Thanks for the informative video. Just did this repair on my 1960s Canadian Sparton 6 tube AM/FM. Working well with 129 Volts B plus with a 75 ohm resistor.
Thank you Shango066 - I was able to get an old Pilot FM converter to work with my low understanding of how radios work. I got the DC voltage up from about 50 to 110 with a diode, then I changed out the electrolytics, it worked but really poorly. Then I pulled the tubes out, sprayed the sockets and replaced them, now it works OK, gets a lot of stations but sounds farty. I think it needs more caps, but I am on the right track.
Great video! Selenium rectifiers and dial restringing are my pet peeves of repairs. Someday, I'd like to see you do a video of a tube battery/AC radio where the selenium is especially tricky to replace as the series filament voltage is tapped from the selenium rather than directly from the AC line. These can be a headache to calculate the value of the dropping resistor.
In a case like that you could calculate/estimate the voltage drop in the selenium (about 1 to 1.2v per plate) and more or less replicate it by building a string of silicon diodes at 0.7V drop each. If you need a tap, just find the place in the string that gives you what you need. No resistors needed. This plan does work best with the 4 to 7 plate seleniums, but if need be you could even do something with bigger ones.
4007's will work on some radios as a detector but only as a temporary fix. It should be replaced. I remember back when I was a kid building AM radios with 4007's (and other types) because the proper diodes were rare for me to get a hold of. Speaking of selenium rectifiers.. I just restored / rebuilt an old 1960's era variable bench power supply that had 4 of those things to make up a full bridge rectifier. I just replaces them with a modern bridge and gave it a new lease on life.
Replaced the SE rect in my Zenith AM-FM radio with a silicon diode but the voltage fluctuated with the audio when the volume was turned up using a series resistor. Ended up installing two power resistors in a voltage divider config to get a more stable B+ and now the voltage barely changes no matter where the volume is set. Thanks for the video.
That decade box is sweet, I need to get one of those. If the selenium rectifier is really far gone, sometimes I'll bridge a 1N4007 in there long enough to do diagnostics and get workable B+ readings. I've had some that outputted less than 60 volts.
Just FYI bridging a good part with a bad isn't the way to go IMHO , even temporarily. I know some have bridged almost shorted caps thinking it was ok to do. Really you are bridging a good cap with a shorted cap. The result is still going to be performing as if that cap was still shorted. Same with the Si diode across a bad Selenium. Why put a good part across the bad, even temporarily? You can do as you wish, however the few seconds it takes to disconnect the Selenium, and tack in a diode with a default resistance is well worth it. No worries about the Selenium failing, it's out of the circuit. Go ahead and replace the other caps, as you wish, then adjust the final B+. Just a thought.
Thanks for the tutorial, I have a couple of radios with bad ones in them. I wish I had a power decade box, I only have a standard low wattage decade box. I'm going to get a bunch of power resistors at different values for doing this.
Could I ask for some advice. There is a lot of confusion regarding the rectifier on old Villers motorcycles and how to replace them with a modern solid state rec. If you google up Villiers 2T engine wiring you will see what I mean but basically there are two ac coils one coil is connected all the time to the rec and the other is only connected throught the lighting switch when the lights are on. So two coils is series black wire common to both coils one red wire one green wire. No problem so far however half way across the coil with the red and black wires there is another yellow wire that goes to the ammeter to the battery. The question is what is this wire for know one seems to know why it was fitted. Its either supplying the ammeter with an AC supply but thats DC to the battery or the coil is getting a 6 volt dc supply. Any ideas dose the old type rec need a dc to work. The bikes were made in 1964.
Perfect timing...I have to change out a selenium rectifier. ( Fire Department on speed dial!) Question: How do you determine the wattage of the resistor used in series with the diode? Thanks!
Greetings: Since the B+ voltage varies with the volume setting, I would use the schematic 50 ma value as a starting point and measure ma as you select a resistor. Remember you have the option to use an electrolytic dropping cap whose 60Hz reactance equals whatever resistor you settle on (save a watt, save a penny). I know that you never use dropping caps, but you could learn. It goes between diode cathode and first filter cap +. Cap value is 29.4 mfd at 200v.
