Restoration Inspection - How Well Did They Do?

hi everyone and welcome to another episode of mr carlson's lab let's get started quite often i get the question paul would you mind going through this radio that i've purchased i've been looking for a radio like this for a very long time and i finally found one that's been restored would you mind going through it and just checking it over to make sure that it has been restored properly if it hasn't can you address any issues that may have been left behind or you know address the whole thing if it hasn't been restored and that's what we're going to do in this video we're just going to basically look at this radio we're going to see what's been done to it because supposedly the previous person has restored it and we'll talk a little bit about the things that should be done and a little bit about the things that may not have been done again we're going to discover all of this together this thing might be beautifully restored inside i don't really have any idea so i was going to do this off camera just take a look at the radio and see what needs to be addressed i figure hey maybe i can share some tips and pointers with all of you and maybe you can use this towards your next restoration yourself so grab yourself your favorite beverage i've got mine right here and let's analyze this radio and see how well it performs so what i'll do is i'm going to get the thing plugged in and i'm going to loosely couple my external antenna to this because there is no external antenna connection to this and we'll see if the thing receives to start and we'll go from there the radio is attached to my isolation transformer and current limited variac supply because i really don't know what i'm up against here so what i'll do is i'll turn this on and see what happens so i don't have any external antenna attached this is just the antenna in the radio so their antenna that's on the back portion we'll see what happens now there's noise all right scan the band so before i do this this area is pretty much an rf dead zone so if this thing is receiving stations in here it's doing all right if it receives nothing well that's to be questioned at that point it's got static so it sounds like it's trying you hear that there's a station there a little bit of a station there it's trying it's a good sign all right so what i'll do is i'll just put this about mid band we'll start there again so what i'll do is i'll take that 369 antenna that i just built and grab that same inductor that i used and uh click this on here put this close to the back portion of the radio do whatever it takes no matter how many times it takes uh somebody to throw they can look at this that's just from holding this inductor close to the antenna [Music] so the antenna is coupling in quite well and the radio is working not too bad not too bad at all i notice that the upper portion of the the dial isn't receiving a whole lot right now so that could just be conditions or you know could be a multitude of different things but all in all the radio receiver itself is is performing very well the fact that it can even hear radio stations in here with you know without the coupling to the external antenna is uh pretty fantastic just just the way it is so i would imagine something has probably been done to that just for that fact alone so what i'll do is i will unplug this here set this forward the radio itself is the bakelite is in very nice condition so somebody has done some dial gluing here i'll just zoom in on this so somebody has done some dial gluing in here and glued the dial in i don't know how incredibly straight they got that doesn't look like it but it probably can be chipped away and cleaned up it does it looks like it's kind of a glue that really hasn't taken all that well so that's kind of a nice thing because that can be cleaned up and maybe this doll can be cleaned up and straightened out a little bit the bake light itself looks like this after a while it usually discolors there's so many ways to make this look good you can put a little bit of car wax on there some car polish sometimes some orange and lemon wood finishes seem to work very good on this as well if you rub them in and dry them off it makes these things look like brands spanking new again so for a period of time and there's a whole sort or all sorts of other ways of of making these things look good if you're interested in you know something that's very very permanent and cleaning the thing off completely making sure the bakelite is nice and dry and putting a clear coat on it a lot of the times makes these things look absolutely gorgeous too so there's a lot of different ways of doing things as many of you know i'm working on the the new lab so this is one of them here and i'm working on another one that's a very large one and we'll go over some cabinetry and bakelite stuff out there as well so coating these things with special paints to make them look very good something that'll last for a long period of time the knobs themselves look like they're in very nice condition so no problems there i've noticed the plug itself somebody has taken the time to put a polarized plug on this which is nice so this looks like uh you know some early form of lamp style plug or something like that i do notice that there is some heat shrink tubing on here and it looks like somebody is glued a cardboard piece onto this so they've actually taken this looks like the backing to a paper pad is what it does normally the little cardboard piece that fits on here is uh you know has a shellac or a varnish on it and it is a somewhat of a flame proof design but this is just a standard cardboard that they've put on there so something that could be taken off and improved it's nice that this is on here this comes with a few catches putting the polarized plug on here and i'll talk about that here in just a little bit so already a few things that that could be addressed with the case uh the backside looks very nice this looks almost spotless so very very nice uh very very nice uh back or cardboard back on this the screws on the bottom everything looks original this is probably there was a schematic or something here at one time which is missing so the