Getting Rid Of Distortion In A 1931 Atwater Kent Radio

Ladies and gentlemen, welcome back to Amateur Repair Time. I have been doing this huge series way too long. I know there's been too many videos, people, and some of them have been too long because I talk too much, but I've been working on this Atwater-Kent Model 72 radio from 1931, and we're getting down to the finish line on it. We're not quite there, but we're making some progress. So, if you haven't been watching the series, I'll give you a breakdown of what we've done. This is the cabinet. It has a Model H receiver in it that's actually turned on right now. And we did one video where we just took it apart and checked out what we had. We did another video where we went through all of the sardine can capacitors inside of the machine. So, there are these little sardine cans. You're going to see all about it here shortly. Underneath the chassis that have three or four caps in all of them, and we replaced all of those. It's all your bypass caps and things like that. When I got done with that, I was reading online on some of the forums, and people were saying that on Atwater-Kent, you don't necessarily have to replace the capacitors. Now, I know that sounds crazy. I know if you're a radio guy, you go, oh, come on. The thought process behind that is that the Atwater-Kent capacitors were very high quality. They were sealed in these canisters. This can right here is the power filter capacitors. None of them are electrolytic. They were all paper. Well, not paper, but I guess you'd call it paper. We did a whole video on it before when we tore them all apart. And so, a lot of the Atwater-Kent guys, they don't replace the capacitors on certain models. Now, if it's got electrolytics in it, they replace that, but none of these are. But, you know, we haven't worked on one of these before. So, I went through, I replaced everyone. It took quite a while because they're in these little metal cans that you have to get open, and then you have to dig the caps out, and then you have to put new ones in to the right place. Anyway, so with that said, we did that. So then I did a video where we did work on the filter capacitors, and we did the same thing. It was this big block, about like that almost, and we took it apart, got the old junk out, and put brand new ones in it, which is all represented here. And then, we've done so many on this. I did one where I checked out the power transformer to see what was going on with it, where it came from, and rerouted some of the wires because that's not the original power transformer. And they had some wires kind of hacked in and taped, and we fixed up a bunch of that. There were some deteriorated wires. We took care of that. I think that's video four, if we're keeping track. I may have them out of order as well. We did a video where we checked all the voltages on things, and we worked on the front of this radio. So the volume control, the tone control knob, and then we had to work on the actual, the way the tuning knob interacts with the tuning capacitor. So we did that. We did a video where we tested all of the tubes. Okay, so we did that. We did a video where we, I don't even remember all the stuff we did, where we aligned it. We did all kinds of stuff. So anyway, this is like video 11, I think, of this series, but we're getting somewhere. On the last video, we aligned it. We got the thing to work. We got pretty good reception. I've just got an antenna hooked up to it, which is literally a speaker wire that's ran down the hallway. And it got pretty good reception, but it's very distorted. Oh, I did a video where we repaired a speaker. So this is a pretty good condition speaker from 1931. It's their model N speaker. It hangs in the cabinet on these two little hooks here. And this is the one that was in another one. This one was all screwed up. It had holes and rips all in it. So I took coffee filters and glue and paint and repaired the cone. And after I did that, we ended up with this speaker, which seems to be actually working. However, at the end of our last video, after we aligned it, we discovered that everything was kind of distorted. It just had this kind of crackly sound. And I thought, well, maybe it's the speaker. So we tried the other speaker and it's the same thing. This speaker has kind of a buzz in it because there must be some dirt in there or something. So anyway, that's where we left off last time. So we need to try to get it to sound better. And then we need to refinish at least part of the cabinet. That's kind of what's left on this Atwater Kent model 72 journey. Also, I just want to point out that this is amateur repair time. I don't know what I'm doing. I'm just trying to figure it out as I go along. I have worked on several radios and, you know, repaired some, recapped some. I work on all kinds of things and I enjoy vintage electronics, old record players, radios, clocks, as you just heard down the hallway, things like that. And on my other channel, Joe's Video Games, we do arcade game repair, pinball repair, which I've done for a long time, jukebox repair, things like that. So I know a little bit about it, but these tube radios are just foreign to me. I've only done, this might be the fifth or sixth one that I've done, right? And I've never done one this complicated. I did do this silver tone over here. Got it pretty good. I did a majestic Grigsby Grunno