13:54 Holy crap! What a precise job of soldering those surface mount caps! I kept staring at the screen. Took a full minute of replays to actually see it. Amazing. Like those pictures where you can see the elephant in the moire if you keep studying...
I worked months ago on a 1963 Sharp BP-301 pocket radio and it had the same problem, this same insane gain and distorted sound, whistle everywhere when trynig to peak the tranformers, a total nightmare. So I started to change some resistors here and there and it started to do less noise, however still super sensitive. I changed the IFs transistors by very similar ones and worked great, maybe the old transistors was noisy who knows? And the last thing I did was to change the value of the avc resistor to get a perfect gain balance. Man, what you did was incredible, so tiny thingy. Thank you very much, this is amazing.
I discovered something. Never watch a radio alignment video when you have a headache. Makes head hurt a lot worse. But it’s still better than watching the news.
Coupling is ONLY via the top capacitor. The walls do NOT allow the em field through. 2.1pf makes sense, so does 21pf, NOT 260pf. Schematic should show the shield can dotted lines between the two coils. Not getting a peak probably means wrong value caps used. Note that the top cap will determine the bandwidth of the IF, and also flatten out the tuning if too large (coils will interact in tuning if top cap is too large). Motor boating is probably a bad bypass cap.
Philco was a big contractor to the US government for electronics, especially in satellite construction. They heavily invested in transistor technology for their work, something that passed down to Ford's automotive electronic fuel injection as those systems were designed and built to mil spec (with the odd exception of their ignition pickups which had high failure rate). Nice to hear Philco's old transistors are still good, and that their consumer goods were along the quality of what they put in their aerospace equipment.
I recognize this as my Dad's old "shaving radio". We lived very close to a Philco Plant in Sandusky Ohio. I often wondered if this radio was actually built there. All the Best! DE W8LV BILL
I don't think this is silver mica disease. It may be semantics, but I define SMD as metal migration on silver across the surface of the mica induce by high voltage (90 volts) attraction. The resulting leakage currents from plate of preceding stage to grid of succeding stage generally sounds like a lightning storm approaching. This radio did not have that sound. All I noticed was tarnishing of the silver surface, and suspect if you had polished with a pencil eraser and reassembled and tightened the clips the transformer woulda been good to go. I'm skeptical that transistor radios with their low voltages (>12 volts) will have enough attraction to cause the silver to migrate across the mica surface. I could be wrong on this point. I'm not sure if the two aluminum (nonmagnetic) cans will act as a faraday screen to electrostatically reduce high frequency coupling, while allowing lower frequency electromagnetic coupling. You have definitely noted too much RF gain. I had this trouble with a Zenith Royal 275. The .05 mf local oscillator coupling capacitor ( a disc ceramic) had turned into a 22 K resistor. Hard to believe but true. Check Beitman's Volume R-20 (1960), page 179. You will note C15 from LO coil to low end of antenna coil. Leaky cap raised base bias by about 1 volt. Radio still played, local stations had splattering audio. I have a Royal 450 that has a bad 2nd IF output transformer. The internal 250 pf cap went open. I tacked 2 100pf + a 50 pf across the tranformer and it tune right up, and had good sensitivity. After several months of use the radio died again. I had to unsolder the caps under the transformer. Apparently, tin whiskers formed joining the internal cap back in circuit, but with resistance in series. As such, the radio works now, but lacks sensitivity. I'm just not brave enough to do microsurgery on the transformer. It sits on the kitchen windowsill and plays talk radio. BTW, you are one tenacious mofo!
@@garbleduser That page # was for the Zenith Royal 275. Shango's T75-124 is in Bietman's 1959, page 105. His radio has an autodyne convertor (no separate local oscillator with coupling cap into mixer), so actually, I gave Shango some useless info. His radio apparently has no RF AGC, only IF AGC. I notice the detector is a transistor, prolly a detector and AGC amp. My only reccomendation is to check bias on RF, IF, and Det/AGC amp. If that uncovers nothing, try bridging a resistor from neg. side of C4 (AGC filter) to emitter of RF Amp. Maybe he could get some delayed AGC action going.
When that mica wafer came came out, it reminds me of a dentist when he does a root canal when he pulls out the root and he looks at it with a smile on his face and says to you " That didn't hurt you now did it ? "
The coupling I think mostly is through the 2.6pF cap. The aluminum shields probably act as pretty good shields at 455 kHz. There might be some magnetic coupling but I think they rely on the 2.6pF to do most of the coupling. You want to lightly couple the two halves to preserve good overall bandpass repsonse. If you ever look at double tuned (2 tank circuits) with a top coupling cap the top coupling cap is always pretty small. Also, those old style 2.6pF type ceramic caps are pretty reliable unless mechanically damaged.
Mica a very soft material to even place in an old Philco radio...........in the first place. I am staying away from extremely old radios with Silver Mica Waffles in them. I love religning old radios just for a fun pastime. An Excellent loud alignment noises from that Philco Radio.. Working on an old large 1970 Japanese "Silver" Boombox myself. RE-Winding a new S.W. and A.M. antenna for it. Nice old A.M. Philco Radio. I have to replace a mica tuning transformer in the tuning circuit, that I burnt with my soldering gun by mistake. Good Luck on your repairs there. Bye Now ! Maybe Connecting a sound generator to the back antenna section may help alignment not really sure ??..... When I was 8 years old, I did it to my old Radio Shack Citizen Radio, and it aligned perfectly. Spray that Frequency Turner box capacitor with some WD-40 maybe.....???? Mod it some how ??? It's to peak up and needs backing down a bit maybe in the gain. Could even be in the A.M. Ferrite antenna maybe ??? Crack-Co Box Radio.
