Canadian Marconi Model 160 Video #24 - IF Sweep Alignment, IF Trap

Ajouté : 2026-05-20

[00:00:01]Hello. Good morning. Thank you so much for joining me in my shop here. Today is May 19th, another day with threatening storms coming. We had big storms go through uh raintorms go through uh last night and I can tell from all the debris on my deck and it was a a pretty heavy storm even though I slept through it.

[00:00:21]And much worse storm coming later today including the possibility of tornadoes.

[00:00:26]And we are right in the center of the of the uh warning area if you like. So that's that's the deal today. And and sound you just heard now is my air conditioner coming on because the temperature is going to 27 today. It's very muggy. Yeah. Quite quite a change.

[00:00:44]And that happens here in Canada. You go from kind of cool spring weather to hot ugly summer weather like that. Okay. It doesn't mean it's going to stay hot though. Probably cool down. Now, what to do about this radio?

[00:01:02]Uh, that's a good question.

[00:01:06]Either I have to accept I'm defeated on the short wave band and the spurious oscillation or whatever it is that's going on there. Um, I'll be giving that a lot of thought and maybe we'll look at the schematic to start off with and just try to understand what exactly is going on there and then look for some parts in the circuit in particular. Um, this type of capacitor right right here.

[00:01:32]There's another one back in here.

[00:01:34]There's one up here. These are micica capacitors.

[00:01:38]Uh, generally they are highly reliable. There's another one right here. And I tend to just ignore them when I'm doing this work, unless there's good reason to think one of them is bad. Well, maybe the oscillation is a good reason to think one of them is bad. Even though I've got a pretty interesting sounding theory about the oscillation and putting in the uh cathode resistor and all that kind of stuff.

[00:02:06]Maybe maybe it's just a simple problem of a capacitor not doing its job. So, let's take a look at the schematic and see if we can conjure up anything from that.

[00:02:20]Okay, here is a version of the schematic. I'm saying a version because uh there is another one here. Watch what happens in this area out here.

[00:02:33]If you've been watching my videos, you know uh you know what happens. The sleeve goes on. Note shows up.

[00:02:40]H um so this is what led me to conclude that that the oscillation is something that was being struggled with by the designers of the of the radio. Now here's here's another schematic.

[00:02:53]Now in this schematic that's missing and even the sleeve is missing off this wire. So it was never here when this was drawn. Go over here we see this uh extensive note here wire legend it's called. But if we if we flip back to this schematic, that's gone. And it's been replaced by this uh socket bottom view now.

[00:03:18]Haven't gone looking down here too much.

[00:03:22]Uh okay. So, let's look at the schematic. We'll use this one. I'm sorry. My my rolling bar just doesn't uh what do you call that? Scroll bar.

[00:03:30]Scroll rolling thing. You know, you push with your finger. Doesn't work well.

[00:03:35]Okay.

[00:03:37]stuff not working everywhere everywhere you go. So the circuit involves this tube probably as the amplifier to generate the oscillation.

[00:03:47]Uh because of this action here, I'd have to think the problem was with this grid and not with the oscillator grid here.

[00:03:59]Um, the radio is in the note is missing here. The Let's go back to this other one. Read the note down here. Oh, there goes my scrolling bar. There. There's that image down here, which is up here on the other schematic. Here's this note. And it says, uh, wave change shown in extreme counterclockwise position. Short wave rate there. And that's true. So this is in a shortwave position.

[00:04:32]So that being the case that tells us this is the shortwave coil that there's a little node there. And if we come this way for the first time I realized there's actually a note here. Short wave, medium wave, and broadcast. I missed those earlier.

[00:04:47]So this is a shortwave oscillator lead.

[00:04:56]What what capacitor in any of this could somehow induce an oscillation because the capacitor is weak?

[00:05:08]Wow. Um the ones that were most likely have been replaced like like this one and this one.

[00:05:20]Uh um if I check this resistance what this is down in the local oscillator circuit though and it doesn't appear the oscillator circuit is the uh source of the oscillation only because of the note that appears on the other version of the schematics suggesting the problem is on this line.

[00:05:45]Another interesting question is where does a high DC voltage come from that I'm measuring? So, I I've been measuring um off the volume control, which which right here, this is where my voltmeter has been connected all the time. And so, we've been reading the voltage at this point, which is somewhat well, it's going to be I I know not necessarily. I was going to say it's depleted by this resistor, but not necessarily because essentially no current flow in this line.

[00:06:17]So the voltage here is the same as the voltage on the on the grid on the controlled grid.

[00:06:25]Uh we have this guy um which I uh put a little water in it. It developed a voltage. I don't know if it still does uh develop a voltage. We sort of left this um you know this is a temporary thing. The battery is going to go to zero and probably maybe it's already done that. I can't leave that in the radio.