schematic for this model is relatively easy to find and this is the series one they made a series one and i believe a series two so this is the series number one here so i'm not going to take the back off because you don't need to take the back off of this usually what you do is you just pull the knobs off the front and take the screws out of the bottom and the whole chassis will come out and we'll do that here in just a moment okay let's take a look inside and see what's been done so first things that we need to do here is just take the two knobs off and we'll remove the screws on the cabinet which is only three of them they look original so which is a really good sign so a lot of the times you see you know self-tapping machine screws thread in here and you see all sorts of things i've seen it all so okay so this one here should probably allow the radio to pretty much come out and as you can feel it trying to slide backwards now these radios are kind of interesting because they've got this top and the cabinet won't slide straight out so you have to tip it because it gets caught on this so let's hope i can get this all in here let's put this here so that's as far as it'll come you can see how this is hitting this one point here so what has to be done is the chassis has to be tipped forward like this and then brought out like so so let's take a look inside here it's looking pretty good now you can see that nice and clean up there so it looks like you can carry these things he has like a vent hole up here it looks like you can almost carry this around like so but i imagine that would be kind of a dangerous thing to do because brake light bake light is uh is a little bit fragile by now it looks like they also intended this possibly to be replaced so if you broke it by carrying it or something like that you probably take these out and maybe replace this one piece did bakelite just become brake light that was interesting okay let's move this over like so well immediately i see some kind of interesting stuff going on here just on the top so it looks like they've added some tube somewhat of a tube retainer and they've soldered this on here to hold the tubes in place this looks like a shield that's been added and another one that's been added over here so this one here looks like it could be factory i added this retainer over here and another retainer over here these little retainers are very common for for the early radios from japan they had these in them to hold the tubes in place but this looks like this might actually just be a bent piece of wire or something like that i don't know it's kind of neat would hold it in place for travel or something like that if this was to be you know shipped or something like that the tubes wouldn't fall out why this is soldered to the chassis over here maybe there's some form of an oscillation issue or something like that see a wire has been replaced down here and yeah so let's take a look at the speaker the speaker looks flawless so that's very nice the spring be careful with this back here i'm just going to hold this like so so this spring that holds the the dial string tight there's pretty much no tension on that so what that tells me is the dial string is probably stretched over time just a little bit and sometimes that can be fixed up by just moving this up a little bit and that'll put spring tension back on this because you can see there's pretty much nothing there so sooner or later there's going to be dial slippage so this here should you know be pulled out like so so there's continual tension on it this is pretty much at its end it's not stretched so that can be taken care of at this end right here so that's something that could be addressed pointers pretty nice depending on who's purchased this sometimes they don't want the actual dial face repainted so that might just be like that for a reason the top side of the chassis could be cleaned a little bit nicer that's for sure the antenna itself is in very nice condition on the back side you see that so and it's not coming off it looks like that the original tar light glue that they use is still holding so now the truth that's definitely been worked on definitely been worked on here i'll zoom in on this so lots of you know 47 microfarad capacitors kmg i would have to look into this to see whether these are legit you united chemicon style capacitors or not so usually can be told by the vent stamp there's a resistor down here that looks like the coating is missing let's see here zoom on into that a little bit looks like the coating has gone off of that so that's a good candidate for replacement down there just a nichrome wire style resistor there's lots of roundies in here that always need to be checked i would imagine they have been checked because some resistors have been replaced see one here and one down there you see all the caps have been replaced so that's always a good thing so metal oxide resistor been added here 220k 150 ohm resistor it looks like it may have been replaced a bunch of resistors up here in the corner so they look pretty nice actually lots of roundies so for all of you that have been watching my channel for a long period of time see if that is there you'll know that a roundy is like i guess you could call it like an early style of the allen bradley uh carbon composition style resistor so basically it's a carbon plug so these aren't to be confused with carbon film resistors so this is a carbon composition there's a carbon plug in the center and then the leads go into a carbon plug and um what happens is the bodies on the roundies are is a porous style of of body and any type of if this has been in say somebody's attic or if it's been in a moist garage or something like that these things are are very susceptible to moisture aggression and what happens is the values they drift so the newer style they're squared off on the ends and they have kind of a shiny body that's the newer allen bradley style they're usually very stable they have to be subject to a really rough environment to make those move around or you know the circuitry surrounding has uh really put a lot of um a lot of i guess could say uh stress on the component to make the value move okay whenever