I needed a video like this in the eighties, when I used to fix radios, kkkk. You are the best in this area, I loved your attentin to the details, keep going.
Congratulations Shango nice work. The gain was above average, the distortions in the sound must be some resistor with value changed in the rf step, but checking all is more guaranteed. But the master is you, always with new challenges. Hug.
I love that SMD stuff for experimenting at VHF and UHF, you can slap your circuit together any way you want (just keep it small) with no regards given to parasitics. It just works... But after a certain age, you need to work under a microscope with it
The IF capacitors are not that critical in value, once you are able to peak it, it should work. No way the motorboating could be caused by them. And the small 2.6pF is really that low, its value should be Ccoup = Ctune × BW / Fif /sqrt(2) = 160p × 10.5kHz / 455kHz /1.414 = 2.6pF. (Assume that LC pair is designed for flat top with the Q=60 of both LCs)
This^. It’s a double tuned circuit, capacitively coupled. The value of that cap affects the Q and coupling factor. A cheap spectrum analyzer would be well worth the money for this.
Great job, Shango066, on soldering those tiny surface mount caps! I'm sure I can no longer see well enough to do that little tiny work anymore! My hands are still steady, even though very arthritic, but my close vision is terrible for tiny things, even with magnification!🙃🙄
@@danmackintosh6325 The older I get the easier it becomes to listen to my gut. Partly because it has more to say for itself and partly because it appears to be the only part of me that isn't shrinking. ;~)
Wouldn't it be cool if the schematic indicated proper values for these in can mica capacitors. Guess the manufacturers figured the sets would not last long enough to require this repair. Thanks for another trinco-twinkulate tutorial, Shango! That radio is a classic...........
Back in the day it was presumed that if a component such as an interstage transformer failed you would order a replacement from the manufacturer. Nobody would attempt to fix those.
I had a radio like the one you are showing,when I moved all but some radios and players came with me but not that one it worked but it needed recapping to it but it worked but distorted sound.
I have one of these that sort of worked when I picked it up. While Turing the volume up, it stayed at one level until turned to 75%, then overdrove. After spraying the pot with cleaner, all it does is motorboat now. I suspect a bad transistor, but am trying to figure out how to test it w/o having to desolder.
I feel you. I live in Switzerland - there is exactly one physical store for electronic parts in the country (Zurich). Everything else is online. So if something is really exotic i might have to have it shipped from fricken Minnesota (Digikey).
maybe need to 'stagger tune' those IFs so bandwidth isnt so sharp, and that'll also reduce gain peak,, something like last IF 455, one of that pair 457 , other 452 ??? i've seen service info on some valve/tube sets state you should stagger tune their IFs ....? sometimes the manuals say you 'damp' one coil with a resistor while adjusting the other, then do opposite, also gives wider bandwidth and less sharp peak gain
I have a fat stupid.... Philco radio with silver mica disease. I still listen to it a little here and there. It's a model 51-1730 the kind people don't keep. I saved it from the dump. It sounds good even with the 6 or 8 inch speaker all of the way on the floor. Atop it sits my Philco electrostatic deflection 50-701 Bakelite TV. I guess I have to fix them both! Plus the phono with all of the dried up rubber parts. Wish me luck.
I’m sure that’s what happened. Radiotvphononut ties two capacitors (or resistors) together to get the correct value quite often. I’ve had to do it myself before.
I've done a lot of homrbrewing and prototying of superhet cw transceivers. I've replaced commercial Chebychev bandpass filters with one I built on a daughter board- which are basically what you have there with your two coupled IF cans.. and in my case- the capacitor coupling the two filter sections was SMALL shango.. always, always on the order of 2.7 to 3.3pf. Never more than 4.7.. and even that really broadens up the filter peak and flattens it
Puzzled over your mystery cap. 2.6pF would be red, blue, gold. 0.26pF would be red, blue, silver. Hard to see on the video exactly what that 3rd band colour is. Sometimes seems partly silver, other times just missing.
Are you sure your IF stage isn't oscillating? That tuning sounds like a regen that's been driven beyond the highest gain. Or a Hallicrafters S-120 with the "BFO" turned up. Cool circuit!
Didn't you have a similar problem on an Arvin set about a year ago? On both sets I would change the resistors on the feedback line and see what happens. You don't need to take the Philco apart for this as you can chop the resistors out and solder to the leads. Good Luck.... Unless these two sets are for use in weak areas?
Curious about the cap between the 2 transformers on the good radio. What value does it measure? Swap the 2 transformers from good to anti good... Hook up the fancy gear and get a visual on those signals.
Do you use a signal tracer to isolate what is causing the motorboat sounds since its clear its not the if coils that were recapped? Was this radio ever fixed?
