Why Amateurs Should Not Service Expensive Antique Radios: 1930's Zenith Radio

Why Amateurs Should Not Service Expensive Antique Radios: 1930's Zenith Radio - 7S261

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Күн бұрын

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@ON5ALE-Alessio Ай бұрын

At 19:00 the ripple smoothing coil functions as a DC fed electromagnet. Very clever to save copper but.... doesn't that creates a 120 hz hum in the speaker. It is like you mix the Hum with the audio. 2nd doesn't the audio on the other hand get fed back to the DC supply and into all further electronics again creating that sort of echo?

@ElectroRestore Ай бұрын

Your thinking low voltage / high current: solid state. Tube devices are high voltage / low current. That is a major mind jump! So as a tube device, what we have is this circuit in question (C17 Field Coil C19), which is a pi filter, designed to remove the low millivolt 60/120Hz AC ripple off the high DC (B+) line. Keep in mind that the B+ is up around 300-375V DC! The percentage AC voltage ripple, before the the pi filter, is 5V DC (the filament/heater voltage of the rectifier tube). That is 5vac/300+vdc = 1.67% pre-pi filter. Another way to look at it is: a B+ voltage of 300V DC would be a pulsation DC voltage of 300V +/- 7.07V = 292.93VDC to 307.07VDC. The +/- 7.07V is the peek to peek voltage of 5VDC (5 * 2.828 = 14.14v p-p = sign wave of 7.07p+ to 7.07p-). That is quite insignificant at 300VDC right? And that is BEFORE the pi filter. After the filter, the AC ripple voltage would be a much lower percentage. Perhaps as low as 0.001%. Which at 300V AC is definitely insignificant! Next we have C7 going to ground which the AV ripple would see as a "water slide to ground", while the DC would see an insurmountable wall of concrete! Lastly, the Output Transformer is driven by the amplified audio signal, superimposed on that 300V DC. As for the reflected audio back to the high voltage power supply, who cares? It would be swallowed up and grounded, through the center tap of high voltage winding of the transformer. Again, all these things would be serious issues in a low voltage, solid sate device. And much worst in an analog to digital IC circuit.

@ON5ALE-Alessio Ай бұрын

@@ElectroRestore so that Hum will be bearly or not hearable and the feed back audio wouldn't be of any significance to cause echo or refraction effect.

@ElectroRestore Ай бұрын

@@ON5ALE-Alessio Exactly! Each stage is pretty much isolated from the previous stage by the one-way signal path. On the RF side, you have high frequency filtering through the IF cans (455KHz for AM and 10.7MHz for FM). So feedback there not likely. If you have wires that are not dressed properly in their layout in the chassis. In such a case, it might be possible to get feedback in the oscillator circuit, which has high sensitivity. However, most of it would be stepped on pretty good by the incoming radio station and IF filtering. You would be more likely to get 60/120 Hz hum interference from the AC tube heater wires, if they ran over sensitive areas, than reflected audio signals. Very good questions! Thanks for asking them!

@ON5ALE-Alessio 26 күн бұрын

@@ElectroRestore did they had FM and 10.7 MHZ in the 30's? I mean most radios backthen were single conversion on 455 khz I think. I could be wrong.

@ElectroRestore 26 күн бұрын

@@ON5ALE-Alessio @Alessio-v3o No, No FM until much later. I was just including the different frequencies of IF cans in general.

@davem147 2 жыл бұрын

I have to rate you an "A" for your expertise, but a "Z" for your dizzying video!

@timlincoln2246 Жыл бұрын

I almost threw up. Twice. Tripods are a great invention for some. Case in point.

@praha007 3 ай бұрын

I'm an amateur and I have restored several radio's, tuners, tapedeck and a grundig 2355 tube radio, just for fun and hobby. So it is possible. The person you are talking about in the video was not an amateur, but an overestimating novice with no feeling for components and how to solder them correctly.

