s maybe even 70s that's the thing these radios even the cheap ones were not cheap by today's standards a radio like this would probably have cost you 20 bucks or more which in 1950s dollars if you think about it if you're making a buck an hour or less it's like i'm not doing good at math but you're probably talking about 150 bucks for a little shitty radio so people tended to keep their their sets for for decades because the pain of remembering of how much that cost was on their minds so these guys also tend to have their values written on them on the sides um that said when i opened up when i saw this was a motorola i knew it was going to have something weird in it this is probably again this is why i'm thinking this might not be the most perfect set for a beginner but where did the wise if you see a motorola that has this component this is resonant at 455 kilo cycles then this isn't just a capacitor this capacitor on this end has a little coil and that coil essentially resonates with the the if signal which is as you might have guessed 455 cycles now let's talk a little bit more about how to replace what with what so there's kind of a controversy about not really a controversy about the golden rule about replacing capacitors is this electrolytic capacitors as long as the value of the microfarads is at or greater the microfarad rating you're good your voltage needs to be at or greater for sure it can't be lower now that's true to an extent you can probably get away with up to 50 more microfarads on the rectifier side what i mean by that is one end of this line the red one goes to the bottom of that tube which is 35w4 that is our rectifier if you put too much uh microfarads on that you can stress it out a little bit um i've had no problem putting double the value but that's kind of stupid you're just wasting money um and and there is a lot of tolerance with these guys you don't have to put exactly like i they don't even sell 50 microfarad caps anymore so you can use a what you generally buy these days is 47 microfarads at 160 volts and that'll work just fine so i'm going to show you what we're going to replace these with and i should have gotten these down before i started so this is going to show you what the difference is between an old capacitor and a modern one we're going to replace both of the electrolytic capacitors inside with two of these now again these are polarized so how do you tell which end is polarized or which end is negative it's easy you see this stripe that has a negative symbol that's your ground so by default the other one is positive what we also want to do is try to figure out where is ground so the ground wire comes up over that's a really kind of ridiculous path it goes to the other side of the switch and then the switch goes back through here to what appears to be it's hard to tell without me lifting some out of the way first if tube now we were talking about this one of my radio friends today theoretically yes you could run your common negative of these electrolytics off of that if2 but then you would probably have some nasty humming going on so we're not going to do that instead what i'm going to do is the opposite way so you just follow the leads of your positives first positive goes off of this lead coming off of again the rectifier tube so the positive of this capacitor is going to go there the negative will stick out and we'll run wiring from the negative coming off the back of the switch to the negatives of each individual electrolytic capacitor we're going to replace this first because that will probably cause the set to work and then we can proceed with the rest of replacing the capacitors okay so now the electrolytics have been replaced and every radio that you get in is going to always be a challenge about where to stuff things and this one is a little bit more of a challenge because the way it mounts is that the the bottom of the chassis faces inward in that way and so you want to make sure that none of the components are going to hit those mounting posts so what i've done is i've stuffed them kind of in this area and what i've done here is you want to keep your leads as short as possible so if you look here you can see the two negatives are conjoined here and then we have our original uh negative lead coming from the switch connecting to these two shared negative leads and then we have one positive going to if the other positive going to the rectifier tube so now that we have established uh well one now that we have we installed these new electrolytics i'm going to put the tuning knob on here and attach what i call a cheater cord i'm cheating because i'm basically negating the safety feature this radio came with it's already turned on ideally even if you've got a isolation transformer you kind of want to avoid touching the metal chassis so now i just have a little control uh via the tuning knob so now i'm going to plug it in and we do have filament so that's good nothing is sitting here sizzling away and we'll see if we're getting a life out of it and again i'm sorry about my stupid washing machine [Laughter] all right so you see the set now works works well actually but we ain't done yet we're not done because uh i want to talk about something really important the thing that's really important is like i said there's a difference between a true hot chassis where one end of the actual cord goes to the metal chassis and then what is referred to as a floating ground chassis meaning that there's something else that the uh set goes through and there's something else the juice goes through before it goes to ground in this case it's this capacitor slash uh resonant coil on the end now i've worked on this model before that that value is basically a 0.2 microfarad capacitor that means that still if i were if i accidentally grounded myself and touched the chassis which on this set would be pretty damn difficult because we've got a pretty solidly attached back i would still get a pretty significant jolt and standards