Your SOKOL 403 has similar, capacitively coupled IF tanks. The SOKOL has 5.6pF intercoupling caps, but it has larger (510pF) caps in the IF tanks too. 2.7pF coupling is a good match for the 160pF IF tanks in this radio. The schematic is obviously wrong, that is a pair of capacitively coupled IF tanks, not a transformer. There is no inductive coupling between the two coils, they are totally shielded from each other by the aluminum can and the pot tuning cores that surround the coils.
The bandpass-filter is kind of 2 single resonant circuits with coupling-capacitor and no inductive coupling, there a some other possibilities to couple 2 resonant circuits, this is called "capacitive headpoint-coupling", "capacity footpoint-coupling" is common in some tv-sets between tuner and if-amp. Some kind of coupling can be seen here (german site): www.radiomuseum.org/forum/abgestimmbare_bandfilter_mit_konstanter_bandbreite.html 2 guesses about the motor-boating: If the capacitor in the AGC is open, if-amp may generate motorboating under strong signal because of no-linear processing with overdrive, then saturate, AGC brings signal down and overdrive again... sometimes you have 2 different AGC-circuits with 2 diodes to get rid of overdrive. .... second guess ist: For an if-alignment the front-end oscillator has to be quite (variable cap has to be shorted), because in this simple superhet-circuits the mixing stage is combined with the oscillator! (self-swinging-mixing-circuit). There can be strange effects under strong signal, too, if this stage is coupling with if-signal of high amplitude. "gain out of control" - this may cause the motorboating ! I think, it must be easy to find for you ! good work ^^
Literal translation of how soviet engineering tradition calls these bandpass LC networks is "concentrated selection filter" ("фильтр сосредоточенной селекции" or abbreviated "ФСС"). They used them extensively on most popular and on top of medium price range consumer receivers, especially on models with drum band switch as on tuners of old TV sets, but one can find them in even some smaller or pocket size radios. Soviets, as far as I know, never used mica wafers inside cans, so there never was such a problem with them. Some of the well known soviet receivers with rediculously complex IF filter networks were VEF-12, ~201 to ~206. Even more complicated were filters of Ocean models 209 to 216 and their export brand equivalens Selena with banks of 10 coils, 2 groups in paralel of 5 sequential for AM/FM that were not even switched but used the "magic" property of high and low friquencies not to "see" each other wile navigating LC networks.
Yep that's why the Soviet stuff is badass. Mostly just broken sodders and open capacitors. Never even played with the alignment on one and they kick the crap out of most other radios
Would a bad emitter bypass capacitor affect a collector current (let it run higher, as they are intended to provide negative feedback on collector current variance) and yield an increase in a stage gain?
26:00 I like those CONELRAD markers on the flip side of the dial with a separate pointer. Almost makes you wish for a nuclear war just to try them out.
That schematic is deceiving, it is not a transformer. There is not any inductive coupling. They are just tuned LC filter circuits coupled with a very low value capacitor. The coupling cap may even be .21pf as the silver band could be a .01 multiplier.
How about if the original Micah sheep was turned in the other direction where the black mark was not the point of contact maybe that would have done the trick
The problem is that you are peaking both coils to 455 kHz. You have to obtain more like an inverted U shape than an inverted V shape. You have to peak one coil to around 454 kHz, than the other coil to around 456 kHz, this is reducing the overall peak gain, but also assures a wide enough bandwidth for AM reception which also means less distortion. Keep in mind AM bandwidth is 10 kHz and you can't obtain such a large bandwidth by peaking both cans to 455 kHz. Your method of alignment is suitable for DX when want to obtain maximum performance in rural areas, but in some cases when the coils have high Q it is not suitable for distortion free reception, in such cases you have to detune one of the cans to obtain a higher bandwidth (some manufacturers add a 20-200k resistor across the coil to have a higher bandwidth, in this case you don't have to detune it).
Greetings: Since the core threads are very visible, can removing the core itself permit measuring the existing capacitor value permitting the closest SMT cap (size appropriate) to be placed in position and attached (or under pressure) as the original was before restoring the core? Gives you a place for a good capacitor. My best educated guess is that the 2.6pf cap is to couple the two tank circuits together passing the rf since the cans themselves cannot couple the inductors. I'm sure you will learn that other resonant tank circuits using similar cans have a distinct method of non-inductive coupling of circuits. I want to be sure not to forget to congratulate you for thinking of the additive affect of using a second cap to put the values in range of the component tester when looking for the value of the 2.6pf cap. AVC: can you compare the working of the two radio's AVC circuits to determine if they are different (even using the signal gen to establish the rf levels that create relevant levels).
That would kill the gain completely - there is the 1st if transistor bias voltage on it, so once it shorts out the gain is gone (the AGC just reduces that voltage). But the high ESR or too low capacitance means there becomes RF path back from the detector.
in tube radios ( hammarlund) the mica caps are leaves open to the atmosphere, and they routinely are found bad.. with a totally dead stage. removing them and installing outboard sealed mica caps is the cure. I have never tried compressing the coil in those much larger if cans.. this seems like a bad solder job.
Those are probably assembled and tuned separately using a spectrum analyzer. It supports another suggestion that the coils are tuned slightly off peak to widen the bandwidth and sharpen the skirts. Hard to do by “ear” as you don’t know the bandwidth you end up with. The extra gain and distortion (from filtering too much of the side bands) he experienced by peaking both seems to point that way.