@vtjmproductionsusa2390 2 ай бұрын

LoL I have had to do a few reworks that the capacitor queens got lose on. So many think " recapping" fixes everything . Then when it does not work they always seem to find there way to my bench. Great video. 👍

@knifeswitch5973 Жыл бұрын

Tripods are your friend

@ElectroRestore Жыл бұрын

Not really. You can't always get in tight spaces with them. Besides, my channel is free education. I can't afford expensive cameras and tripods and high tech editing software. Sorry! But I can provide valuable techniques and theory at no cost to the viewer. ;)

@fallenfirebird240 Жыл бұрын

As an amature who is actively reading up on electronics and referencing youtube videos, I don't understand how this could get so bad. I typically take it one component at a time and take tons of reference pictures before I do anything. It almost looks like they took a ton of components out at once and weren't sure where to start. Great video as always!

@rpcomms1 10 ай бұрын

Its called inexperience,and a little knowlege is a dangerous thing! Trust me Ive seen some right hotch potched two way radios RF repairs over the years make you shudder..lol So seeing this video as a engineer does not surprise me. Little common sense goes a long way too as shown with cutting and leaving danglers in mid air ether! Learn from other proffesionals is the best way,Yes take lots of photos which is so easier to do now,well done. Why Engineers used to get paid well for there skills and knowledge,sadly the repairs engineers are becoming a rare breed now and poorly paid for their skills in throw away electronics. Good luck learning more usual skills in your quest. Rob P 👍

@sypodj 2 жыл бұрын

Superb explanation thank you 👍 the way you bring it its very easy to understand 👍

@ElectroRestore 2 жыл бұрын

Thank you sir!

@chrisjarvis4449 Жыл бұрын

filmed in shaky vision

@mastdog 3 ай бұрын

I felt like the producer of the Blair With Project filmed this. I could not focus on what they were saying or point out because I got sea sick.

@jeanlawson9133 Жыл бұрын

How is it to become a professional if one is never an amateur...... AIN'T IT JUST AIN'T IT 😜 lols

@ElectroRestore Жыл бұрын

Ha! You got me! lol

@mikepasko7493 2 жыл бұрын

I agree with you 100% I've been saying this for a long time.... that most of these so-called radio repairman on you tube or restores are complete butchers .... especially when they say oh it doesn't have to be exactly that value .... they're saying that they know more then the engineers/technicians back when the equipment was designed... I myself worked for Westinghouse in the 60s as a color TV analyzer fixing the sets that didn't pass the testing ..but a lot of these idiots on KZbin just like to see themselves and hear themselves I believe and teaching the public everything that's incorrect ....I seen them Butcher up and destroy a lot of gorgeous radios and I tell them so also

@ElectroRestore 2 жыл бұрын

Agreed Mike, it is important to me to stay as close as possible to the original schematic, using the parts that are available today.

@andygozzo72 2 жыл бұрын

actually in some cases resistance/capacitance values arent critical, valves/tubes are very 'unfussy', and vary in characteristic a fairly wide range themselves, anyway...

@jamesmann1243 Жыл бұрын

There isn't anything I despise more, than an egotistical uninformed Hack, who would argue with Karl Emde,( lead engineer for Zenith,) that they( the hack) knows more than any of the engineering departments of the major radio manufacturing companies that built excellent, reliable, and SAFE!! equipment that served the population for decades. Now, if its a matter of ignorance, inability to read a schematic, or just hyped up stupidity, hundreds, if not thousands of vintage radios and televisions have been permanently trashed to the point of a parts set, simply because one had no clue and business attempting to repair a unit they were in over their head in. I have seen it way too many times, and yes, the final outcome is usually cost prohibitive to the owner of a family heirloom.

@jimmclay2353 Жыл бұрын

You really need to put your camera on a stand

@towerman75 Жыл бұрын

Zenith has always had a bad rep for circuit design, wiring, and poor documentation. When I worked as a bench tech in a well known repair shop, we had rules that we followed. If you messed up on something, your punishment was to work on all Zenith products that were already in the shop, or the ones that came in for one week. I always got stuck with their stereo's (which I hated).

@clifperry4677 Жыл бұрын

OMG, figure out how to keep the camera more steady, I m getting sea sick.