back then for what is known as heart fibulation was not as well understood in reality this would cause a heart to fibulate if it went across your chest the wrong way so what we're going to do is put in a value that makes it more appropriate we're going to use one of these this is a .01 rated uh it's called a safety cap it's called an x2 across a line 250 ac rated i believe it's a 2 kilovolt which means 3 2 000 volts dc and again this is a weird one only motorola did this so you won't encounter this very much i'm going to detach this and cut it open and remove the coil i believe the coil is is on this end and then we will attach our new grounding cap and if you're just starting this i'd highly recommend you replace one component at a time and then test to make sure that you haven't messed up keep track of where you are and what i generally recommend is you replace one lead one end at a time and there's a couple of tools i use everyone is inclined to use their own but these are the three that i've used forever i particularly like klein kl well there's two brands klein and exalite they're both old-school american brands these are both exalites a pair of pliers little nippers these are i believe these are kleins they're a little bit more spendy but you know what like i've had these guys for years and the some of the chinese stuff just you know get you what you pay for um so we're gonna cut this guy out and take a look inside and see where that coil is okay so all i did is i took my little box cutter here and i just cut the outer cardboard edge here's our resonant coil it doesn't look like much i can tell you from experience the radio will not work without it so be careful do not try to deform that and this this end is what goes uh to this pin coming off of i believe one of the rf tubes yeah it's 12 be6 so we're going to replace this old paper capacitor inside with the safety cap and attach it to the under the other end of the resonant coil and then we're going to test the set again to make sure that it works now something i forgot to talk about is soldering i'm going to talk about two things i'm going to talk about soldering and lead dress now lead dress just means like how short you can make your leads now if you look here this is the replacement i've made the leads as short as i can to go back and forth between these two this is a little silly that was probably made by another repairman this could be shortened i'm going to get it out of the way i use a kind of a professional soldering iron called a metcal they have replaceable tips they're about 500 bucks they're worth it because for me because i use these every day weller makes some really good soldering stations stations meaning that you have a controllable module and a stand uh you can get one of the just the plug-in ones as well depends on you but what you want to do is and this is crucial here is make really good soldering joints so what you want to do is touch the work meaning the surface first and get it real good and hot and then you just want the solder to flow in that joint wait for it to get real good and molten so let's take a look at that joint you see how it's really uniform and um kind of has that shiny appearance again a real hot joint is what you want i i find with a lot of newbies it's real tempting to kind of just barely tack stuff in is barely stick it in um again you want a real hot joint that sounds kind of funny so what we're going to do now is do a few other little pieces of housekeeping here first of all we need to oil uh the tuning condenser now the tuning condenser is basically referred to as like an air condenser we have these little plates and what they do is they they go in and out of each other these two plates like essentially act like a sandwich be real careful if you bend these sometimes they're really difficult to bend back but the the air gap between these two serves is like a kind of a fat condenser similar principle to a regular capacitor now it's got ball bearings in there and they put grease in there in the factory back in the 50s and it's solidified so now i'm going to use a teflon based oil you can also use a light machine oil we're just going to get those bearings nice and wet and now we're going to turn that back and forth a whole bunch and work that in it's already starting to feel a lot better you don't have to do this but it just makes the sensation for the user so much nicer as an addition i usually do this to the volume shaft as well as it has tone controls which this doesn't you can see i'm putting it right there where it makes the joint you work that in and again that feels a lot better the other thing we're going to do is clean the pot the pot is is the true name for it is a potentiometer and we're going to clean that with some part well electrical contact cleaner and you'll see these three legs here that go down into the pot you'll notice there's kind of a gap here so i'm gonna get my cleaner and get your little straw and just spray some in it then again you work that back and forth a bunch what there is there's a little contact surface and a kind of a carbon-coated plate and sometimes dirt will get down in there over the years and you want to clean that off that already feels a lot better likewise what we want to do is lubricate the other side of the bearings on the tuning condenser and also this little on the end here because believe it or not this this is part of the tuning condenses contact so you want to clean that as well so now that's feeling a lot better it's a lot cleaner probably the little radio is breathing a sigh of relief and what i'm going to do is a final test to make sure that we're still working now that we've got the radio electrically restored more or less we're going to take a pit stop and talk about equipment so you can get a lot of things done with one important tool this is called a multimeter and i think this is about 135 this is a fluke model 115. from for most people this will be totally totally fine i've had