[00:06:45]inclined to short this back out.

[00:06:50]That's a little interesting because now we have a bias cathode biasing resistor here.

[00:06:57]So getting rid of this will have a little bit of a different impact on this tube.

[00:07:04]You know that this cathode resistor thing um it's it's not only uh affecting the bias of this guy, it would be affecting the uh local oscillator too.

[00:07:14]But I don't want to bother forget about that. Um well, you know, there's nothing jumping out here. Hey, that capacitor that be the guy. Um and and and you know, replacing them willy-nilly.

[00:07:30]Not really the way to go, I don't think.

[00:07:35]So, we're going to leave it as it is for now. And uh I think maybe I'm going to turn my attention to to to doing a better alignment job on the radio. And when we get to the uh short wave band, maybe I can align away the problem that's that's occurring. Now, how would that work? How would that work? That that would if that were to work, then it would have to be this, you know, varying this trimmer.

[00:08:05]I don't know how that could possibly work.

[00:08:08]But let's now there's another possibility too up here that I've got the radio aligned uh on its image because I was unclear what the first time I did it. It was just unclear to me that I'd succeeded. So that's another issue. Uh could that prompt a spurious oscillation? I don't think so. In itself, I don't think so. But having the radio tuned wrong might, you know, might put it into the the long grass maybe. I don't know. instead of being on the fairway.

[00:08:37]Okay, let's uh let's let's do the alignment thing. What I would start with then is to do a very serious serious to do a more careful alignment on the uh on the IF string here. Okay, that's the plan.

[00:08:56]Okay. So, uh, a lot of, uh, alignment instructions contain a statement as to where to connect an oscilloscope if you want to do a, uh, sweep type alignment using an oscilloscope, which I do. And here it is. It says right here along with this short oscillator section of gain capacitor through 0.1 microfarad capacitor. I seldom do this, but maybe I will this time. For oscillaph alignment, connect oscillograph across R5.

[00:09:27]Adjust for over overlapping double image of maximum amplitude. What are they talking about there?

[00:09:35]Overlapping double image of maximum amplitude.

[00:09:44]So I think what they're saying is uh you know you're you're adjusting four different uh transformers and and each one causes its own peak and so you could have them all aligned and get one big peak or if let's say one of them is not aligned three of them are you you get a funny shaped thing.

[00:10:04]So you can move this false peak adjust for over overlapping double image of maximum amplitude.

[00:10:17]Yeah, you can also align them off. Get them all lined up but not in the right frequency but they're all lined up and you get kind of a maximum happening but it's not the maximum maximum.

[00:10:28]I think that's what they're saying there.

[00:10:31]Okay, I'm going to set stuff up so we can try this sweep alignment of the uh using my oscillraph.

[00:10:39]Yeah.

[00:10:44]So, we're looking at the schematic to show you something that further suggests that that this circuit is added in in later models. And I have an early model.

[00:10:55]And the hint is the numbering of this resistor right here. See, it's R13.

[00:11:00]Right beside it is R1.

[00:11:03]R1. Usually, they number these things in a in a pattern. Usually starting up here and kind of working down this way. So, you'd expect to find the low numbers here, middle numbers in here, and then the high numbers over here. There's different ways of doing this, but that's commonly what's done.

[00:11:20]R13.

[00:11:22]So, there's R12.

[00:11:25]That's the highest R number below 13. Or in other words, R13 is the highest number. If we look at the uh the uh here we see on the list R13 is right at the bottom.

[00:11:41]And that tells me that what they did was they added this in because this should really be R number one or two based on its position, but it turned out being R13 because they added it in after everything else had been said and done.

[00:11:55]probably again after customer complaints or servicemen pointing out that there's something going on with this radio you're selling.

[00:12:03]So, uh, so that just further justifies what I what I did in the radio by putting this in. Um, what it doesn't answer is are there other adjustments that were made in here that I haven't picked up on? Resistors changed or things like that. Maybe maybe something more was done to try to quell the oscillation, the spurious oscillation. I just wanted to show you that uh it's re reassuring to me now. Uh I'm looking for R3 is what I'm really looking for. And R3 R see this why I think R3 should be over in this area somewhere. Here's four.

[00:12:42]This is the resistor I'm supposed to connect my oscilloscope across.

[00:12:52]Where's R3?

[00:12:57]This is a little odd, too, because look at the numbering here based on what I was saying.

[00:13:02]Uh, this number should also be uh a lower number.

[00:13:07]Four. Where's three? It's right in front of me here. And I I'm not seeing it.

[00:13:12]Eight.

