Good job showing off that Magnavox. Solid State and a modern assembly. In 1965 some companies were still selling tube sets and hybrids. A side note, The FCC had just ended AM/FM simulcasting. New programming brought listeners to the FM Band. AFC compensated for drift in the values of the electronic components. The need was eliminated later on by frequency synthesizer circuits.
Even a lot of vintage solid-state radios also had the switch settings for either FM or FM AFC. Yes, in modern radios; especially those using digital signal processing (DSP), the need for AFC is often eliminated because the DSP can handle signal strength variations more effectively, I think perhaps the AGC was even eliminated. I think were on the same page here. Thanks for watching and the comment.
I am SUCH A FAN for ALL these old tube type radios. They REALLY exhibit such warm sound that NO solid state radio can. They were the Real McCoy of the early eras. Built out of wood 🪵, or steel. Bakelite is another GREAT 👍 technology material for radios 📻. I never have gotten over the glow of the dial lights on these radios. The ones with bigger speakers 🔊 had DEEP BASS!! Your friend, Jeff!!
Tubes just love to cause us trouble lol. Also, I've never seen a power cord coupling to the circuit like that before Ken. Well done again on a great looking radio
It seems like the radio is drawing very excessive current if the B+ voltage is dropping and the rectifier is getting hot. Also, if the sound is clear at first and becomes garbled after the radio has been on for a while, most likely, the audio output tube has grid emission, and the grid voltage drifts positive as the tube warms more. Try a new tube. Also, check the grid resistor for proper value and the coupling capacitor from the plate of the first audio tube for leakage. This is a common problem with paper capacitors.
Thanks, Michael, for your informative comment, always great to get them from my viewers. I replaced all film capacitors and resistors that were out of tolerance, shown in this part 1 video. The selenium rectifier being old had very high resistance and was causing the 45% drop in the B+ voltage. Were on the same page here and by replacing the 19V8 first audio tube, that corrected the distorted sound issue after the radio got to operating temperatures. So, the plate from the first audio tube was causing the voltage variation to the control grid of the output tube. Can’t depend on tube testers at times where they respond differently under a real load. All the best.
@@kenslab1973 Selenium rectifiers do degrade with age, and they should be replaced with silicon types. You may need to add 47 to 100 ohms in series with the silicon diode to match the normal series resistance of the selenium rectifier and keep the B+ voltage from getting too high. Use a flameproof or fusible resistor, because if the silicon diode, or anything else in the circuit, shorts, this resistor will be the fuse to protect from further damage or even fire. The first audio tube itself will not cause the output tube to draw too much current; how much current this tube draws is determined by the voltage on its control grid relative to its cathode. With most radio output tubes (such as 35B5, 35C5, 50B5, 50C5, 35L6GT, 50L6GT), the cathode bias resistor is usually 150 ohms and drops about 7.5 volts, making that cathode 7.5 V positive relative to 0V circuit common. The control grid is biased at 0 volts by a large value grid resistor, usually 470K ohms, also connected to 0v common. If the output tube grid is more than one half volt positive, the coupling capacitor from the plate of the first audio tube is leaky, the grid resistor is open or very high in value, or, especially if the current climbs and the sound degrades with time after the radio has been on for a while, the grid of the output tube is contaminated with some of the cathode emissive coating material and is trying to become like the cathode. As this happens, the output tube plate may start to glow red. Obviously, the tube is bad and must be immediately replaced.
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hehe cool, for a second i thought that was a working radio circuit, and the sound came out of the speaker eyes. That would have been something else. Maybe in the future even AI powered so they can move around and talk. How could you be sacred of AI robots if they looked like that? They could teach us electronics.
I don’t exactly know what you’re referring to; if it’s the 3D woman character, I always like to add something different in my videos from time to time. Thanks for your comment.
Thanks for the request; I plan on doing some more TVs in the future but their hard to come by, especially when I prefer them to be color TV’s and in non-working condition.
One of the few mistakes not caught by Philco and republished in Rider's. Look at the two E cap connections on the parts location diagram for under the chassis called Figure 5. It is where C28A and C28B have nothing connected to them! C28B should have a connection to pin 6 of the 35C5 and a wire from C28A should go to ground. The wiring diagram itself is correct. Just like to vet information thrown at restorers just to see if we can realize that people made mistakes, even back then. Can't recall how many times I found diode symbols in reverse in circuit diagrams by Howard Sams over the years.
Thanks Steve, I did use the Rider’s schematic and all E-Caps connections were spot on as you mentioned. The green negative wire was wired to all E-Caps internally when I re-stuffed it. I agree about the mistakes made on circuit diagrams, I have found mistakes on Rider’s and even the actual PhotoFact’s over the years to include alignment instruction. It’s always nice to get heads up on possible issues. God only knows how many mistakes I made myself.
Very nicely done Ken. A hell of a lot of work but well worth it. I thought the MP3 mod was also a nice touch. A great looking radio, you're to be congratulated :)
Jose, I purchased my radio stand about 12 years ago and have no idea how much it cost me back then. I got the small one, here’s the web address. www.radiostands.com
They made plastic radios in the 1940's and '50s? I presumed their cabinets back then were mostly bakelite, wood or metal. Nice repair there. You tidied the radio up and made it happy again. 😎
Good question Frank, I'm not really sure about the exact function, I think I mentioned that perhaps it could be for EMI noise, but it also could be to filter out high frequency noise just like a previous video I did where the positive end of a 2uF electrolytic capacitor goes to ground.
Thanks, I really like the clicker type remotes, pretty expensive even back in those days; I’m guessing, with the receiver, motor, gears, gear case, and relays.
woo hoo one that works. Great job solving all those problems Ken and a really nice finish having you on the screen wrapping it up. You're a marvel with these things.