@jeanlawson9133 Жыл бұрын

This is good stuff 😎 Thanks.....

@Rebel9668 6 ай бұрын

Well, the only way you'll learn is to do it yourself. As you get better at it you can go back to earlier work and re-do it if it needs to be re-done. That is, assuming you own the radio and are doing it for yourself. There are still lots of things I'm unsure of, but that doesn't stop me from trying and learning. I've never had a set I've given more than $100.00 for and most were picked up for far less. The most expensive one I've had so far is a Transoceanic that I ended up giving to my uncle as a Christmas present. When you've grown up and live out in the sticks like I do there isn't much opportunity to work with a repair technician. My Pappy did work on electronics when I was a child, but I had absolutely no interest at all in the hobby back then...especially after he picked up a truckload of tubes and we had to spend days and days sorting them all back in about 1982. By 1989 all those tubes went to a landfill as with no internet or anything else at the time there was no way to gauge that they'd ever be worth anything in the future. Of course, hindsight is 20/20 and when I did finally gain an interest it was far too late for any equipment that my Pappy had once had so I basically started from scratch.

@ElectroRestore 6 ай бұрын

I really enjoyed hearing of your upbringing with electronics,. It brought back memories of my childhood being taught by my dad, who had a TV radio repair shop. I wish intensely, that more young folks were interested in learning to repair these devices! It is sad that not many have your zeal for learning it! The issues is not that they shouldn't do it till they learn how. It is the dangers of learning on a transformer set that sources out upwards of 600-700 volts AC ,and 200-300 volts DC to the plates of the tubes! One wrong touch, in the wrong way, and it's an all expense paid trip to harp land! Also, these devices are getting rarer to find that are not botch by bad service work. What I suggested was that folks learn on All American Five (AA5 and AA6) radios, which do not have high voltages, are cheaper and more plentiful, and easier to rework back to specs if a restore is badly done. You can stirp them to the chassis if needed, and try again, and learn much doing so! Safety first, skills second, expensive and rare device should be last. You have to learn to crawl, before you learn to walk, right?

@Anthonytheredneck Ай бұрын

@@ElectroRestoreI'm 25 now I've gotten a few sets going so far noticed I said going my first was a AC/DC 5 tube zenith my brother got for it was already " cheaply repaired" from the eBay seller a cheap Taiwan no name filter cap. With the ground end crimped to the aluminum can of the filter cap, upon receiving the radio and opening it uo the ground had broken rigth at the crimp, the one mica that would of be in circut of the oscillator to the mixer was changed or replaced with a capacitor tolerance 20% not the 5 % that it should be. The radio has been used for some parts as it was in great shape externally. Wound up building a two tube regenerative receiver based off mike1 I think that's the correct portion of his user name on KZbin I'll edit it correctly. Any how his design was intened for lower b+ im essentially using his circut to but at a higher b+ the oscillator coil has had some turns removed, now I think I'm gonna redone the resistors. Really fell in love with this radios since then. Got me a vtvm,an eico which was in pretty good shape extrenaly electrically the whole voltage divider was 10% or more out of tolerance so got. Got really good 1% resistors from mouser

@ElectroRestore Ай бұрын

@@Anthonytheredneck It sounds like you have quite an aptitude for vintage electronics! Thanks for the comment! It blesses my heart to hear that younger adults are still showing an interest in tube radios and the like! I have tried to find an apprentice around my area, with a basic skill aptitude but with little luck. It may just be my area idk. If you start a KZbin channel, be sure to comment and let me know and I will subscribe. :)

@Anthonytheredneck Ай бұрын

@@ElectroRestore I've thought about restarting, lost my old account a whlie ago do to the sercuity set up. But I think it would be wise as my work ethic is handled a bit more seriously, I work on soild state too, actually were I statred doing first. Being already mechanically inclined at the time and you tube pretty much just came to be about 3 years after KZbin started. 30 watt iron and scarping old boards for their parts like transistors and the wire and so on. Gosh i let the smoke fly doing stuff like that. Much older and it didn't really take long to comprehend how circurts kinda work.

