1951 Radio Receiver - Can We Bring It Back To Life?

hi everyone and welcome to another episode of mr carlson's lab let's get started here's a neat looking old radio from around 1951 it's a general electric model 404. looks really nice they've done some really nice work in the plastic here i think this is called a mahogany type finish so very nice looking old radio so this has been on my shelf for some time as you can see all the dust haven't wiped the dust off or anything just handling it and moving it around you can see some of it is wiped off so do you think this thing is going to work or do you think it's going to make smoke so i know as much as you do at this point let's plug this thing in and find out so place your bets what do you think's gonna happen so i'm gonna plug this into a current limited isolation transformer and variac supply i guess i should make sure that the thing is in the off position okay it is all right so plug this in no smoke so far so the current limited isolation transformer and variac supply will current limit out if anything really majorly is wrong with this thing so that's the reason i have that there i'll turn this on switch is nice and positive kind of uh the actual volume shaft is a little loose and see if i can see any action in the boat i do see something in there glowing so that's a good sign it's still silent though let's sit for a moment well there's a bit of hum there it's coming to life there's a little bit more than a little bit of hum there okay there's a ton of hum there the whole case is vibrating okay so already we're starting the troubleshooting procedure so what's happening right now okay so we know that the audio output tube is working we know that the rectifier is working and we know that all the tubes are lighting up if one of the tubes was burnt out then we wouldn't get anything all right so all the tubes in this are lit up so now let's see if the volume changes anything i hear a difference hear that so we do have amplification going on so next thing is i'll move the tuning around let's see if we can kind of hear a station in there or anything that is very loud so you can see that we're actually it's trying to receive a station but of course you know the hum is so loud you can hear it kind of just mixing and making all sorts of interesting noises so just from this test we've verified that the audio output tube is working it's obviously strong the whole case is vibrating we know that we can change the volume by moving the volume control so there is amplification happening we know that the rectifier is working in here because it's humming we can there's obviously b plus and we know that all the vacuum tubes are lighting up inside this thing because if one of the tubes is burnt out this is like an old christmas tree set that's the way that the tubes are in here if one of the light bulbs burns out none of them light up right it's the same thing with one of the tube filaments if one of the tube filaments in this radio burns out none of them light up and we don't get anything so we've already diagnosed so much inside this radio just with this one test now it's never a good idea to purchase a radio like this and plug it directly into a wall right away because there is no current limiting happening so the current that's supplied to this thing through the line cord right now is through an isolation transformer and it is current limited so if anything was to majorly go wrong there would be no more damage happening to this radio that's why i can do this so just a word of caution if you like these older radios and you purchase one of these things and you want to just plug it in refrain from doing that or if you get the thing repaired it's going to end up costing you more money because you can damage tubes and many more components inside this thing of course it's not safe to do that as well right all right so we know the thing somewhat works so yeah it's kind of in the middle somewhere so what does this do well this gives us something to troubleshoot together so let's open this thing up and let's just replace the components that are needed to make this thing come back to life again and then down the road we'll end up restoring this whole thing together as well so we'll get a couple videos out of this thing should be a lot of fun so i'll get some tools and let's diagnose this thing together and find out why it's doing this and i see what we need to replace to make it work decent again all right let's open this thing up so the first thing i want to do is pull the knobs off of this thing wow those are on there well that is on there tight all right nice you know decent solid plastic doesn't look like it's cracked or decaying at all noisy really hard plastic sounds like i'm just slamming these against the bench but they're just touching the bench and they make a lot of noise all right so on the bottom yeah quarter inch here they're not all that incredibly tight there okay so this will probably just slide out now so let's hold this here let's see if i can just slide this out it's coming out oh it's filthy and it's being held by the speaker leads in there there's a metal bottom sliding around in there as well those little speaker leads right here so i'm going to no it looks like they're just stuck on there so i don't think i have to desolder them it's kind of nice all right i'm in awesome nice metal bottom you don't see that very often in these radios so that off to the side inside it's looking really nice a speaker looks fantastic out of the way one two three four five six six tubes set fancy stuff all right taking a closer look at the bottom portion of the radio do you want to take a guess at how many components have been replaced in this radio over time if you want to take a counter take a closer look and then take a guess pause the video now and do your account and try and spot as many odd components as you can and when you unpause the video i'll explain what's been replaced over time all right so we first saw this one here looked like it had been replaced that one stuck out like a sore thumb and so does this one right here so this con bro capacitor is definitely not original i see an electrolytic capacitor down here that's been added over time i see right under the audio output transformer you can see this red writing on this darker