that turned out pretty good. Okay. So all that to say, we need to figure out why this thing is distorted. So at the end of the previous video, I said that I was going to go through and start substituting in tubes one at a time, just to make sure we didn't have a tube causing the problems. So I have been doing that. I substituted in different 40 and I'm doing them one at a time. So I substituted in a 45. These are the two 45 outputs. I substituted one in, didn't change anything. It's made a volume a little higher or lower. Took it out, put the original one back in and then substituted the other 45. Same thing, didn't change anything. And then I did the 27. So we've got the oscillator here and there's one back there, one there. Did them one at a time. And then if they were fine, like if there was no change, I put the old one back where it was because I don't want to throw the alignment off too much by doing this because we already aligned it. And then I got around to the 24s and I was messing with the 24s. And so I've got this one and I swapped it and I found a bad tube that I was swapping in on the 24s. This one isn't any good. So I'm messing through it and I start noticing that when I turn the tone control, I get kind of a different sound, which you should on a tone control, but the distortion changes a little bit. And I thought, huh, that's interesting. So I don't really understand how these work. Again, I didn't go to school for this or anything, but here is the tone control, or let me find where the tone control is. Here is the tone control. And so it's a very simple little thing. We cleaned this up before, but you can see what it's doing. There is a tube here and a tube here. Oh, you know, it's the two output 45s. And there is a resistor. It was a wire that's 5,500 ohms. They're writing it a little strange, but 5,500 ohms. And it comes up to the selector of the tone control. Now, the way the tone control works, we cleaned it all up. You are selecting one of these four capacitors. And that's probably pretty common on these tube radios. So it's either a 0.01, a 0.004, a 0.002, or a 0.001. So that capacitance value is going to change the tone of the radio. But if you look, what it's doing is it's placing a resistor and a capacitor across the two 45s. So I've been doing a lot of research on this, just trying to learn more about Atwaterkens and things. And so there's an Atwaterkens forum online on Facebook. There's web pages. This thing was made in 1931. For almost 100 years, people have been trying to fix these lovely radios. I mean, they really are a nice radio. And I was searching distortion, Atwaterkens distortion. And I kept coming across a couple things. One of the things that I kept coming across was people saying, well, these older radios just have a little bit more distortion than you're used to inherent in them. They just, they sound a little distorted. And I can't remember why they said that, but there's something about the design. One of you that knows what you're talking, what you're doing can probably tell, but there's something about the design of the radio that lends itself to distortion. And at some point they corrected that and stopped making radios with that problem. So this is the schematic you can decide for yourself. There is a shield on four of the tubes, right? So I kept running into that, them talking about, well, you're going to have a little distortion on these. And then I heard a couple of people say, mine's pretty clean. Mine sounds pretty decent. And Atwaterkens made a bunch of radios around this time. So there's a ton of them, a ton of different models and stuff. And then the other thing that I kept running into was people talking about the quality cap. I think that's what they called it. We'll look it up here in a second because I'm interested in it now. The quality cap. And they were saying that in some of the Atwaterkens sets, this cap was buried in, I think in the choke canister or something, like where these are, it's buried in there. Now it's not on this one. And so I was thinking, well, I don't have a quality cap on mine. I don't have to worry about that. And they were talking about some of the older sets. This is 1931. This is Atwaterkens. I think it's their first Superhet set. And before that, it was more of the older style, but they were talking about some of those older ones and they were saying, oh, you got to change that quality cap. And some people were saying, well, what happens if you don't? And I said, well, if you, it's across the output transformer and it, you will get a muddled, distorted sound if that quality cap's still in there. So people commonly, what they do is they just cut the thing out. They just, because it's, they can't dig it out very easily because it's buried in one of the canisters. So they just cut a wire coming out of the canister. And if it kills the set, that was one of the power wires. And if it doesn't kill the set and the treble comes back on the sound, they found the quality cap and it doesn't need it. Right? So I started thinking, well, huh, we got, we're going to go research here in a minute, but I was thinking, well, that's kind of like the quality cap right there. It's a tone cap on the output of the, on the secondary of the output transformer. Right? And so I took that little piece of cardboard and I put it underneath one of the blades of the tone control, which basically