@briankays2635 2 жыл бұрын

ER - THANK YOU! I'm currently working on recapping a Philco 37-61 that has exactly the same issues around the candohm resistor. The schematic is opposite the physical layout and someone got it wrong and it's not connected according to the schematic. I'm a novice for sure but I'm trying to learn and get it right. I spend multiple hours staring at the chassis and reading for every 1/2 hour of actual soldering and replacement. This video (especially the explanation re: smoothing capacitors at ~10:14) was just what I needed to see exactly when I needed to see it. Thank you for taking the time to propagate the knowledge and helping us all figure it out. Greatly appreciated!

@robertedwards3147 Жыл бұрын

I am a newbe and found that my radio to be a mess compared with this one so have removed all and starting from the schematic so far so good using tag strips so no hanging/lose parts thinking that this will be a good sounding radio and easy to service for th next guy.

@hotpuppy1 Жыл бұрын

Correct schematic is vital because you never know if it was messed with before. If it hasn't been touched, best to go one part at a time.

@butterbean4195 10 ай бұрын

hey paul good video. ill be in touch to come get my radio stuff.. stay safe

@Dennis-mq6or 23 сағат бұрын

I see this happen all the time with old tube type receivers and CB sets. A radio operator's license is for operating radios, not repairing them! Find a HAM operator who is NOT an 'appliance' operator, (someone who purchased all his equipment ready to use right out of the box), instead try to find an older more experienced person who can repair his own equipment, especially if he can repair tube equipment.

@basspig 5 ай бұрын

It's a lot of extra work when the customer has installed Parts incorrectly or to the wrong connections because you have to trace point to point everything on the schematic to what's on the actual physical radio. It's a much more involved repair than just repairing something that failed what but was not touched by the customer.

@hav0k337 3 ай бұрын

Thank you for this video. I've learned quite a few things. I wonder, if one wishes to restore such radio to working condition, and finding one of these old speakers is impossible (let alone rewinding the field coil), would it be possible to instead use a modern speaker with a permanent magnet, and any kind of inductive 1250 ohm load on the ripple smoothing side?

@ElectroRestore 3 ай бұрын

As long as the inductor can take the high voltage, yes! But I do have a video showing how I rewind a field coil. It really is not that hard. Actually, you can repair them if they are not too bad by replacing bad spots. If just the speaker is bad, you can put the field coil in the cabinet (if the original one is good). Assuming there is room of course. Then install a permanent magnet speaker.

@charlesharkin2165 Жыл бұрын

This is hard to watch pity

@meesterprofe007 11 ай бұрын

Camera work needs refining

@johnbravo7542 4 ай бұрын

It makes it difficult when the camera is all over the place.

@ON5ALE-Alessio Ай бұрын

Bummer with that field coil. You can t just swap speakers. But if you use a stand aline coil for the DC supply and a 4 ohm modern speaker ?

@ElectroRestore Ай бұрын

You can replace the field coil with a power resistor and that would free up the power supply from the output stage. Than, replace the output transformer for one that has a primary that will work for the load resistance of the output tube (for this 6F6 tube it would be 7k ohms O.T. primary impedance), and a secondary that will work for a 4, 8 or16 ohm speaker of your choice. ;) Note: You can find the load resistance for any output tube in a tube specs sheet. It's easy to get them online.

@johnhood3172 Жыл бұрын

Antique means 100 years old or older.

@miroslavbelik3133 28 күн бұрын

Great information, but iam getting sea sick from the camera jotting around

@a587g 2 жыл бұрын

Zenith was known for tying components together in mid air in their late 30's sets. Saved them a few pennies for a terminal strip. Not those filter caps though, someone should've used a terminal strip! I've seen a number of bad field coils in 1936-38 Zeniths. Usually what happens is the second filter cap shorts, and causes too much current to flow through the coil, burning it out. But it seems Zeniths are especially prone to this problem. It's possible the coil was already open before the previous repairman worked on it. They clearly didn't use the schematic, so I wouldn't put them past not testing the field coil before they started! I've also seen bad oscillator coils in these 1938 models, and of course the candohm is always unreliable.