11:35 На схеме четко видно что это две раздельные катушки . Каждая катушка со своей регулировкой и со своим сердечником обозначенными стрелкой в катушке. А пунктиром обведено для обозначения фильтра Z-1 У них не должно быть между собой индуктивной связи, иначе добротность контуров будет снижена. P.S. Perhaps I repeat someone's comments. To read all of them, I need to spend a lot of time ..))
Interesting how you manage to get -70 to -80 dB on the signal gen. I can't seem to ever get sensitivity better than -25, no matter what I do. Tried on MANY radios.
He was tapped into the radio with a small capacitor apparently in accordance to the service manual. I find the objective/instrument measurement to be very interesting. I have a B&K 2000-E with the attenuation switches. I find that cutting a few in usually knocks out my indications. I've only laid the test lead behind the radio. Not a good way to get results which can be duplicated. Let me know if you try anything new or do a video. Maybe we all can try and do a sensitivity test with some standard procedure. I have many books. The old Coyne books are great. Book 3, "Radio and Television Circuits," Chapter 5 "Receiver and Amplifier Performance," I have a marker on page 134 and Chapter 6, "Tests For Faulty Performance," I have a marker on page 150. This book is so much fun to dig into. It's an oddball orphan without it's other companion books, but I have complete set. It says 1955 Copyright 1957 Edition. Maybe we can try and do some tests in the same way. Different radios and test equipment and see how it comes out. Be well.
It's capacitively coupled NOT inductively coupled ..... The best way to determine the capacitor size would be to measure the inductance of the coil with the slug out (minimum inductance) and then turn the slug in to get maximum and then use whatever is halfway. Then just plug that inductance and 455Khz into a resonance calculator and you'll have your capacitance. Pick a value that is close to the calc (You hardly ever get a value that lands exactly on a common capacitance) and then use the slug to peak it. The coupling capacitor is an entirely different story because you need to find the "critical coupling" value (Keeps the passband flat with no dips and peaks) and that's hard to do without a sweep generator and a scope or a spectrum analyzer so you can see the passband
13:54 Holy crap! What a precise job of soldering those surface mount caps! I kept staring at the screen. Took a full minute of replays to actually see it. Amazing. Like those pictures where you can see the elephant in the moire if you keep studying...
I worked months ago on a 1963 Sharp BP-301 pocket radio and it had the same problem, this same insane gain and distorted sound, whistle everywhere when trynig to peak the tranformers, a total nightmare. So I started to change some resistors here and there and it started to do less noise, however still super sensitive. I changed the IFs transistors by very similar ones and worked great, maybe the old transistors was noisy who knows? And the last thing I did was to change the value of the avc resistor to get a perfect gain balance. Man, what you did was incredible, so tiny thingy. Thank you very much, this is amazing.
I discovered something. Never watch a radio alignment video when you have a headache.
Makes head hurt a lot worse.
But it’s still better than watching the news.
Coupling is ONLY via the top capacitor. The walls do NOT allow the em field through. 2.1pf makes sense, so does 21pf, NOT 260pf. Schematic should show the shield can dotted lines between the two coils. Not getting a peak probably means wrong value caps used. Note that the top cap will determine the bandwidth of the IF, and also flatten out the tuning if too large (coils will interact in tuning if top cap is too large). Motor boating is probably a bad bypass cap.
Correct, especially when cap ESR goes wrong, many NOS radio sets tend to moborboat when revived after a while...very common issue
Yes, Scharkalvin is %100 Correct. I think the coupling cap is 2.1 pf
Philco was a big contractor to the US government for electronics, especially in satellite construction. They heavily invested in transistor technology for their work, something that passed down to Ford's automotive electronic fuel injection as those systems were designed and built to mil spec (with the odd exception of their ignition pickups which had high failure rate). Nice to hear Philco's old transistors are still good, and that their consumer goods were along the quality of what they put in their aerospace equipment.
"It's gonna be very difficult to... uh, trinco-crinkulate the... eh spromulizer... with the deluplord all barmelcrinkler like it is."
I love you, man.
Is this an attempt to sound technical? Lol 😂
really
Man nothing stops you. These are TINY
I recognize this as my Dad's old "shaving radio". We lived very close to a Philco Plant in Sandusky Ohio. I often wondered if this radio was actually built there. All the Best! DE W8LV BILL
Incredible box of disc caps !
12:40 HAHAHAHAHAHAHAH if you have watched him for years this clip is the mojo of his humor. 45 mins!!!! 😂
A true master TV/radio technician. Always enjoy your work friend thank you.
Love the look of these old philcos. Thanks for the happy ending, shango.
I used a old Philco for my hobby of gathering QSL cards. Back in the 1970’s. Sunset skip was fun.
We need a t-shirt with your technology verbiage
Soldering skills on the surface mount capacitors. Good eyesight there.