is just severing as if I had cut that 5,500 Ohm wire and that capacitor that are attached between the two output tubes. And I got to say, it sounds a heck of a lot better. Right? So let's see if we can get it back on station here. Now, another thing I will mention just quickly, notice there's no speaker hum right now. You can hear transformer hum, but there's no speaker hum. I had speaker hum before that I couldn't get rid of. Even if I turn the volume all the way down, you just hear that the whole time. It doesn't seem to be doing it as much now. That's the volume way up. I've got this volume control. It doesn't go to zero. This volume control goes from five to 15. It doesn't go from zero to 10. Okay. So there's no speaker hum. Okay. So we're just off channel. There is a huge clear channel at 1,100, four miles from here. Okay. That's a 1931 radio with a glued together speaker in it that I have just disabled the tone control on. So why would I be having that problem? Well, if you watch the whole series, you may remember I didn't rebuild the tone caps. And I said at the time, well, we'll skip those because they're easier to get to. The can is right there. We'll skip those. And then that'll give us a test of whether or not you can just leave the Atwater Kent caps alone. Well, guess what? No, you cannot leave the Atwater Kent caps alone. You might get away with it on the filter caps, although that would be the most dangerous thing to have crappy. But those sardine cans, you really need to replace because I'm having all kinds of trouble out of the tone caps that I purposely left undone just to test it. So yeah. Okay. So let me go see if I can find some information about that quality cap, if that's what they called it. And maybe we'll read a couple of people's opinions on that. And maybe that'll tell us something. Okay. So I've been reading about it. This is the model 55, which is several years earlier set, and it's not a super head, but this is their quality condenser. Our condenser is right. Our tone control is right here. They've just put the quality condenser on this earlier one just after the output tubes. So we're in the same ballpark is what I'm saying. So if this is such a problem on theirs, I would imagine that these tone control ones are probably my problem on this one. And they said that the purpose of this quality condenser is to take the top off of the treble. I guess the early sets had a lot in the horns. And so they put a condenser in there. So that would go, that's my layman's explanation. So, you know, we've got the tone control where we can select four different tones. So right now it's completely disconnected, which probably makes it sound worse than it would sound if it was proper with the proper caps. So my whole point is, I think all four of those caps are bad. We need to take that canister out and restuff it. Now, what we could do is just rig up a... I could disconnect the wires to it and just rig up a cap across two of the wires. And then that would tell me for sure, you know, we ought to be able to get a good tone out of that. So I took out a bunch of screws and the control moms and I was able to get this loose. So I could lean it forward and take the bracket off. And here is our sardine can, the last one, the elusive one that was hiding under the front plate. So I labeled it one, two, three, four, five. You know, I have the luxury of, I don't have to take photos of my stuff because I'm taking videos of my stuff. So what's in here? Well, there's a label on it. 2B6. And Atwater Kent actually kept very excellent records. So I believe I can get a perfect, you know, it said it on the schematics what they were, but I think I can find a perfect schematic that shows exactly how these are laid out inside. So the way I did them before I did all the ones underneath, there were about five or six of them, was I heated this up and was able to pry the metal out, but I've got a torch now. So I'm going to heat it up with the torch and let the solder and the, all of the wax inside drip out into a pan or something. And then once I do that, I can get that plate off pretty cleanly and we can look inside it and see the capacitors. But let me go find the schematic for this. B2B6 it looks like. Atwater Kent Radio, electrical values of resistors and condensers in all receivers, 1924 to 1932 inclusive. Okay. And it just shows you every freaking thing. And right here on the very first, second page, I guess it says tone control condensers, which is what we're looking at. And remember ours said B6. So it's kind of hard to make it out, but I can tell by the schematics as well, you know, what those values are. The ground is the bottom left there. And then all of the grounds are tied together of the four capacitors. And one lead is here and the other three leads are here. And I can tell the values by looking at the schematic. The top left one is 0.001. And then these are a little muddied, but I should be able to figure that out by looking at the schematics. So, and that is looking at the back of it where the plate is. Nope, I got that wrong. That must be looking at it from the front. So looking at it from the front, that's where the connections are because the three on the top, I can't do it any other way. So it's gotta be like that. So it's all kind of reversed from how that is if you're looking at the back, but we'll figure all that out. Okay. So the