[00:13:20]R. Where's R3?

[00:13:23]Oh my gosh, they left it out.

[00:13:27]R2, R1, R2, or R3 should be right in this area here.

[00:13:39]Tell me they removed R3.

[00:13:42]No, I I No, they would remove it from the list.

[00:13:47]Well, for crying out loud, I thought I'd just take a second here and I I would be showing you R3. Maybe it's way down the somewhere stupid. Shouldn't be R3.

[00:14:00]Is it the volume control? No, that's R5.

[00:14:04]Oh my gosh, that looks like 11 7. The numbering is kind of weird here. This This looks This looks It all looks weird. Maybe my theory is baloney.

[00:14:17]Uh, okay. No R3.

[00:14:21]This is weird.

[00:14:24]Um, so, so normally where you're where you're you're attaching it is, um, in this circuit here, you'd be hooking up your oscilloscope to watch the, uh, the rectified output of the of the detector.

[00:14:38]So, you'd be hooking it up to spots like right here.

[00:14:43]There's no R3.

[00:14:49]I'm going to stare at this for like an hour trying to spot where R3 is hidden.

[00:14:55]Maybe maybe you saw it and you're yelling at your screen. It's right there.

[00:15:02]Well, you would think it would be just right in here. Why not? Six, five, four, three.

[00:15:17]There's no three.

[00:15:20]You tricky people. You.

[00:15:27]Okay. Uh well, I just do what I what I would normally do, which is I would connect it uh right here.

[00:15:36]Um.

[00:15:39]Wow.

[00:15:41]Okay, that's enough staring for R3. R3 is not in here. Well, then what was R3 doing that they no longer have it?

[00:15:52]Huh.

[00:15:55]That's kind of weird, too, because they they mention it in the instructions.

[00:15:58]Let's get the instructions up here.

[00:16:01]And on the same page is this diagram. Let's look at this one.

[00:16:08]Is there an R3 in here?

[00:16:11]But uh where where did I get this particular one from? Now one one of you viewers, Jeff, you sent me this marked up one.

[00:16:30]Uh, and you've sent another one. I haven't looked at it yet to be honest with you. Um, maybe I should take a look at the other one.

[00:16:40]Oh, Bert, can you not see the distress I'm experiencing? Bert, he's come in to comfort me.

[00:16:51]Ain't no R3 on here either.

[00:16:55]Wow.

[00:16:57]Four.

[00:17:00]Six. No number here, but that's five.

[00:17:04]>> Okay, bird. Because I I'm getting nowhere here. I'm just I'm circling I'm circling the drain here.

[00:17:15]Okay, let's uh Oh, I just got a phone call. The strangest request I've ever gotten. Can I fix a circuit board from a 1968 Corvette? Huh?

[00:17:27]What? No, I cannot. That's the weirdest request I've ever gotten. I get I got a lot of strange requests here. People with old stuff thinking I can do something for them, but no. Okay, so let's start with the oscilloscope. I have a camera sitting here so we can look closely at the screen when the time comes. Right now, I just want to make sure it's set up correctly. So, I have the this input here, the uh the channel one input. It's actually the output coming from this sweep generator here. This is the sweep output and that's what's driving the uh scope uh this way. It's a special setting here. If if I go to the regular setting, you know, that's a regular thing a scope does. Setting it down here, it then accepts an input from another device because gives it the sweep.

[00:18:16]And I have the sweep range set from, let's double check here, starting at around 420 kHz and continuing up to about 520 kHz.

[00:18:29]Okay. Oh, here comes Bert to help out.

[00:18:33]Something going on in here, he says.

[00:18:36]Okay. Always fascinated by the glass moose. Yes, the glass moose.

[00:18:44]Uh so that should be the oscilloscope set up as far as we can do it right now.

[00:18:49]Let me just check the uh like that and it'll it it'll be I have to recenter it just before we use it.

[00:19:01]What are you doing over there, Bert?

[00:19:06]You can't get the line. The line is inside there. You can't get it.

[00:19:11]I wonder if it looks different to him.

[00:19:16]Okay. Now, next thing is um so so this is where I'm taking the signal for the oscilloscope right off the same place I was taking the AVC voltage.

[00:19:28]Um and this this should be ahead of any uh serious filtering, but it it might well we'll just try it and we'll see what happens. I get a different result when I do this with different radios.

[00:19:41]The sweep generator input is going into the grid cap of the 6A8.

[00:19:47]I kind of want to put it into the 6K7 to start and do the second transformer first.

[00:19:54]Um, but it in the instructions says stick it into the 6 A8. It's probably fine.

[00:20:00]We should get a sweep uh shape. It'll either be up or be down.