I a old Radio Shack Tube SAF-24 amp that has the same layout as this one with with one red wire going to ground and the other going to the Selenium with a 30ma draw, but when I replace the Selenium with a IN4007 diode the problem is my transformer is overheating now! It is acting like it is a shorted and it is . Any help please
I'm having the same issue with a Motorola 5R1. Its over heating after powering on. Is there a way to suppress the power spike from the diode until it warms up and the voltage drops?
Carl I did, I put a 100ohm 10 watt ceramic resistor that initially tested at 115.8v DC after warming up. Now the resistor after the rectifier and right before the filter caps is overheating badly when powered on. Would a thermistor help here?
doing this myself on an old 1-tube record player, and yes the volTage does jump around a bit. Coincidentally, I am using 71 ohms, but will swap that out for a 75 ohm resistor in a higher wattage.
Using that rectifier as a detector diode will cost you some sensitivity. Strong stations probably won't improve but weak stations should improve. You should look at what diodes are being used in the FM detection circuit. Change to recommended detector diodes.
I personally would not use a 1N4000 series as a detector. The Chinese Silicon Schottky's are probably the the best choice, since Germanium diodes are getting scarce and pricey these days. Then there is the long term reliability and leakage of Ge.
Never seen a Power Resistor Decade Box before. I looked them up on ebay. They are all 240-c models, prices range from $245-450. That's one pricey piece of equipment.
![Seungmin "그렇게, 천천히, 우리(As we are)" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/kAzmhLHePqU/mqdefault.jpg)
So cool to be there when YOU learned something new. Love your videos.
Patrick Barnes holy hell its P. Barnes!
After watching your Sears Suburbanite video a few years ago, I now call selenium diodes 'selenium squeebly zeeblers' every blasted time I see one.
Thanks for the informative video. Just did this repair on my 1960s Canadian Sparton 6 tube AM/FM. Working well with 129 Volts B plus with a 75 ohm resistor.
Thank you Shango066 - I was able to get an old Pilot FM converter to work with my low understanding of how radios work. I got the DC voltage up from about 50 to 110 with a diode, then I changed out the electrolytics, it worked but really poorly. Then I pulled the tubes out, sprayed the sockets and replaced them, now it works OK, gets a lot of stations but sounds farty. I think it needs more caps, but I am on the right track.
Great video! Selenium rectifiers and dial restringing are my pet peeves of repairs. Someday, I'd like to see you do a video of a tube battery/AC radio where the selenium is especially tricky to replace as the series filament voltage is tapped from the selenium rather than directly from the AC line. These can be a headache to calculate the value of the dropping resistor.
In a case like that you could calculate/estimate the voltage drop in the selenium (about 1 to 1.2v per plate) and more or less replicate it by building a string of silicon diodes at 0.7V drop each. If you need a tap, just find the place in the string that gives you what you need. No resistors needed. This plan does work best with the 4 to 7 plate seleniums, but if need be you could even do something with bigger ones.
4007's will work on some radios as a detector but only as a temporary fix. It should be replaced. I remember back when I was a kid building AM radios with 4007's (and other types) because the proper diodes were rare for me to get a hold of.
Speaking of selenium rectifiers.. I just restored / rebuilt an old 1960's era variable bench power supply that had 4 of those things to make up a full bridge rectifier. I just replaces them with a modern bridge and gave it a new lease on life.
Replaced the SE rect in my Zenith AM-FM radio with a silicon diode but the voltage fluctuated with the audio when the volume was turned up using a series resistor. Ended up installing two power resistors in a voltage divider config to get a more stable B+ and now the voltage barely changes no matter where the volume is set. Thanks for the video.
That decade box is sweet, I need to get one of those. If the selenium rectifier is really far gone, sometimes I'll bridge a 1N4007 in there long enough to do diagnostics and get workable B+ readings. I've had some that outputted less than 60 volts.
Just FYI bridging a good part with a bad isn't the way to go IMHO , even temporarily. I know some have bridged almost shorted caps thinking it was ok to do. Really you are bridging a good cap with a shorted cap. The result is still going to be performing as if that cap was still shorted.
Same with the Si diode across a bad Selenium. Why put a good part across the bad, even temporarily? You can do as you wish, however the few seconds it takes to disconnect the Selenium, and tack in a diode with a default resistance is well worth it. No worries about the Selenium failing, it's out of the circuit. Go ahead and replace the other caps, as you wish, then adjust the final B+. Just a thought.