Philips black and white tv’s in the late 60s did this very thing it was the lopt (or flyback) every time. If you can check your EHT it might be low. Replace the lopt and the black circle will be gone.
I really didn’t check the flyback final anode voltage since I did have a raster. If that’s the case it would be near impossible to find a flyback or even an equivalent one to replace it with. Anytime there’s a defective flyback or a deflection yoke where it’s not a simple fix, the TV is un-repairable to me. Thanks for your input.
Is it the korrekt transformer ? Somebody may have had to change it and didn't get the korrekt model. I don't really buy the idea that the phosphor has gone bad... The whole surface ? But one way to find out is to hold an old clock with phosphor in front of the tube and see if it lights up.
Perhaps, but I think the vertical, horizontal power transformer/flyback and the deflection yoke are all original, although the flyback and yoke passed the ringer tests I’m thinking that there still could be the possibility that one of them respond differently under load and even after a spot on voltage tests prior to installing the chassis back in the cabinet. I need to purchase a ringer that will test said items in circuit under load. I’ve never seen a picture tube go completely dead as far as degraded/deteriorated phosphor. Years ago I’ve only read about such things and I think it’s possible. I’ll try you idea with the phosphorus clock or watch for that matter. The TV is still on the back burner in the event I do acquire a dedicated in circuit ringer tester. I disagree about this TV being low hour set though. Thanks for watching and your input.
We all make rookie mistakes Ken lol, but they're good to show the beginners. I checked out Nostalgia and was able to download a schematic, not sure why you cant? BTW, you are finding some great looking radios
Yeah Frank, I show my mistakes to also show that I’m only human; viewers hopefully learn from them. I still can’t download on Nostalgia; I don’t know if it’s here in the States or my antivirus protection changed, I’m thinking the latter.
@@kenslab1973 Ken, I just used my VPN to connect to the net via the USA and was able to download a schematic. Try turning off your anti virus and see if that resolves the issue
Beautiful set, this one is in great condition for sure, and the tube looks in good shape just judging it by how bright it can get, too bad the camera didn't do it any favors. I have this exact model, one of the few mementos left from my dad before his passing, sadly mine is pretty dim and washed out, we used it a lot so the tube is just tired. Still very worth keeping around as aesthetically is very pleasing and since it's small it doesn't take too much space.
Thanks Frank, I didn’t check the pin-out on these checker pieces but obviously all three had the same filament pins. I thought I was going to get a copyright strike for the commercial; I had to steal this great idea from you.
@@kenslab1973 Not a problem Ken, the more entertainment we can provide the better. I don't think YT cares about old ads, just copyrighted music. Keep up the good work :)
Bummer Ken. I wish I could offer some thoughts on how to progress but I know nothing about TV circuits. I'm sure something will pop into your head though. Good idea to start on something else
Various manufacturers, I get my capacitors and resistors from just radios in Canada. Everything is coming from Asia, perhaps mostly China today. They specialize in capacitors and resistors for vintage tube radios and electronics. I’ve purchased from just radios for many years and yet had a bad one or one to go bad. Not sure about how old their capacitors are but shelf-time is not a big problem for caps as it was in the past, and the construction is certainly way better than anything that was used when your radio was made. I have capacitors that are 20 years plus old and their all fine today. We all like to get electrolytic caps with the most hour rating but even low 5000-hour caps (not saying mine are) will last 1250 days if you played your radio 4 hours a day and I think they will even exceed that 5000-hour rating. Enjoy your restoration!
I was curious of the values. Curious, if I have a used radio - would you just focus on replacing the caps, or would you replace the tubes as well? Unsure if it is worth all the expense. The AM portion has lost its sensitivity and requires more than normal volume to be turned up. FM works great.
No, never replace all the valves but you do need to have a way to check the valves since they can be bad as far as a weak tube, a grid leakage etc. For example, your AM issue could have a bad 12BE6 AM converter tube, check the 19T8 AM discriminator also. The tuning capacitor for the AM band will cause low reception if it’s dirty, clean it with contact cleaner, fully opened then while closing it keep spraying it with the cleaner. The FM has a permeability tuner so leave that one alone. The AM might need a full alignment to include the IF transformers A1 through A4 then the antenna and oscillator adjustments on the AM tuning capacitor to include the 600kH coil adjustment on top of the chassis. You should have the alignment instructions to do this alignment correctly. If you haven’t recapped this radio you need to do that first before you proceed with the above instructions. Change the electrolytic caps and all the wax capacitors, leave the mica’s along, also any resistors that are out of tolerance. @@thetube577
Lubricate the RF gain potentiometer with contact cleaner spray. The band switch contacts might be dirty or corroded. This can affect AM reception. Try cleaning the band switch contacts using contact cleaner spray. Capacitors and Transistors in Zenith radios from that era generally have good capacitors. However, if the radio was stored in a damp environment, the capacitors could become leaky, affecting volume. Try removing and reinserting the socket transistors, clean the pins and use the red deoxIT on the sockets. Might be the oscillator transistor. One easy way to check that your LO is working is to place another radio next to your TO, with the dial at a blank spot near the top of the dial. Then put the TO on the AM/BC band and tune around between 1100 and 1200 KHz. If you hear the noise level drop significantly on the other radio, your LO is working. If you’re hear nothing on the AM band except when the BFO (Beat Frequency Oscillator) is on, it suggests that the IF (Intermediate Frequency) string is working. However, either the RF amplifier or, more likely, the LO (Local Oscillator) is not functioning. The oscillator transistor could also be defective. The FM RF and oscillator transistors are the same, number 121-687, I think. Swap them and the AM should work, and FM will not work. The oscillator transistor might be bad. Good luck!