I get my American news from your videos! (Off the radio)
I don't think this is silver mica disease. It may be semantics, but I define SMD as metal migration on silver across the surface of the mica induce by high voltage (90 volts) attraction. The resulting leakage currents from plate of preceding stage to grid of succeding stage generally sounds like a lightning storm approaching. This radio did not have that sound. All I noticed was tarnishing of the silver surface, and suspect if you had polished with a pencil eraser and reassembled and tightened the clips the transformer woulda been good to go. I'm skeptical that transistor radios with their low voltages (>12 volts) will have enough attraction to cause the silver to migrate across the mica surface. I could be wrong on this point. I'm not sure if the two aluminum (nonmagnetic) cans will act as a faraday screen to electrostatically reduce high frequency coupling, while allowing lower frequency electromagnetic coupling. You have definitely noted too much RF gain. I had this trouble with a Zenith Royal 275. The .05 mf local oscillator coupling capacitor ( a disc ceramic) had turned into a 22 K resistor. Hard to believe but true. Check Beitman's Volume R-20 (1960), page 179. You will note C15 from LO coil to low end of antenna coil. Leaky cap raised base bias by about 1 volt. Radio still played, local stations had splattering audio. I have a Royal 450 that has a bad 2nd IF output transformer. The internal 250 pf cap went open. I tacked 2 100pf + a 50 pf across the tranformer and it tune right up, and had good sensitivity. After several months of use the radio died again. I had to unsolder the caps under the transformer. Apparently, tin whiskers formed joining the internal cap back in circuit, but with resistance in series. As such, the radio works now, but lacks sensitivity. I'm just not brave enough to do microsurgery on the transformer. It sits on the kitchen windowsill and plays talk radio. BTW, you are one tenacious mofo!
Holy shyt... He referenced a page number... Shango, LOOK HERE!!!
@@garbleduser That page # was for the Zenith Royal 275. Shango's T75-124 is in Bietman's 1959, page 105. His radio has an autodyne convertor (no separate local oscillator with coupling cap into mixer), so actually, I gave Shango some useless info. His radio apparently has no RF AGC, only IF AGC. I notice the detector is a transistor, prolly a detector and AGC amp. My only reccomendation is to check bias on RF, IF, and Det/AGC amp. If that uncovers nothing, try bridging a resistor from neg. side of C4 (AGC filter) to emitter of RF Amp. Maybe he could get some delayed AGC action going.
Drift-omatic. Perfect.
When that mica wafer came came out, it reminds me of a dentist when he does a root canal when he pulls out the root and he looks at it with a smile on his face and says to you " That didn't hurt you now did it ? "
The 0603 and 0805 are the size of the components. I am an SMT operator and use parts like those every day.
The coupling I think mostly is through the 2.6pF cap. The aluminum shields probably act as pretty good shields at 455 kHz. There might be some magnetic coupling but I think they rely on the 2.6pF to do most of the coupling. You want to lightly couple the two halves to preserve good overall bandpass repsonse. If you ever look at double tuned (2 tank circuits) with a top coupling cap the top coupling cap is always pretty small. Also, those old style 2.6pF type ceramic caps are pretty reliable unless mechanically damaged.
ಅದ್ಭುತವಾದ ಸುಂದರವಾದ ವಿಡಿಯೋ ❤️😍 amazing and beautiful video ❤️🌹🙏
Mica a very soft material to even place in an old Philco radio...........in the first place. I am staying away from extremely old radios with Silver Mica Waffles in them. I love religning old radios just for a fun pastime. An Excellent loud alignment noises from that Philco Radio.. Working on an old large 1970 Japanese "Silver" Boombox myself. RE-Winding a new S.W. and A.M. antenna for it. Nice old A.M. Philco Radio. I have to replace a mica tuning transformer in the tuning circuit, that I burnt with my soldering gun by mistake. Good Luck on your repairs there. Bye Now ! Maybe Connecting a sound generator to the back antenna section may help alignment not really sure ??..... When I was 8 years old, I did it to my old Radio Shack Citizen Radio, and it aligned perfectly. Spray that Frequency Turner box capacitor with some WD-40 maybe.....???? Mod it some how ??? It's to peak up and needs backing down a bit maybe in the gain. Could even be in the A.M. Ferrite antenna maybe ??? Crack-Co Box Radio.
I needed a video like this in the eighties, when I used to fix radios, kkkk. You are the best in this area, I loved your attentin to the details, keep going.
I turned my fluorescent light off here in the UK and your Philco started motor-boating...
Co incidence. World is so Small.
Im in UK too. Wonder how many viewers he gets in the UK? As its mostly USA domestic products that weren't sold in Britain.
Congratulations Shango nice work.
The gain was above average, the distortions in the sound must be some resistor with value changed in the rf step, but checking all is more guaranteed. But the master is you, always with new challenges.
Hug.
12:41 . . . "I've been digging through this for the past 45 minutes."
You have just "a few" disc capacitors on hand!!
I love that SMD stuff for experimenting at VHF and UHF, you can slap your circuit together any way you want (just keep it small) with no regards given to parasitics. It just works... But after a certain age, you need to work under a microscope with it
The IF capacitors are not that critical in value, once you are able to peak it, it should work. No way the motorboating could be caused by them.
And the small 2.6pF is really that low, its value should be Ccoup = Ctune × BW / Fif /sqrt(2) = 160p × 10.5kHz / 455kHz /1.414 = 2.6pF. (Assume that LC pair is designed for flat top with the Q=60 of both LCs)
This^. It’s a double tuned circuit, capacitively coupled. The value of that cap affects the Q and coupling factor. A cheap spectrum analyzer would be well worth the money for this.