[00:20:06]It's hard to say which uh which way it's going to go until I do it.

[00:20:11]Man, what are you looking for? You're really in the hunt mode. You don't usually go up on top of that stuff.

[00:20:16]Bert.

[00:20:18]Bert.

[00:20:19]Always trying to get the microphone.

[00:20:21]That's why. How can I get that microphone?

[00:20:25]Yeah. Okay. Well, you work away on that, B, and I'll work away on this.

[00:20:30]So, um, so I already have the scope going. I already have the sweep generator going. It's really a matter of turning on the radio at this point, I think.

[00:20:38]What am I not thinking of?

[00:20:40]uh tools to make the adjustment and making the adjustments. And uh did you just hear something now? Have you heard a thump? That was Bert. Bert, you know, I I'm really not very comfortable with you being way up there.

[00:20:56]Why don't you come down? Come down.

[00:20:59]If I throw something down the hall, will you come down?

[00:21:03]And the answer is probably, you better believe it.

[00:21:08]Okay, I'm going to throw something down the hall to get you out of here.

[00:21:13]I got it. Look what it is. It's a little It's a mouse. You ready for this?

[00:21:20]You ready?

[00:21:26]Down this way.

[00:21:29]No, not back there. Come on.

[00:21:33]Oh, he's got a special exit.

[00:21:37]What are you doing? Don't get distracted now.

[00:21:44]You can't come out there. You can't come out there, Bert.

[00:21:51]Jeez.

[00:21:52]Come on, man. What are you doing?

[00:21:57]Yes, I know. You're going to just You're just Here he comes. There he is. Special exit.

[00:22:06]Bert, the toyy's down there. Go get it.

[00:22:09]Go get that toy. Get going.

[00:22:12]Don't be distracted. Keep going up. No. Come on. Look.

[00:22:21]Oh my gosh. Cat. There you go. And I'm going to close the door on him. Oh, isn't that terrible? I've closed him out. He's out. Okay, it's just me in here now. That's probably better anyway because this is a little bit fidgety what we're about to do here.

[00:22:41]Okay. Um I think we're all set here.

[00:22:48]Okay. Uh do I have an I think I have the antenna connected, which is not a good idea, but I and I have the short. I didn't really show that, but there is a short installed on the oscill this green clip and that yellow capacitor is a short on the oscillator capacitor to stop the oscillator local oscillator from doing its thing.

[00:23:13]Okay, that's what they recommended. I don't normally do that. Here we go.

[00:23:22]Okay, nothing bad happening.

[00:23:33]Once we get it operating, I'm going to have to leave for a little bit and let it warm up.

[00:23:40]I did not think about how to make the adjustments on this. Okay, let me switch to the other camera here.

[00:23:50]Ah, look at that. Very dead center. It's just a coincidence that it's dead center. Little tiny bump there. Now I'm going to up and down the uh strength of the sweep.

[00:24:05]Yeah.

[00:24:07]Clear.

[00:24:08]That's with the volume at zero.

[00:24:20]That's interesting. So I can that the slow pulsing. I can I can hear that in the sound too exactly that. I don't know what exactly is the frequency right here. I can't be sure. I have to bring in another uh signal generator to to identify that exactly.

[00:24:43]Well, we're getting the result we were after.

[00:24:46]I'm putting in a fairly low level signal here.

[00:24:52]You can go way higher.

[00:24:57]And maybe we should do that. Let me blast it way up here.

[00:25:04]Some pretty weird stuff happening. I'm going to put the uh up here.

[00:25:21]So I think you're seeing a slightly delayed effect of the uh capacitors in the ABC line. So that this thing comes down and then you can see within just a moment it changes its shape slightly.

[00:25:39]You can also see that the shape isn't quite right here. It's uh it's got a lump on the right side. And if I if I advance this quickly, you can really see it.

[00:25:51]No, you can't. No, you can't.

[00:25:54]So, the question is, is this 462.5?

[00:26:00]So, to answer that question, I have to let the radio uh run for a while, bring in another signal, a generator, and I wish I could kill the sound on it, but I can't. So, uh, I'm just going to leave it running here while I'm drink some coffee, and then we will attempt to determine exactly what what frequency this this actually is.

[00:26:21]Okay.

[00:26:25]Okay. Finally got rid of my cat. A paintbrush is what it took. A small paintbrush. You saw that and that was great. So, he was out there playing with the paintbrush. So what we want to do now is uh is determine the frequency uh where this guy is there. Um so I've got this signal generator going.

[00:26:50]The output is right here. It's just kind of interfering with the output of this other signal generator. The two of them combined will cause an interference pattern we can spot. I can vary the frequency of this and we can watch the uh interference pattern. Uh yikes.