this meter for years fluke makes really good stuff it's a professional brand so that's a digital multimeter i also recommend that you get a analog multimeter this is a simpson and uh i forget the the model number of it but simpson actually still makes this model it's an american company that um somehow man os simpson 269. they still make versions of this um the other thing that you will need eventually is a tube tester now tube tester prices can really go all over the place i actually don't have i used to have a very basic tube tester but i wanted to show kind of two different general types there is um what are kind of referred what i call like the flipper model type tube testers where you have to adjust these different levers depending on what the chart says we look at this chart here here it shows you which settings to set here so we've got one two three four five six seven eight nine ten eleven thirteen fourteen you can see this goes all the way to fourteen so you can just set depending on the tube type your little levers there are this is a dynamic mutual conductance tester and then there are other basic ones that do not have that feature a basic tube tester that has levers like this you can expect to pay under 150 maybe as little as 50 bucks now i don't use this one that much anymore it's still a nice machine my primary daily driver is this this is a military grade hickok model tv7 and these are kind of like the rolls royce of tube testers they're just extremely finely made they're bulletproof this one even has a weatherproof seal so you can seal it up in bad weather um they're they're excellent because there's when you get inside there's not really anything to fail this has a mercury vapor tube that's it i think there's one electrolytic capacitor which i've replaced but the unfortunate thing is that a good one of these these days is pushing a thousand dollars and you can even upgrade these there's a few small companies i think in california that are making modern digital meters i don't really care i'm totally fine with a i'm totally fine with a analog meter now the other things that you'll need to get once you start getting better at this this is a an rf signal generator and that's these are important because what that does it's literally this is like a radio it's producing a 455 kilo cycle signal that you can use to inject into your radio if you're not getting any signal you can use it to trace down where the signal has broken and if you want to get even fancier you can get yourself an oscilloscope this is a tektronix model um i think uh remember the type r561b now what's great about equipment these days tektronix is still around and you can spend ten thousand twenty thousand dollars on a piece of their equipment easily this is a 1963 era tektronix i looked it up back in 1964 this would have cost you over twenty six hundred dollars think about just that for a minute ford mustang was 2500 bucks these are unbelievably finely made you can pull these out all the components are held in with real silver solder on um ceramic bases these are so good that oftentimes they just still work i mean if you look here i guess i'm getting off on a tangent here see those capacitors those are called vitamin q capacitors and they're ceramic sealed ends these cost a fortune back in the day they do not fail and so that is what you get with no expenses spared quality these were used in labor laboratories and by the military but at the very minimum you should have one of these and i already showed you the variac and the isolation transformer which are key whoops it just knocked the phone and so all right i just wanted to show you a little bit of that before we get to the last part of the restoration which is the owner of this radio requested that i add an audio input meaning that he can switch the radio section which is the radio signal off and on and then plug in an audio device to listen to music all right so there's going to be the here is the last part of this restoration and this is optional if you decide that you're perfectly happy having a properly functioning am radio then the electrical restoration i just showed is done however a lot of people that i've restored sets for they want to be able to actually listen to music on them because depending on where you are am does not have a lot of music on it anymore and so how we're going to do this is with these parts and i'm going to identify them one at a time this is the the jack that you can plug up either to your phone or a bluetooth device or if you still have a cd player mp3 player whatever this is called an isolation transformer it's a miniaturized version of the one i showed you earlier it does the same thing this is going to isolate the user electrically from any potential shock hazards which even even though i have already put a safety cap on this minimizing that that risk this will eliminate even further to well where the user could you know touch this and stand on ground and not feel a damn thing that's important we have a switch and the switch is important because what we need to do in order to enable the user to not have their audio polluted is in a means to switch off the signal coming in from the radio signal because this basically this has a miniature tube amp in it the tube amp is amplifying the radio signal and so all we're doing is we're temporary you can temporarily switch off the radio signal and just use the amplifier section of the set now the last thing that's part of this is that obviously this has a right and left channel it's a stereo jack and while we can't make this stereo we can at least join the two signals together to get mono so you still capture you know the full spectrum of that audio you won't get separation but at least you'll get true mono what they call it and you can't just you can't just like stick the two ends of this together if you stick right and left together you're going to stress out the incoming audio device you can possibly damage it but we can eliminate that