you see resistors like their capacitors like this you got to be very careful with these you don't want to replace these uh if they're not moving uh these capacitors here a lot of the time are in rf and oscillator circuits and if you were to say put a you know a capacitor standard disk like a you know z5v or something like that uh you would be creating a very drifty radio it wouldn't stay on frequency so capacitors like this are very important this is a mica capacitor you can use an np0 c0g style capacitor uh in replacements here as long as the you know the voltages are correct uh but usually these never fail this type of ceramic like a ceramic tube style capacitor they're usually good and they last you know a whole very long time i very rarely see that you know these fail at all now you need to be kind of careful with these in some of the european radios some of their resistors look just like this so they look just like what we normally see over here as a capacitor they look they're an actual resistor i've pointed this out in some of my earlier restoration videos and if you're up to date watching my restoration videos you would have seen me point that out here's another capacitor down here something to always keep in mind another capacitor right there that is not a resistor that is definitely a capacitor so the uh the capacitors that have been installed are actually very nice 275 volt ac rated cap and um and it's an x2 rating so that's not too bad 250 volt ac so x y rated capacitors are always good for a line bypass that's a safety thing so has uh that's another thing that uh goes to the line chord now a lot of the a lot of the times when radios like this are restored and you put in a polarized line cord you'll notice that they break the neutral side so the hot style a hot side of the line cord stays constant and they actually put the switch in the neutral side so for safety reasons i upgrade that so i'll put an actual absolute value line fuse in here and i'll rewire this so that the switch breaks the hot side so that the neutral is always closest to the chassis because if you break the neutral side the chassis will elevate so we'll take a look at this here in a moment we'll see if this one is like that without me having to ohm out all of the line cord we'll see if this one is still like that so that's a modification that i always like to do just to be very very safe so i always do that we can also take a look at some of the resistors in here to see how how they've held up over time to see how far out of tolerance they actually are so i'll get a little bit of test equipment here and take a look at some of the more fine stuff all in all so far this isn't looking too bad it's not looking too bad at all uh there is some things that i i kind of frown on get the light in here a little bit closer i can see what's happened is they've cut some of the tabs and they've just elevated the tab there's actually nothing holding this so it's floating in midair basically the tension of the wire is holding this and they've tacked the capacitor to this so this is very common with a lot of techs what they'll do is they'll trim a lead off the capacitor and use it as a binding post but they let it float so usually what i'll end up doing is i'll install some form of a standoff down here something to hold that rigid so that this won't move around the vents of the capacitor are pointing right at the bottom of the radio so that is okay you'll see that the factory capacitor here is also pointing right at the bottom of the radio right and i don't know if that has an actual vent hole in the bottom a lot of the times when these things vent they'll vent from around where the little stamp is so they have a stamp in the bottom of the capacitor usually a square or a half moon and a lot of the times if anything goes wrong they'll vent out of those or around the leg itself so having the vents pointed down as long as they're not pointing at any type of a flammable surface is okay uh if there is say it's a wooden radio a lot of the times in the old wooden radios what they used to do is you'll find a fibrous sheet on the bottom and yes that is a sheet of asbestos so a lot of the times they would have no bottom but just that sheet down there and that is to stop you know if any components were to excessively overheat or if a capacitor was to let go that you know what stops the you know the flames from hitting the wood really so in a case where there isn't that sheet or there isn't a metal bottom pan it's always a good idea to point the capacitors towards something metal so that if it does vent basically anything that does fall a secondary so what i like to do is i like to point the the vent of the capacitor itself at a metal surface so it will shoot at the metal surface and usually what that does is it's there's a secondary effect so if it shoots at the metal it has a a small amount of time to cool off as it's hitting that before it falls on anything rather than having this thing just shoot directly onto a wooden surface okay so that's something else to keep in mind that could make your radio just a little bit safer so as a kmg series of capacitor again whether these are real kmg series capacitors or whether they are a very good looking counterfeit is yet to be discovered i will look into that this capacitor right here is placed across the line when the radio is turned on this capacitor does not have ac line service ratings so this needs to be replaced so we can see the neutral line runs up to this point here all right because we have a polarized plug and this is of course the neutral line assuming that the wiring in the wall of the house that this is plugged into is wired correctly so this is attached to one end of the carbon track in the volume control here we can see that it runs to the capacitor down here to this tube socket lug from the tube socket lug through this wire back over here to the switch so when the switch is closed this capacitor is placed directly across the ac line this needs to be replaced with an appropriately rated ac line capacitor and they have the x and y ratings on them those capacitors are designed to fail in a safe manner this has none of those ratings this is just a dc rated