[00:27:10]Yikes.

[00:27:12]The output was way high on that. So we can watch the interference pattern and then we can spot, you know, based on the frequency written up here what that peak is actually at. That's the theory. So uh it's a little clunky. I'm going to show you the the uh scope now. So, sorry it's on a bit tipped on a bit of an angle, but it is. Let's get this out of view.

[00:27:36]Okay. So, I'm going to increase the strength of the sweep.

[00:27:42]And now I'm going to bring the uh other signal generator uh around 462. And we'll see what we see on the one you're looking at.

[00:27:52]Okay. 462.

[00:27:56]Went right past it. I didn't see a thing. I'll turn it up.

[00:28:01]Okay, I can see a little bit of action now. Turn it up.

[00:28:09]There it is.

[00:28:12]So that that funny squiggle, I'll move it more slowly. I'm just tuning through.

[00:28:17]There's a point where it becomes quite balanced right there. Let's say looks very balanced and I can read the frequency.

[00:28:25]What's the frequency count?

[00:28:28]462. It's exactly where it should be. So that uh that's good. I did a good job on the first alignment or somebody did a good job on the first alignment.

[00:28:39]Okay. So we've proven the frequency.

[00:28:43]Now we want to uh shape that curve uh because it's just a wee bit fat on on this side here.

[00:28:53]Come back here.

[00:28:57]And uh to do that with a little screwdriver.

[00:29:03]This is a little awkward for me.

[00:29:10]I didn't I didn't think about this part.

[00:29:12]So starting with the second.

[00:29:19]Wow. This is not good.

[00:29:22]Okay. I think I'm in a Oh, I can't I cannot cannot do it like this. This is not going to work out.

[00:29:31]I'm just reaching around trying to do something blind. I have to turn this whole radio. And the thing about is that the speaker do this live.

[00:29:45]So, I'm going to turn the power off here on the counter. Okay.

[00:30:08]Okay, I can see in there now more or less.

[00:30:14]Okay, anything bad happen here? Did we anything short out or move around?

[00:30:23]Everything looks good. Remember I got the local oscillator blocked too.

[00:30:28]Okay, radio back on you go.

[00:30:39]And I'm going to put the uh let me see if I can get that image up onto our screen here.

[00:30:49]I'm so loud.

[00:30:55]It is loud. And we just cut cut the signal back. You know what? I can make this more sensitive and then I'll I'll be happy there. That's probably a better way. Okay, I'm going to get that screen up onto uh provided I know what I'm doing. So, we're going to stick it on the We normally don't do this on camera. We're going to stick it on the left side uh towards the bottom. So, pick number three and we say that right there. There we go.

[00:31:30]And uh that's good enough there. That'll do.

[00:31:37]That'll do the trick. That looks really big on the big screen.

[00:31:41]Very good.

[00:31:44]Okay. Now with the screwdriver changing the shape of that curve.

[00:31:50]Um let me widen it out. So I can widen it out by shrinking the uh sweep range.

[00:31:57]So we're going to we're going to stretch it out this way and then stretch it out this way.

[00:32:06]I'm going to jack it up.

[00:32:16]See? Oh, I just bumped the bump the wire. What happened there? There we go.

[00:32:23]See, there's a a little bit of RF right in here.

[00:32:27]Watch this.

[00:32:30]Really funny shapes in here. You have to really use your imagination, but it's almost like there's something rotating slowly in here. And I see some kind of interference happening right up in here.

[00:32:41]You can't see it because it's just not clear enough on the video. Can I Can I possibly make it clear?

[00:32:50]Well, still having trouble seeing it.

[00:32:54]Okay. Um, overlapping maximums.

[00:33:03]That's what it asked for.

[00:33:21]Did I not do this? Did I Maybe I just checked it and then didn't actually do any uh any changes because this screw is stuck and I don't want to put too much pressure on it.

[00:33:37]bigger screwdriver.

[00:33:39]There we go. It's not stuck. It's just very hard to turn with the uh with with with this slowly pulsing things. Very confusing for me.

[00:33:56]What would that be?

[00:33:58]Two frequencies that are beating against each other somehow. What what two frequencies would beat and produce a uh that looks like a takes about 5 seconds to cycle?

[00:34:13]That's a good question in itself. Okay, other screw here.

[00:34:22]So, I'm using a metal screwdriver. Um, if you're doing capacitors, you can often get away with it, but once in a while, some kind of short circuit can happen up here. be a little bit exciting.

[00:34:33]So, this one you can you can see it's here and I'm going to turn and now it's moved down into here and now it's going out this side.

[00:34:42]You can really see it out there.