risk by putting a pair of resistors in front of it and what will happen is that we will tie these two ends together that goes to um the incoming audio off of this volume pot which is going to be this side and i'll get to that just a second and then we can run the right and left channels individually coming off each individual end of the resistor now this has two windings on it and you can they're separated by you can tell what they are because they're separated more i already scraped this off but it indicates which pins are which we have a primary and a secondary winding this is the primary this is the secondary and what's going to happen is that we're going to mount it here you want to get it as close to volume as you can and our primary is going to go to either end of the volume pot it will go to the ground side which is this side and the incoming if signal side which is this side it's easy to tell which ground is because you know here's our shared ground for our electrolytics likewise that is also going to this leg there's three legs and you don't want to use the center one because if you try to solder your positive to the center then the device controls the volume versus you versus the volume itself being the control volume for the incoming audio and what i do i found that super glue and roughening up and cleaning the two surfaces this will stick there and you won't be able to get it off so i'm going to mount that on there and then i'm going to wire this up and go into detail to show you how this works once i've done it all right so this is the end result of adding audio input and i'm going to kind of reverse engineer and talk about what we discussed earlier which was the two resistors you see we've got the red and the white leads coming from the incoming audio that's your right and left channels and they terminate together on one end of the secondary part of the isolation transformer ground goes to the other likewise on the primary we have one end going to the [Music] rf side positive side of the pot and then the other goes to ground what i've done here is i've snipped this lead used to go to that part of the pot and i have my switched line it's excessively long because i'm never sure how long i need when i put it back in the cabinet and then i can snip it the idea is you want to keep everything as short as possible and i'll try to keep everything away from potentially uh causing rf pollution if you start running wires through areas of the set that are used for reception like over in this section you can start to get some interference but everything here is kind of on the edge here there's not anything in the way and the other thing i did was that you tie a knot and the cord and also what it is i put a little glue on it so it's in good shape you can't yank it out of there um the last thing i'm going to do well actually what i'm going to do is i'm going to i'm going to demonstrate this i've already tested it but i just wanted to give you an idea of what this will do so right now because i don't have a switch the let's make sure i've got this on is it on yeah it's on okay anyway it's warming up so i've got this little bluetooth running through it okay so we've essentially got a good connection with the audio input the last thing i'm going to do and this is just it's up to you it's your to your radio whatever makes you happy i'm going to clean this guy up and probably wax it it's got some scuff marks on it but as you can see how dull this is it's just dull from i guess everyday use and you can use a product there's nothing scientific about it or crazy i'm just going to use an old-fashioned car noob car wax i use mcguire's it's been around for a million billion years it's just a plant-based wax and i find the synthetic doesn't work very well synthetic waxes don't work that well so we're going to clean and wax this guy up and we'll put it back together and we should be done okay so the set is now done and so what i did here is i i cut the the length of the switch cord so now we either well let me unplug this down is respect for your opponent if they're self-employed if they're unemployed they don't have to go get a shot so we have the radio section if we want to disconnect that and then we plug in sorry i'm doing this one-handed with my phone now we've got our bluetooth running in [Music] [Applause] doesn't actually sound that bad for such a shitty little fob tube radio so your last task is to let it run you've just successfully restored a 60 plus year old piece of electrical equipment most of the radio is still 60 years old including all of its components so with age comes deterioration in parts and with parts that have been out of service for decades it's best to let stuff run for a while to make sure that nothing's going to break because the last thing you want is for the customer or you to have to go back in and repair it so you want to make sure you've got all the bugs worked out most the time they will just work i've had a few things that'll really up uh these things of course the genera the tubes generate heat the resistors generate heat things get quite warm in there it turns into a little oven and so there can be some thermal resistance and breakdowns uh once again components that have been out of service for decades get to that point so i tried to make this as basic and as understandable as possible now if some of you beginners watch this and you're like we left some things out let me know i might make another one of these in the future it's hard to for me to describe things that i've been doing for many years and try to remember all the things that i didn't know when i first started so i hope you got something out of it uh maybe even some of you brave souls that decided to sit and watch it even though you've done this a million times and if you have any questions or comments you can always leave them in the comment section down below and um until the next piece of electrical device comes across my workbench i'll see you next time so