Thanks for the tutorial, I have a couple of radios with bad ones in them. I wish I had a power decade box, I only have a standard low wattage decade box. I'm going to get a bunch of power resistors at different values for doing this.
Could I ask for some advice. There is a lot of confusion regarding the rectifier on old Villers motorcycles and how to replace them with a modern solid state rec. If you google up Villiers 2T engine wiring you will see what I mean but basically there are two ac coils one coil is connected all the time to the rec and the other is only connected throught the lighting switch when the lights are on. So two coils is series black wire common to both coils one red wire one green wire. No problem so far however half way across the coil with the red and black wires there is another yellow wire that goes to the ammeter to the battery. The question is what is this wire for know one seems to know why it was fitted. Its either supplying the ammeter with an AC supply but thats DC to the battery or the coil is getting a 6 volt dc supply. Any ideas dose the old type rec need a dc to work. The bikes were made in 1964.
Dam nice job,if it was me I always like old parts tossed,like the selium rectifier,,but it plays great.
Perfect timing...I have to change out a selenium rectifier. ( Fire Department on speed dial!) Question: How do you determine the wattage of the resistor used in series with the diode? Thanks!
Why do you need a capacitor in series with the diode? Do I miss something?
Yes.
Greetings:
Since the B+ voltage varies with the volume setting, I would use the schematic 50 ma value as a starting point and measure ma as you select a resistor. Remember you have the option to use an electrolytic dropping cap whose 60Hz reactance equals whatever resistor you settle on (save a watt, save a penny). I know that you never use dropping caps, but you could learn. It goes between diode cathode and first filter cap +. Cap value is 29.4 mfd at 200v.
Very cool! I just "won" a Philco E670 with a pretty blue selenium wonder. Wanna bet it's good or bad, built in 1957.
I a old Radio Shack Tube SAF-24 amp that has the same layout as this one with with one red wire going to ground and the other going to the Selenium with a 30ma draw, but when I replace the Selenium with a IN4007 diode the problem is my transformer is overheating now! It is acting like it is a shorted and it is . Any help please
I'm having the same issue with a Motorola 5R1. Its over heating after powering on. Is there a way to suppress the power spike from the diode until it warms up and the voltage drops?
@@mrvaportrailz did place a power dropping resistor in line? If not do so.
Carl I did, I put a 100ohm 10 watt ceramic resistor that initially tested at 115.8v DC after warming up. Now the resistor after the rectifier and right before the filter caps is overheating badly when powered on. Would a thermistor help here?
doing this myself on an old 1-tube record player, and yes the volTage does jump around a bit. Coincidentally, I am using 71 ohms, but will swap that out for a 75 ohm resistor in a higher wattage.
You found the AM detector on the chinese hx108 did not benefit from a Schottky. They had used a BJT NPN base to emitter I think.
Using that rectifier as a detector diode will cost you some sensitivity. Strong stations probably won't improve but weak stations should improve. You should look at what diodes are being used in the FM detection circuit. Change to recommended detector diodes.
Blondie Never Sounded Better!
EXCELLENT JOB
If you ever find a Silvertone 3068, I want to see it.
@6:30 - NOOO!!!!! Not that damn Nay nay crap lol
Muito bom, gostei. Parabéns pelo vídeo!
I personally would not use a 1N4000 series as a detector. The Chinese Silicon Schottky's are probably the the best choice, since Germanium diodes are getting scarce and pricey these days. Then there is the long term reliability and leakage of Ge.
strangely, in all my years I have never encountered a failed selenium rectumfire.
I see the camera really likes Blonde
Thank you!
Thank....You...For...Sharing.....Beep. :)
Yay Mr. Bobby is back! Happy New Years sir!
+Steven King Hey Steven. Happy new year right back at you and yours. :)
Replace that electrolytic on the left on the tube side since you're there.
Music to re-cap by...bootylicious
uncle Doug does this too~
Never seen a Power Resistor Decade Box before. I looked them up on ebay.
They are all 240-c models, prices range from $245-450. That's one pricey piece of equipment.
One of those things where it might be cheaper to build your own.
Shango can fix anything.
Hell yea, if I could take a current reading and apply Ohm's law I'd be an engineer instead of a hobbyist. (smile)
That was hot
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