[00:34:50]Yeah. Crazy. Yeah. Okay. Now, in the first first one, they aren't really making much difference here at all. Uh because there's nothing particularly wrong here.

[00:35:12]The other thing too is that there there's a certain uh I would want to say linearity, but maybe you should not expect this to be a perfect curve. should be a little bit stretched out on one side.

[00:35:26]And why would I say that?

[00:35:31]Okay, last last one here.

[00:35:44]That looks about as nice as you can get it right there.

[00:35:50]the the width of this determines uh how how much high frequency sound is going to come through, how how much treble is going to be in the uh sound that gets produced and you know really it's the width up in this area here too. So that's usually controlled by the way in which the coils have been wound and the positioning of the coils and stuff like that. There's not a lot you can do about that.

[00:36:16]Okay. Um, let's I got the other signal generator still going. So, let's bring it in and just make sure that's a little too high now.

[00:36:44]So, I'd say that's the middle right there.

[00:36:48]And what do we got? 461.

[00:36:53]So where? So let's me put this to 462.

[00:36:56]Watch the thing.

[00:37:09]I'm probably just not adjusting this way.

[00:37:16]Seems like we're just a touch low. Would it really matter? Um, we're talking 1 kHz. I guess it throws the pointer out by 1 kHz.

[00:37:26]Um, no, it won't really matter.

[00:37:29]Okay, that's good. There's nothing more to be gotten there.

[00:37:36]Uh, why we got all this stuff hooked up?

[00:37:39]And I got the oscillator killed.

[00:37:42]What happens to that uh problem on the short wave band?

[00:37:48]What What band am I doing this on? It shouldn't really matter. Probably have it on the short wave band. It's probably where it is.

[00:37:57]And the answer is no, it was not. Now it is.

[00:38:02]So, we would want to tune it into that zone. And I can't see the pointer.

[00:38:08]Oh, but I can see the scale on the back.

[00:38:11]Sure.

[00:38:26]So, I think I'm I'm actually going the wrong way.

[00:38:28]>> Yeah. I'm I'm I'm far from the zone. So, we're going the other way.

[00:38:40]There's just nothing happening at all.

[00:38:43]Nothing. Okay, we saw nothing.

[00:38:46]Too many signal generators connected.

[00:38:49]Okay, so this has had a very minimal impact on the operation of the radio. We basically made really minimal adjustments here. So, the next thing would be to go through the rest of the alignment process and do it using a try to do it using a sweep.

[00:39:05]And I think I'm going to do that tomorrow. Um, gee, there must be something more I can add. I'm a little concerned that I didn't see the uh the effect here.

[00:39:16]The local oscillator is off.

[00:39:20]We did not see the effect.

[00:39:23]Is that saying the effect is from the local oscillator?

[00:39:26]I don't know. I got so much stuff hooked up here. I gota I'm going to dehook this. I'm gonna put the radio into its normal state here. Except for the local oscillator. I'll keep that shorted out.

[00:39:38]And we'll take off this uh certainly the uh um stuff on the cap. I can do it right now.

[00:39:48]Why? Why not? Make sure the radio's turned down, which it is. Just take this right off.

[00:40:03]We have no antenna. We have no antenna.

[00:40:06]Oh, why do we need an antenna? Because uh because we don't actually need one.

[00:40:11]We're trying to spot this problem.

[00:40:13]Problem on the meter. On the meter.

[00:40:16]On the meter. Put the meter the meter's and scope still connected.

[00:40:25]This should be doing the trick. It should do the trick right here. I'm going to move the camera here.

[00:40:33]Oh, I still got this thing up on the screen. Let me get off of the uh um Okay, let's see the meter down here.

[00:40:49]It's set to can see a small DC voltage there and should be listening to it now.

[00:41:00]Not with that, with this.

[00:41:03]So there's really nothing there if I touch the antenna.

[00:41:07]No, no effect.

[00:41:10]Just because the local oscillators can you just caught what what I just did there. I just touched the grids.

[00:41:38]I touched the antenna.

[00:41:49]Why? Why? Why is that so different?

[00:41:54]It should sound just about the same.

[00:41:59]Don't do it again. You're wasting time.

[00:42:02]H, that's a little odd. Let's try a different band here. Maybe I'm in the dead zone. Don't realize it. Okay. Band B.

[00:42:17]Yeah. Okay. Band A. Volume down here.

[00:42:31]Why why such a difference here? I mean, basically this connection, aside from some coils, is connected to the grid up here. And so, you should hear pretty much the same thing, I would think.

[00:42:47]Very much the same thing. Why Why are you not hearing it on short wave?

[00:42:54]I think I'm encountering another issue here.

[00:43:00]We turn the volume up high enough.

[00:43:05]H we still have this terrible hum.