colored capacitor down here that is a sprague capacitor with red writing the red writing indicates that it's a dye film capacitor it's not a paper and foil capacitor if this was paper and foil the writing would be yellow so these are a relatively low leakage style capacitor so still a pretty decent capacitor if you find these things in pieces of equipment that's nothing to really fear nothing like these things these things are horrible i'll explain that in a moment so what else do you see that might have been replaced in here well if we look at this capacitor the main filter capacitor this is in this little clip and it fits quite nicely but what's odd about this look at this thing here this is designed to be screwed to a chassis so unless they installed this capacitor here and just left this clip on which i really can't see them doing because this can slide around over time and slide into circuitry and cause you know short circuits and things like that see if it's loose sometimes they are oh it is that's very loose so chances are this has been replaced over time and the technician that put this in here didn't end up taking this clip off they just left it here which is really silly because again this can just slide around and short out things in here so chances are this has been replaced as well and all the rest of it looks like it could be relatively original so these are the original wax capacitors these will definitely all be faulty by now so in a restoration these would all need to get replaced and of course all the resistance values would need to be checked and everything like that as well but in this video here what we're going to do is we're just going to get this thing working so we can see how well it works it's just the minimal amount of components replaced so what do you think in here would need to be replaced to make this radio come back to life again well we know this radio is humming extremely loud and what component in here or components will take that loud hum away well that would be a filter capacitor and the filter capacitor is this device right here so what i'm going to end up doing is i will get a tester and let's just test this filter capacitor and let's see how much capacitance there is if we take a look here we can see that it's rated 50 micro farad and 50 micro farad so there's two parts inside this capacitor so we have a common lead here which are a negative lead which is this black here so it's common between the two capacitors and then we have a red lead here and a red lead here so this this lead here to this lead here will be 50 micro farad and this lead to this lead will be 50 micro farad so what we'll do is we'll end up attaching a tester here and going to this lead into this lead and let's just see what ends up happening i'll go get that tester and i'll be right back before i go about attaching my meter into circuit here and testing to see if this capacitor is okay i'll explain more about testing these capacitors in circuit in a moment i definitely want to make sure that this capacitor has no charge on it because if there is a charge on this and i have this in the capacitance setting i can damage the meter and i definitely don't want to do that and that goes for any capacitance meter if there's a charge left on the capacitor you can destroy your meter so you need to always make sure that the capacitors are safely discharged not only for your meter safety but for your safety as well now this is completely disconnected from the ac in line and everything has been off for quite a while and to tell you the truth i'm pretty sure that this capacitor is bad but you know what you can never be too safe so what i'm going to do is i'm just going to make sure that that capacitor is safely discharged now this is a capacitor discharge device that i've designed and released on patreon and it safely discharges capacitors there's two red leds on the top here if one of these leds glows depending on the polarity right if one of them glows there's still a charge on there when the led goes out the circuitry inside this box has safely discharged that capacitor there's also carry through leads on this box as well so you can have a an external dmm off to the side that will read as well so you can actually watch the numbers fall if you don't want to rely on the leds alone so what i'm going to do is i'm going to attach the test leads across one portion of this capacitor right now and keep an eye on those red leds if you see one of those red leds glow you'll know that there is a charge on this cap so here we go and there's nothing there okay so i'll go over to the other section of this capacitor keep an eye on the leds and there is nothing there so i kind of figured that but you know what again you can never be too safe so move that out of the way so what i'll do is i'll put this onto like a pass in a setting turn on the back light to get rid of some of the glare now in order to test an electrolytic capacitor in most cases the lead of the capacitor you can leave the common in circuit but the actual capacitor leads the positive lead should be removed from circuit in order to get an accurate reading because resistance in the circuit itself can cause you know basically a false reading on your capacitor tester so here's a little trick if the capacitor is going to be open or close to open the meter will read low now we figure that this is most likely going to be open right because it's humming so there's basically no capacitance there if the meter reads very high so it goes into ol or say it in this case the programmers of this meter had a sense of humor here i'll show you if i hold these leads together for a second you'll see it'll say ouch so they had a sense of humor so instead of saying oh well it says ouch but at any rate if it says ouch that means that it's basically it's taking too long to charge and it's beyond a limit and if it's beyond that limit that means that this capacitor may be good so in order to verify that i will have to remove one of the leads so i can do this quickly first and this will just you know tell me if it's open or not which i kind of suspect it is okay so i'll attach this here and we'll test one capacitor here let's see what the meter says so we're just over half of one microfarad and this is supposed to be 50 microfarad so what does