capacitor 630 volts dc is what this is this is a standard poly capacitor so this capacitor needs to be replaced with an appropriate safety capacitor the radio is plugged into a standard wall outlet right now and i'm about to see if they're breaking the hotline or the neutral line again the neutral line should be as close to the chassis as possible and the hotline should be the the line that's broken there should also be an absolute value fuse installed in that line there is no absolute value fuse in here so that is something that i would install so the neutral line in a radial like this should never be fused and the hotline should be fused you never want the neutral line to ever go open in this again the chassis can elevate if that happens another thing to keep in mind when radios like this are worked on and testing is done an isolation transformer is a very good idea so these are transformerless sets so there is no isolation from the line to the actual chassis and in fact many of these older radios one portion or one side of the line cord is directly connected to the chassis it just depends on the design of the radio a lot of them are connected via a capacitor and a high value resistor as well so isolation transformers are a safety measure that should be considered when a chassis like this is worked on so this is where the line cord is coming in here so the black lead here is attached to the neutral line so if this is hot i should get 120 121 122 volts out of this and that's on the switch so congratulations previous technician you did your job right you broke the hotline so this is the other side of the switch it's off i'll turn the switch on and there we go so that's the correct thing to do again an absolute value fuse should be added in a case like this just in case anything ever goes wrong in the particular radio you know it's an extremely light value fuse and that's just an extra safety precaution that should be considered now a lot of the times people say well you know it's uh you know the tubes are in a series string and they don't really draw all that much current yes the cathode bonding wire and the filament in the tube can act as a somewhat of a fuse but it's always nice if something goes wrong to save the tubes and have a fuse go instead fuses are a lot cheaper than vacuum tubes let's check some of the resistance values in here as well that's one thing that we haven't done yet so let's check this one here so this should be 2.2 meg it's 2.4 not so bad remember we're not dealing with a semiconductor radio here so 2.2 2.4 it's not going to make very much of a difference a lot of the times if these have moved that amount in this period of time they're going to be pretty solid at that point understanding the actual functioning of this radio and you know what resistors are placed where will also tell you over time with experience yeah it's absolutely fine in that area changing this resistor out would make no difference okay so this is one mega ohm here 1.1 absolutely fine there's a 47k ohm resistor here see what this one's rated at 47.8 no problems i can see a 5.6 meg ohm resistor under here let's see what this one's rated at wow that's pretty close so again the technician before did his job that's looking really good you know there's no problems there whatsoever so i'm imagining the reason that these are in here is because you know the other ones have been replaced because they're way out of tolerance so let's see this one here just for the fun of it 156 150 no problems there whatsoever so most of the time these will not move they'll just open so this is a wire wound resistor so when you see resistors like this usually they're go or no go and uh you know if the resistance value is a little bit different than what it says a lot of the times they've just been wound like that so uh yeah wire wounds another thing to keep in mind is these particular types of resistors cannot be used in rf circuitry whatsoever because these are inductive so they have a coil of wire in them so technically it's a coil in here so if you're to use a resistor like this in an oscillator circuit the oscillator circuit would not be your friend so you need to be using resistors that are either carbon composition or carbon film you can use metal film and metal oxide resistors they're absolutely fine so no wire wound resistors in rf or oscillator circuits keep that in mind just for the fun of it let's see how well the if is aligned in this radio receiver i have my signal generator coupled in to this little inductor down here and this antenna is just laying on the inductor like this so i can couple this into the radio receiver loosely the radio itself is tuned to 1000 am or very close or one megahertz if you like and my signal generator is tuned to one megahertz as well so i'll turn on the tone just to show you this on the actual signal generator itself so that's coming out of the radio right so now what we want to do is we want to tune for basically maximum here so i'll put this under here and what i want to do is i want to tune for a maximum signal so i'm going to get rid of the tone so it makes things more stable here okay now i want to look for maximum amplitude and when i get this to maximum amplitude is where the if will be tuned so let's find out here you can see that's going down right so you can see the if is going to shift as we're doing that and watch the frequency up here so maximum amplitude is where it's going to be and that's right there so it's very very close so it should be 455. that's maximum amplitude right there so you have 448 449 in that area it's very close now if the if is off frequency a lot of the times that will just affect dial tracking if it's out a little bit not too big of a deal as long as it's peaked up at that frequency that it's off so this is very loosely coupled you'll see that i haven't actually clipped this to this because what it will do is it will drag the alignment off so there's enough amplitude there that i can just put my probe close to this and it will pick that up if i was to clip this directly to that again it's going to drag the last stage and it's going to cause issues so i don't want to do that so not bad the iaf is relatively close it