Oh boy, another video I haven't seen until now. 👍
Fun and educational!
Great job, Shango066, on soldering those tiny surface mount caps! I'm sure I can no longer see well enough to do that little tiny work anymore! My hands are still steady, even though very arthritic, but my close vision is terrible for tiny things, even with magnification!🙃🙄
Very interesting video..l love radio device's... thanks.
11:58 if the tincans are groundulated then the couplification can only be made with the capcifier. I hope this helps with the lerndification process.
@shango066 here's what my gut told me too... Also, @Andrew Hull that comment reads a lot like a cross between Shango066 and Vice Grip Garage
@@danmackintosh6325 The older I get the easier it becomes to listen to my gut. Partly because it has more to say for itself and partly because it appears to be the only part of me that isn't shrinking. ;~)
@@danmackintosh6325 There was a VGG flavor in there lol
Wouldn't it be cool if the schematic indicated proper values for these in can mica capacitors. Guess the manufacturers figured the sets would not last long enough to require this repair. Thanks for another trinco-twinkulate tutorial, Shango! That radio is a classic...........
Back in the day it was presumed that if a component such as an interstage transformer failed you would order a replacement from the manufacturer. Nobody would attempt to fix those.
It's such a good looking radio, I'd just set it on the shelf and admire the petina...
I had a radio like the one you are showing,when I moved all but some radios and players came with me but not that one it worked but it needed recapping to it but it worked but distorted sound.
Hmm a tight 455 filter, the small coupling cap is the path between coils.
Those small component meter are useful. I use mine to measure my capacitors.
That's a good candidate to test in the next desert trip,maybe do a comparison between the two of them.Interesting fault,that's for sure!
The sticker inside the back cover of the radio said leak proof D cells, but you put in Duracells...
Duracells are the worst, I won't even have them in my house. They have leaked too many times on me.
I have one of these that sort of worked when I picked it up. While Turing the volume up, it stayed at one level until turned to 75%, then overdrove. After spraying the pot with cleaner, all it does is motorboat now. I suspect a bad transistor, but am trying to figure out how to test it w/o having to desolder.
It is what it is , old electronics are fascinating, replacing the high resistors would help . I believe.
At least you have a local parts store. All of them in my area are gone.
I feel you. I live in Switzerland - there is exactly one physical store for electronic parts in the country (Zurich). Everything else is online. So if something is really exotic i might have to have it shipped from fricken Minnesota (Digikey).
maybe need to 'stagger tune' those IFs so bandwidth isnt so sharp, and that'll also reduce gain peak,, something like last IF 455, one of that pair 457 , other 452 ??? i've seen service info on some valve/tube sets state you should stagger tune their IFs ....? sometimes the manuals say you 'damp' one coil with a resistor while adjusting the other, then do opposite, also gives wider bandwidth and less sharp peak gain
Many radios using germenium tr. Internal capacitance, in i. f. amp. feedback is so high that stager tuning is ony way to stable this stage.
Truth! I would peak them both and then turn them a fraction in opposite directions to achieve the same.
Good luck sir 🎉
What are the odds that the same day I'm working on a TV with silver mica disease, you upload a video about silver mica disease
I have a fat stupid.... Philco radio with silver mica disease. I still listen to it a little here and there. It's a model 51-1730 the kind people don't keep. I saved it from the dump. It sounds good even with the 6 or 8 inch speaker all of the way on the floor. Atop it sits my Philco electrostatic deflection 50-701 Bakelite TV. I guess I have to fix them both! Plus the phono with all of the dried up rubber parts. Wish me luck.
I noticed the ball bearings were not rolling on the tuning capacitor shaft, as you were tuning.
Beautiful design..What happened to the world?
Sometimes the reason is that they ran out of the correct part and used what they had on the shelf.
Yes 👍🏼 I could see that happening.
I’m sure that’s what happened. Radiotvphononut ties two capacitors (or resistors) together to get the correct value quite often. I’ve had to do it myself before.
hi sometimes volume's variable resistance requires cleaning it my ca
uses noise
3:33 it could be a bad solder connection by the looks of it, but that may look that way because of the blurriness.
I've done a lot of homrbrewing and prototying of superhet cw transceivers. I've replaced commercial Chebychev bandpass filters with one I built on a daughter board- which are basically what you have there with your two coupled IF cans.. and in my case- the capacitor coupling the two filter sections was SMALL shango.. always, always on the order of 2.7 to 3.3pf. Never more than 4.7.. and even that really broadens up the filter peak and flattens it
Exactly, otherwise you adversely disturb the passband response and Q not to mention loading of the amplifiers.
Great 👍 video very interesting love watching your repair videos plus when you said i hear it howling i thought you meant the film the howling ha ha
Puzzled over your mystery cap. 2.6pF would be red, blue, gold. 0.26pF would be red, blue, silver. Hard to see on the video exactly what that 3rd band colour is. Sometimes seems partly silver, other times just missing.
Are you sure your IF stage isn't oscillating? That tuning sounds like a regen that's been driven beyond the highest gain. Or a Hallicrafters S-120 with the "BFO" turned up. Cool circuit!