that tell you one section of the filter is open let's take a look at the other section of the filter here so i'll put this lead over here and again we're just just over half of one microfarad and they're supposed to be 50 and 50. so i didn't even need to move the capacitor out of circuit to test this a nice little shortcut when you suspect a capacitor like this is open again if this red high if the if the reading was high on here i would have to open a lead to verify this so what i'm going to do is i'm just going to tack in two 47 micro farad capacitors across this one here and we'll see if that eliminates the hum and we'll see if we can get any radio stations now in a case where you're about to restore or repair radio like this you can never leave the old capacitor in circuit because the capacitor can short circuit at any time you can never do that the old cap always always always always has to be removed but in this case we're just doing a bit of troubleshooting and trying to just get the thing going so i'm just going to tack two into circuit and let's see what happens we'll see if we can actually receive any radio stations with just the filter capacitor replaced all right i grabbed two capacitors out of the bin here and i will just put these in a circuit tack them into circuit like so that should hold and i'll tack this down here i'll bend this forward switch hands and run that in a circuit like so no problems and i will attack this one over here so i'm going to add some solder to this one here it doesn't look there's a whole lot of solder on that terminal which will make things a little bit difficult so i'll add some solder here and i will put this here like so now what i'm going to do is just take a piece of junk wire and run the negative back over to this area right here so i'll just have this out like so from the other radio when i cut that antenna lead off i still have this around here so i'm just going to strip a piece of wire here and that should hold up that should hold up for now so what i'll do is i will a little bit of solder on this so that it solders much easier when i put this in the circuit like so add this down into here all right and then there's this end that i need to do as well hopefully that'll stay somewhere where i can solder it okay so it wants to go right on top of that capacitor look it's aiming for it wants to go there all right just stay look at that it's gonna be difficult okay so i'll hold the shoulder with this hand and i'll do this all right yeah a bit of soldier to the lead of the capacitor look at that just wants to aim right for it how often does that happen it's like winning the lottery usually the wires want to go everywhere except the place where you want to solder them okay so that's looking pretty good okay so let's put this here have that there like so and bend that over there that out of the way and i will turn this the other way around and let's see what happens i guess i'm going to need to attach that speaker from here as well and i'm going to probably need some jumper clips to take these wires over to the speaker cabinet over here so i'll be back in just a moment i'm going to have to grab some alligator clips and run that over to this other cabinet i have the two speaker leads attached right now so what do you think is going to happen i'll plug this back into my current limited isolation transformer variac supply turn that on and i'll turn some of the lights off here so we can maybe see some of the tubes glow turn this on so that's obviously what we were seeing through the back is the lamp for the dial there the tubes are starting to glow now this is a six tube set so it has a pre-amplifier stage the reception in the lab is pretty bad without the three six nine antenna attached to anything so hopefully this will receive something if it even does come to life these out of the way and warm up it's coming to life there's radio stations i got vr is horrible so it is receiving it is working so just those two capacitors have brought this thing to life and it's actually receiving not bad for no external antenna it's just this antenna right here in the lab and as i've said before there is very little reception in here so it's doing incredibly well with just the two filter capacitors if i was to couple in the 369 antenna i'm sure the entire band would be full of radio stations with just those two parts replaced so this should make a very nice restoration so that's all it took so far and it's actually working very acceptable so i'll just turn this off actually you know what i'll give it full line voltage that one there wrong switch and we'll see what happens see if that increases the sensitivity even more let's try that maybe definitely helping wow oh some pretty strange radio programs on during the day so anyways it's working very well just shut everything off here again very few components replaced and it came right back to life now don't think that repairs can be done this easy in order for this thing to be reliable all of those wax capacitors on the underside so let's turn the lamp back on up here so all of these need to go and all the other values need to be verified as well in order to make this you know very dependable and of course work the best that it can so with just those two filters the thing just came right back to life not too bad this will make a wonderful restoration so hope you enjoyed this troubleshooting procedure if you're enjoying my videos you can let me know by giving me a big thumbs up and hang around there'll be 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'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 show more tab below the video's description 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 all right until next time take care bye for now

Channel: Mr Carlson's Lab

Views: 39,783

Keywords: GE Radio Model 404, Mr Carlson's Lab Videos, radio receiver restorations, radio receiver repair, electronic circuit repair, learn electronics, restoration how to, repair how to, test equipment restoration, test equipment repair, restoration videos, electronic engineering, electrical engineering, valve radio repair, valve amplifier repair, tube amplifier repair, how to repair electronics, circuit design, repair videos

Id: SjMq34IrWf0

Length: 23min 50sec (1430 seconds)

Published: Sat Dec 11 2021