[00:43:14]What a radio. Okay, I got to stop for today. I think um tomorrow we'll go through the remainder of the alignment situation just to be absolutely sure it's aligned properly, especially the image issue on the high band.

[00:43:30]Uh oh, I have the oscillator blocked.

[00:43:36]Is that why?

[00:43:41]That's an interesting That's interesting. Hold on. Hold on your horses here. Let's go back to broadcast band.

[00:43:48]Okay, this is broadcast.

[00:43:52]There's no local oscillator to convert any frequencies. So, the only thing you can hear coming out of the speaker are signals at the IF frequency.

[00:44:06]Would that be true?

[00:44:13]Well, I I don't know.

[00:44:17]Now there is a uh a IF trap circuit here designed to prevent this kind of stuff. You know I've always been very curious about radios in this respect that if you present them with a frequency at the antenna which matches the IF frequency won't go right through.

[00:44:36]Normally what you've got down there is just some noise. So a little bit of noise comes through. Unless you're unfortunate in your house, there's something issuing a powerful interfering signal right at 455 or 460 or whatever the IF is that could show up in the speaker. It would be the same no matter where you tune the radio.

[00:44:56]Same no matter where you tune the radio.

[00:45:08]So, is that what's happening here? We're hearing what exists at the IF frequency here in my shop with all the noise and all the equipment and all the stuff.

[00:45:18]There's that much noise. Now, there's supposed to be a trap here. I had not done the alignment on the trap.

[00:45:24]Well, why don't we end with that? Let's end with that cuz I have the proper frequency here.

[00:45:30]Uh we should be feeding that into the antenna.

[00:45:35]Yeah. Let's see what happens here. Maybe this trap uh ground the antenna.

[00:45:53]That's interesting.

[00:45:58]So, conceivably this is exactly the right frequency. Now, I don't have a tone on, but I'll put a tone on.

[00:46:04]What? I don't hear the tone.

[00:46:08]Oh, okay.

[00:46:10]Hear it now.

[00:46:13]Oscillator's blocked.

[00:46:20]Good. Have to blast our ear off.

[00:46:25]So, this is this trap not trapping or or not trapping as much as you'd want and adjusting it. Look. Look at how they've got it in the radio here. Got it. is you got to come up with a screwdriver under it. How are you ever going to adjust that?

[00:46:42]What were they thinking when they put that in there?

[00:46:46]Need a little teeny tiny screwdriver.

[00:47:11]Ah, looking for my mirror.

[00:47:15]Not spotting it.

[00:47:17]Okay, we'll use this one here.

[00:47:25]Yeah.

[00:47:36]So, the idea is to adjust this for the least signal coming out.

[00:47:42]I don't know if I can get in there with this.

[00:47:45]So, you're going to get a shock from There's nothing I can get a shock from.

[00:47:52]Oh my gosh, this is just crazy.

[00:47:57]Why Why would they have it like that and not turn the way it should be?

[00:48:02]Like like the way it would be convenient. Is Is it movable? No.

[00:48:09]Soldered right in there.

[00:48:12]Holy smokes. This is a crazy situation.

[00:48:16]Uh be easier if the radar were on a different angle. I'm going to have to go down on my hands and knees here.

[00:48:35]What is going on there?

[00:48:39]Some kind of goop on it.

[00:48:42]Maybe it's been locked.

[00:48:45]Something like a dried wax on it. Am I going to be able to even turn that?

[00:48:58]You can tell I'm down on my knees. I the angle of my arm. This is too big.

[00:49:05]How am I going to do this? I don't I don't see how you can even do this.

[00:49:12]How can you even Come on. This is crazy.

[00:49:20]Well, uh, that is crazy.

[00:49:28]I do have some, uh, angled screwdrivers, but they're great big metal things. I don't like swinging them around near a radio.

[00:49:39]Even shorter, like a a screwed stub.

[00:49:43]What about one of these guys? How about I try more of these?

[00:49:48]Can I possibly get in there? I don't think I get any like hand power on it.

[00:50:09]Battery loose.

[00:50:13]This is crazy. I'm not seeing anything.

[00:50:20]Watch out.

[00:50:23]This is not going to work. What am I going to I can't I can't turn it anyway.

[00:50:26]I got no turning power.

[00:50:31]So, the uh the threads screw is sticking out the back here. They grab it with pliers and do something really crude.

[00:50:50]I don't know I'm doing anything here cuz I'm ruining the threads. So, we do have the meter here we can keep an eye on.

[00:51:03]would be loosening this way.

[00:51:10]H why? Why the jumpy behavior?

[00:51:30]Am I turning anything? Is anything happening here?

[00:51:49]Guess we'll be tightening it.