I second this.
Didn't you have a similar problem on an Arvin set about a year ago? On both sets I would change the resistors on the feedback line and see what happens. You don't need to take the Philco apart for this as you can chop the resistors out and solder to the leads. Good Luck.... Unless these two sets are for use in weak areas?
Yes. I'm pretty sure it's a transistor
Curious about the cap between the 2 transformers on the good radio. What value does it measure? Swap the 2 transformers from good to anti good... Hook up the fancy gear and get a visual on those signals.
A zip tie holding a spring would have been an easy fix.
Do you use a signal tracer to isolate what is causing the motorboat sounds since its clear its not the if coils that were recapped? Was this radio ever fixed?
Your SOKOL 403 has similar, capacitively coupled IF tanks. The SOKOL has 5.6pF intercoupling caps, but it has larger (510pF) caps in the IF tanks too. 2.7pF coupling is a good match for the 160pF IF tanks in this radio.
The schematic is obviously wrong, that is a pair of capacitively coupled IF tanks, not a transformer. There is no inductive coupling between the two coils, they are totally shielded from each other by the aluminum can and the pot tuning cores that surround the coils.
The bandpass-filter is kind of 2 single resonant circuits with coupling-capacitor and no inductive coupling, there a some other possibilities to couple 2 resonant circuits, this is called "capacitive headpoint-coupling", "capacity footpoint-coupling" is common in some tv-sets between tuner and if-amp.
Some kind of coupling can be seen here (german site): www.radiomuseum.org/forum/abgestimmbare_bandfilter_mit_konstanter_bandbreite.html
2 guesses about the motor-boating: If the capacitor in the AGC is open, if-amp may generate motorboating under strong signal because of no-linear processing with overdrive, then saturate, AGC brings signal down and overdrive again... sometimes you have 2 different AGC-circuits with 2 diodes to get rid of overdrive. .... second guess ist: For an if-alignment the front-end oscillator has to be quite (variable cap has to be shorted), because in this simple superhet-circuits the mixing stage is combined with the oscillator! (self-swinging-mixing-circuit). There can be strange effects under strong signal, too, if this stage is coupling with if-signal of high amplitude.
"gain out of control" - this may cause the motorboating ! I think, it must be easy to find for you !
good work ^^
Literal translation of how soviet engineering tradition calls these bandpass LC networks is "concentrated selection filter" ("фильтр сосредоточенной селекции" or abbreviated "ФСС"). They used them extensively on most popular and on top of medium price range consumer receivers, especially on models with drum band switch as on tuners of old TV sets, but one can find them in even some smaller or pocket size radios. Soviets, as far as I know, never used mica wafers inside cans, so there never was such a problem with them. Some of the well known soviet receivers with rediculously complex IF filter networks were VEF-12, ~201 to ~206. Even more complicated were filters of Ocean models 209 to 216 and their export brand equivalens Selena with banks of 10 coils, 2 groups in paralel of 5 sequential for AM/FM that were not even switched but used the "magic" property of high and low friquencies not to "see" each other wile navigating LC networks.
Yep that's why the Soviet stuff is badass. Mostly just broken sodders and open capacitors. Never even played with the alignment on one and they kick the crap out of most other radios
Would a bad emitter bypass capacitor affect a collector current (let it run higher, as they are intended to provide negative feedback on collector current variance) and yield an increase in a stage gain?
26:00 I like those CONELRAD markers on the flip side of the dial with a separate pointer. Almost makes you wish for a nuclear war just to try them out.
We have a station here on 1240. Never heard anything on 640.
20:00. Variable ganged caps are the same size.
Is this a TRF and not a superhet?
Gang cap. is not same sized. One side has one plate less. It is super hetrodyne.
Those transistor testers can read in single digit pF, you have to update the firmware and upgrade the crystal.
With it being super hot, you oughta carry it out to the desert, like you did with some other radios in a past video.
Once he fixes it he can make a custom modification and see if he can get some super DX out of 7 transistor portable.
Is that weird or what? I'm at 10 mins in. They do not look like transformers at all just two coils capacitively coupled?
That schematic is deceiving, it is not a transformer. There is not any inductive coupling. They are just tuned LC filter circuits coupled with a very low value capacitor. The coupling cap may even be .21pf as the silver band could be a .01 multiplier.
@ 3:20...........its the perfect cell song!!! XD
Maybe theres a transistor that’s gone bad. Since you mentioned that it sounds overdriven.
That’s what I’m thinking.
How about if the original Micah sheep was turned in the other direction where the black mark was not the point of contact maybe that would have done the trick
The problem is that you are peaking both coils to 455 kHz. You have to obtain more like an inverted U shape than an inverted V shape. You have to peak one coil to around 454 kHz, than the other coil to around 456 kHz, this is reducing the overall peak gain, but also assures a wide enough bandwidth for AM reception which also means less distortion. Keep in mind AM bandwidth is 10 kHz and you can't obtain such a large bandwidth by peaking both cans to 455 kHz. Your method of alignment is suitable for DX when want to obtain maximum performance in rural areas, but in some cases when the coils have high Q it is not suitable for distortion free reception, in such cases you have to detune one of the cans to obtain a higher bandwidth (some manufacturers add a 20-200k resistor across the coil to have a higher bandwidth, in this case you don't have to detune it).