@ElectroRestore 2 жыл бұрын

I agree that a person that would do such sloppy work would not think to test the FC for continuity before recapping. However, the filter cap was definitely in the wrong place, which indeed passed excessive current through the coil. The candohm resistor, amazingly, had no bad sections and was in acceptable tolerance for a voltage divider to handle the B+ current through the FC; had it been in series and dropping the voltage as required.

@murruti1967 Жыл бұрын

gracias por compartir tu expriencia. No sirve a las nuevas generaciones aprender de ellas.

@MrGigi-dz9cv Жыл бұрын

Condensers, don't 'convert' AC to DC. Rectifiers do.

@ElectroRestore Жыл бұрын

Rectifiers indeed do convert AC to DC by allowing current to flow in only one way. However, the DC they produce is fluctuating DC, also known as pulsating DC. It is not pure DC! It has an AC component to it. The only way to remove that AC (in a tube type circuit), is with a capacitor(s). Capacitors store charge like a battery, which is pure DC. Put an pulsating DC charge on it, and it dampens it via it's regulation properties. The only way to alter the DC voltage on a capacitor is by putting applying a greater DC charge, or a charge in the opposite direction. Therefore, they are the necessary components in true AC to DC rectification.

@MrGigi-dz9cv Жыл бұрын

@@ElectroRestore Maybe Pulsating current îs better.

@ElectroRestore Жыл бұрын

@@MrGigi-dz9cv No, Capacitors store voltage, not current. They store Electromotive Force (EMF) in the form of a charge (like a battery). The E is why Ohms law is not V=IR. But rather E=IR (or I=E/R or R=E/I).

@billysharp3388 Жыл бұрын

Well are you going to do it right by checking each capacitor on a xy scope and make sure you put each capacitor in the right way? I am not talking about filter caps either they are marked others aren’t and if you don’t put them in right they will cause noise. Not a good idea to talk down hams!👎.

@ElectroRestore Жыл бұрын

Always do! :)

@Dogface1984 4 ай бұрын

Any recommended inexpensive sets to practice on ??

@badraven_indieauthor Жыл бұрын

I agree, and YES we all have to start somewhere. I collect old radios, but restore cheap old radios. It is good to learn, but some things should be left to the experts. Especially, an expensive piece of history!

@hestheMaster 2 жыл бұрын

Unfortunately novice radio repairmen never consult a proper schematic, nor do they take notes, nor do they understand what they are looking at compared to the schematic. They also have components sometimes just hanging in the breeze. When going over a previously touched radio you have to check everything the last person did AND the existing wiring and components. Basically double the work for a restoration .😒

@ElectroRestore 2 жыл бұрын

Exactly! Twice the work and diagnosis time! The good side, if there is one, I guess would be the radio should end up even better after the detailed analysis and painstaking repairs.

@andygozzo72 2 жыл бұрын

you cant always blindly trust even official schematics, there may have been changes during the production of the set which wouldnt be in an original issue service sheet, or vice versa, you may have an early set, but schematic for a later one, and this isnt always stated... even more variations likely in any set produced during wartime due to component availability problems....it may also have been modified for various reasons, maybe due to not being able to get correct parts, so altered to suit others

@vancouverman4313 9 ай бұрын

Unfortunately, Mr. Carlson and yourself dont take on many apprentices, so people are forced to learn by trial and error.

@ElectroRestore 9 ай бұрын

Trust me, I sure have tried to find some young folks that would want to learn in my area. If we cannot pass this knowledge on, it is just a matter of time that these radios will be tossed to the landfills because no one will be able to service them. I mean us old timers are dying off. I am kind of a youngster in the field at age 64. I don't get to make as many videos as I'd like. Due to the declining number of techs, my work load is quite extended. I am not a hobbyist but actually run a restore business. Maybe by time I retire, I'll find someone that has an aptitude and desire to learn vintage electronics. :)