[00:51:54]This isn't Great big screwdriver.

[00:52:09]I'm really not sure I'm doing anything here.

[00:52:19]No, let's use this shorter thing.

[00:52:23]I got longer ones of these.

[00:52:26]Let's stick a nice electrode in the radio here with my hands on it.

[00:52:39]Wow.

[00:52:45]Oh, I've definitely turned it. You know what? I can watch it turn from here.

[00:52:50]Oh, yeah. It's turning. Okay. So, I am So, is it still turning? It is no longer turning.

[00:53:12]Make any sense of this?

[00:53:24]something something quite weird about it. It's not behaving the way I would expect at all.

[00:53:34]Um, this this coil is, let's just peek at the schematic here. The coil I think is designed just just to feed the signal to ground here. Um, yeah, it's just ground here. So, how about I just ground it right across it and see what happens, which is probably easier said than done. No, probably easy easy to do. Uh uh uh something different.

[00:54:10]Um the they they're in series, aren't they?

[00:54:18]Yeah. So these things are in series. So I have to short all the way across the two of them. I can see the interconnection here. So it'll be across those there. What do I think's going to happen?

[00:54:29]Well, if it's if it's blocking the signal at all, then this will unblock it and we'll hear it increase.

[00:54:39]I think that's just ground there.

[00:54:45]Nothing whatsoever. No, no effect.

[00:54:53]No effect.

[00:54:58]This is It's definitely in the circuit.

[00:55:18]No, let's keep doing this.

[00:55:23]So, we're going to we're going to loosen them.

[00:55:29]I'm watching the meter maybe. Oh, yeah.

[00:55:30]You can see it, too.

[00:55:33]It's Oh, it's loose. It's very loose.

[00:55:37]Okay. So, loosening it more is not going to make any difference. I don't think so. We're going to tighten it. Now, which way is tightening?

[00:55:46]This way.

[00:55:48]Watching the meter. Just there it is right there. That's it. That's as much as we can do.

[00:56:10]So, we take this off the antenna now.

[00:56:22]only so much you could do. Okay.

[00:56:25]I don't know.

[00:56:29]Ah, old radios, you know. Well, I'm going to stop at this point. Um, so there's no question the if is tuned properly. What happened on the shortwave band in the end? I don't know. I don't know. I don't know. Why can I not figure that out?

[00:56:47]Because I still have the uh short on.

[00:56:50]So, let's go watch this. We'll go through the thing and then I'll take the short off the local oscillator. We'll go through the thing and see if this affect the when I say go through the thing, I mean we'll tune through the band. Okay, we're deep in the bad zone. Let's get out of the bad zone.

[00:57:08]Oh my No local oscillator.

[00:57:25]How is it you can get this kind of effect?

[00:57:35]Way up. Way up. Way up. Okay. Now we're going to engage the the local oscillator.

[00:57:48]Okay, that should be back.

[00:57:54]Hear any difference at all?

[00:57:57]We're we're out of the dead zone.

[00:58:02]Yeah, there's no there's no antenna connected. So that's why we're that's why the radio's so quiet. So, we'll just watch for the dead zone to show up. We don't need to hear a signal.

[00:58:15]Can hear the radio.

[00:58:17]Oo, there's that. There's that spot.

[00:58:23]Oh, wow. Just that spot. You get a full oscillation there.

[00:58:42]antenna. Let's put the antenna on. I think it's just so I have some reassurance that the radio is in fact operating, which I'm pretty sure it is.

[00:59:24]Right. That's the dead zone.

[00:59:34]Another spot.

[00:59:36]See the ABC voltage.

[00:59:42]Weird stuff going on with this radio.

[00:59:44]Like really strange stuff. There's another one.

[00:59:51]Okay. And broadcast band cuz that's what's really important.

[00:59:59]Look at the difference. Wow.

[01:00:11]So, a couple things here I've discovered today that's come quite clear. Uh, one is the lack of sensitivity on both short wave bands. It's very, very poor. I discovered that by the fact you can touch the antenna with my finger. I can touch the antenna with my finger and no no response compared to the broadcast band.

[01:00:30]So, what's the difference here? Because there isn't a lot of differences in these in the way the circuit is designed. Why why would the short both shortwave bands be down so much from the other?

[01:00:44]Okay, that's a question I'm going to ask tomorrow.

[01:00:47]So, uh um I have a lot of fun doing this, by the way. I don't mind being stuck and hunting around. I find that that's fascinating and lots of fun to do. uh may not be quite as much fun to watch because you may be, you know, you want a result while you're watching, but uh no result. No, no particular result.

[01:01:12]Okay, that was fun.

[01:01:15]Uh we'll see you on the next video.