Greetings:
Since the core threads are very visible, can removing the core itself permit measuring the existing capacitor value permitting the closest SMT cap (size appropriate) to be placed in position and attached (or under pressure) as the original was before restoring the core? Gives you a place for a good capacitor.
My best educated guess is that the 2.6pf cap is to couple the two tank circuits together passing the rf since the cans themselves cannot couple the inductors. I'm sure you will learn that other resonant tank circuits using similar cans have a distinct method of non-inductive coupling of circuits.
I want to be sure not to forget to congratulate you for thinking of the additive affect of using a second cap to put the values in range of the component tester when looking for the value of the 2.6pf cap.
AVC: can you compare the working of the two radio's AVC circuits to determine if they are different (even using the signal gen to establish the rf levels that create relevant levels).
Good Job! Congratulation.
hi mr. dan who do you do fin
can you just clean off the oxide and put them back?
I wonder where is the cantonese station come from
Is it possible to clean up the original mica caps and put them back in the I.F. cans?
4:45 WTF a are you on about chap? Lol 😂
Did the AGC elec. capacitor get installed backwards by chance??
That would kill the gain completely - there is the 1st if transistor bias voltage on it, so once it shorts out the gain is gone (the AGC just reduces that voltage). But the high ESR or too low capacitance means there becomes RF path back from the detector.
Interesting alien IF transformer
Clever ending.
in tube radios ( hammarlund) the mica caps are leaves open to the atmosphere, and they routinely are found bad.. with a totally dead stage. removing them and installing outboard sealed mica caps is the cure. I have never tried compressing the coil in those much larger if cans.. this seems like a bad solder job.
Ohhhh how I love Radio reciver specially old transistors Radio . Now we have no . Bcz the mp3 and all modern inventions
26:09 I don't understand why you're always talking about motorboats, when you have all these fancy moto-aeroplanes around? :D
Put a 1/4” jack on it and you have a germanium fuzz pedal for guitar!
12:52 That sounds like some obscure early-'90s rap record.
That's weird they stashed a resistor under the transformers must of been hurting for room
*must've
Must have been coupling capacitor.
Those are probably assembled and tuned separately using a spectrum analyzer. It supports another suggestion that the coils are tuned slightly off peak to widen the bandwidth and sharpen the skirts. Hard to do by “ear” as you don’t know the bandwidth you end up with. The extra gain and distortion (from filtering too much of the side bands) he experienced by peaking both seems to point that way.
The ASCEL LC meter kit (AE20204 from Germany) will measure “very” low pF caps .. it’s not expensive …
There the double stacked caps in series?
Parallel, apparently....
I don't think I've ever run into that problem with a transistor radio before.
11:35 На схеме четко видно что это две раздельные катушки . Каждая катушка со своей регулировкой и со своим сердечником обозначенными стрелкой в катушке. А пунктиром обведено для обозначения фильтра Z-1 У них не должно быть между собой индуктивной связи, иначе добротность контуров будет снижена.
P.S. Perhaps I repeat someone's comments. To read all of them, I need to spend a lot of time ..))
We benefit from the OCD in regard to getting this radio up and running.
Interesting how you manage to get -70 to -80 dB on the signal gen. I can't seem to ever get sensitivity better than -25, no matter what I do. Tried on MANY radios.
He was tapped into the radio with a small capacitor apparently in accordance to the service manual.
I find the objective/instrument measurement to be very interesting. I have a B&K 2000-E with the attenuation switches. I find that cutting a few in usually knocks out my indications. I've only laid the test lead behind the radio. Not a good way to get results which can be duplicated. Let me know if you try anything new or do a video. Maybe we all can try and do a sensitivity test with some standard procedure. I have many books. The old Coyne books are great. Book 3, "Radio and Television Circuits," Chapter 5 "Receiver and Amplifier Performance," I have a marker on page 134 and Chapter 6, "Tests For Faulty Performance," I have a marker on page 150. This book is so much fun to dig into. It's an oddball orphan without it's other companion books, but I have complete set. It says 1955 Copyright 1957 Edition. Maybe we can try and do some tests in the same way. Different radios and test equipment and see how it comes out. Be well.
It's capacitively coupled NOT inductively coupled ..... The best way to determine the capacitor size would be to measure the inductance of the coil with the slug out (minimum inductance) and then turn the slug in to get maximum and then use whatever is halfway. Then just plug that inductance and 455Khz into a resonance calculator and you'll have your capacitance. Pick a value that is close to the calc (You hardly ever get a value that lands exactly on a common capacitance) and then use the slug to peak it. The coupling capacitor is an entirely different story because you need to find the "critical coupling" value (Keeps the passband flat with no dips and peaks) and that's hard to do without a sweep generator and a scope or a spectrum analyzer so you can see the passband
you need to hire an intern to sort that box of disc capacitors
typical.. the silver corrodes(tarnishes) and the value changes. remove the leaf, and use outboard caps. works every time
Well done! Fun! Thank you.
4:34 What language is he speaking?
on the large scale hammarlunds. I do micro surgery and take them apart.
That cap is leako'matic the multimeter compensates the leakage.