could use peaking up at 455 kilohertz let's see how well the oscillator in this radio tracks with what's written on the dial here so there are two completely separate devices there is no interlock between the two so when the engineers designed this radio receiver they put a lot of time into making this oscillator section very accurate so that in a production run they could always make it align with the dial scale that they've created now there are alignment points inside this radio to make the dial scale calibrate correctly but that can be affected if some of the components in the oscillator section itself have been replaced and as you can see many of those have been replaced so let's see how well this tracks right now this is pointed at 900 kilohertz and if you take a look right above here i'll put a signal generator up here that signal generator is set to 900 kilohertz so this is 900 kilohertz right here it's modulated with a 600 cycle tone at 50 percent modulation and the output level is 50 millivolts and that's just driving this little coil back here which is loosely coupled to the antenna so i'll turn up the volume this is already on and as you can hear nothing is there alright so i should be hearing a tone right now so i'll move this up there's nothing there there's that tone so turn this down it's getting pretty loud and right there is about center so as you can see it's almost one complete bar out so we should be receiving that tone right here not down here so let's see what it is down here let's try 600 just for the fun of it okay so 600 kilohertz okay i'll turn this up and hear it anywhere along the dial so right now we're right at 600 kilohertz right about there is center frequency right there so as you can see we're actually into the other bar here so that's how far off the alignment is here now if we go to the other end of the dial we can see whether this has been compressed or whether it's been stretched and that will give us an idea of where the actual alignment capacitor has been placed so i'll talk about that a little bit more when we actually get into the alignment itself there's actually in in many radio receivers the plates in the capacitor when it's completely when the dial doesn't track correctly at all you can actually move some of the plates around to make it track a lot better as well again in a restoration we'll talk about that at that point so let's take a look and see if this is up at 1600 here so i'll put 1600 1600 kilohertz in here or 1.6 megahertz if you like let's go right up to the top of the dial okay turn this up there's nothing there there's nothing there's some loud radio stations so i put this here really close to the antenna so what's happening is it's actually above so if i get this right in the right spot you can hear how it's there don't want to overload anything see that so it's actually above so the dial scale has been stretched so it's down this way and it's up this way so technically it needs to be compressed so what that tells us is there's a very good chance that somebody has actually played with the alignment in here and there's also a very good chance that that's due to somebody changing the components as i've explained in many of my other videos many of the oscillator components in these older radios are hand selected so what they'll do is they'll buy a lot of capacitors when i say a lot like a box a lot of a whole bunch of them and what they'll do is they'll look for certain values out of that lot in order to make their dial scale track correctly so a lot of the times when they design these things they design these things sometimes they will work out to you know perfect values but on the production line they'll find that maybe it's instead of being 10 pico for ad it's 12.2 that makes it a line a little bit better so what they'll do is they'll have somebody grading components and putting components that will say 10 picofarad on them but they're actually about 12.2 and that's why i absolutely always tell people if you're working on an oscillator section in an older radio one like this that has mica capacitors in them don't touch them if they work and they're not leaking and if you read those capacitors a lot of the times you'll find that their values are a little out from what they say yet the dial tracks perfectly and there's your answer with hand selecting components now i've covered this in other videos as well if you're interested in learning more about this kind of stuff there's i have a lot of videos here on youtube and of course i teach an electronics course on patreon i talk a lot more about this up there as well so now this makes me question at this point right every radio and everything tells a story this makes me question is the iaf section actually aligned in this or was it left alone it's off frequency just a little bit so that might be due to changing components and moving things around in there it may have received okay so it was just left alone so that might still be a factory alignment and that's the reason it's out just a touch because this dial scale is miles off it's really it is miles out so the only way to really tell that is to look in the tops of those transformers the if transformers and see how well the if transformers themselves have been treated a lot of the times you can see if they're heavily screwdrivered or sometimes they look like they've been completely left alone so again every circuit tells a story so what do you think do you think we should go through this and restore it again you can leave your comments below and i hope you enjoyed 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 and if you'd like to be notified as soon as i post a new video don't forget to tap that 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: 68,595

Keywords: Restoration video's, radio restoration, Mr Carlson's videos, test equipment restoration, receiver restoration, tube radio repair, vacuum tube equipment, electronic restorations, restore old radios, learn electronics, understand electronics, fix electronics, test electronic circuits, repair circuits, fix circuits, radio repair, receiver repair, circuit diagnosis

Id: ow3IeZVQbKk

Length: 39min 4sec (2344 seconds)

Published: Wed Oct 13 2021