system I came up with, well, I didn't come up with it, but that I decided on was you take the can, you take the sardine can, you get a little torch or a big torch if you prefer. And you hold the thing up with a pair of pliers and you just heat the crap out of it until all the solder drips off. And when the solder drips off, that plate will fall off if you tap it. And then now we have a can that has most of the wax or whatever is in it dripped out and we are down to the actual capacitors. We can remove those and then stuff our new ones in there. Easy peasy. Okay. So here's the plate. Nice and clean. You see it's burned though from the torch. We'll clean that back up. And then this that we were just looking at is just a spacer. It's literally just some little pieces of card. It's kind of like cardboard, like baseball cards, just taped together to fill up the rest of the can. And then down inside, that is the actual capacitor. So you see, it's got two leads coming out the bottom and three leads coming out the top. So they're paper capacitors, but they're sealed up in this can. So my thought was, well, maybe they're all right, but someone was mentioning, you know, they still leak, even if they're... A lot of the problems that capacitors get has to do with moisture and things like that. So these wouldn't have the moisture problem, but they still, there's like an acid in the paste that's in them that causes problems and makes the capacitors drift. So we think that's probably why we've got such a crappy sound, right? So if I suck the solder off of here, the pins of that capacitor will pull right out of those holes and we'll be completely fresh where we can put a new capacitor in there. All right, so here is the cap that came out, 100 years old. It says November or something underneath that paper. We looked at some of the other ones and they were all dated 31, I believe, which tracks with that supposedly when this was made. So on that schematic, it is showing it like this, okay? And so the ground is here and 0.01 is here. So the ground is there, 0.01 is there. And then this is 0.001, this is 0.002, and this is 0.004. Now, it seems like if those values are off a little bit, it's just going to slightly change how much of the highs are cut out of the sound, you know? So you don't have to go kill yourself trying to find the exact number from antiquity. And again, it's all reversed if we're looking at the back. So 0.001, 0.0022, and 0.0047. Because they don't really make a 0.004 anymore, and they don't really make a 0.002 anymore either. And so I've also soldered them to the ground lead that's coming out. And I've got all of that tucked down in there low so that I can solder the back on it. I guess you could leave that off, but I put all mine back on. And this one's going to be a little easier because I didn't have to bend the plate or anything because I just melded all the solder and it fell off. So it ought to fall right back in there. So it's pouring, it's raining tonight, so the weather is not good for reception, especially since I've just got an antenna rigged up. But we are pulling in some stations. And the distortion is gone. I don't even have it on the highest tone. When I took this apart, I had to remove the pointer and put it back. And I think I've got it not quite how they had it, so it doesn't completely line up the way we had it aligned. I've also got one of these grid caps that's broke, so I need to order one of those. The grid connector, I should say. But I don't have any clear reception on anything where I can show you that it's clear. Let me see if I can get maybe a vocal. So I think it's performing as expected now. I've read a lot of people online talking about them, and they said, yeah, it's going to be a little more distorted than you're used to on a more modern superhead. So that's probably about as good as one will sound, this old. I would love to get a music channel. Ah, I wish the reception was a little better. Let me swap to the better speaker while we've got a song playing. So it's a little louder than the repaired one. This one has a little static in it, too. I think there's some dust or dirt. And the volume on these is crazy. I'm all the way down right now, that's as low as it'll go on a weak channel. If I put it on the local clear channel, it's so overblown you can't even listen to it. It's so loud. There's no AVC. It'll be interesting if I get a content strike for that. Oh, it's Zoomer. Yeah, I think it sounds all right for what it is, and with no good reception tonight. So we need to remember this channel. Looks like it's like 7.30 or 7.40. Guys, I'm going to switch this song back to the repaired speaker that doesn't buzz. All right, I think that's acceptable. All right, yeah, so I think that's acceptable. I need to get a grid connector to replace the one that's the broken half, and I need to do some work on this cabinet. The cabinet's pretty rough. I am not a cabinet refinisher, but I'm gonna give it a good shot. Basically, the top is rough. It has a really bad, you know, so we got to do something about that. So I'm just going to sand it down, and I'm going to use toner on it. So we'll see how that ends up. So I hope you enjoyed it, folks. I think I've about got the thing as close as I can get it to working properly. I think I learned a lot so far, and next week I'll learn a little bit about cabinet refinishing. Have a good evening.