Powers in Circuit (or other catchy names for after hours bars in Palo Alto)

Thread Starter

AirScooter

Joined Mar 23, 2021
6
Hi Folks,
I bought an old phonograph at an estate sale last week. It was really out of sorts, part of a grab bag I bought for three dollars. I wasn't expecting much, just thought I could pick a couple of circuits up to practice on.
The phono at the center of this post had had its entire component cadre remove. There was nothing under the table but the tube sockets. The tubes where there but that was about all. One was a 50L6GT and the other was a 35Z5GT.
I found the schematic and looked at what was missing. There was a 500K resistor, a 40 "MF" Cap and two 20 "MF" Caps and a lot more various bits and pieces and their connection to the tubes and beyond.
In the middle of my perusal and my subsequent realization that once again I was about to embark on another journey aboard the Good Ship BOM with my shipmate Ensign Digikey, I realized that I didn't know how to order components from a schematic that only offered each one's value without any notation about what power they needed to be. I had that all too familiar feeling that the lack of experience that has plagued my every step in this addiction was once again rearing it ugly head. Why, I again queried myself, had I not studied Electronic Engineering and not Social Engineering. I secretly knew the answer to that haunted question but had a hard time articulating it..... the secret was....I had a hard time adding 2+2 and coming up with a number close to four.
So.......Just how do you order missing components without their power indicated on the schematic? Just to be clear: I see each components value, but no indication of the power they need. If the answer is beyond 4 please explain slowly.
As so many have said before me ...... Thanks for your help!
Dave Lowa
 
Hello there! :) an extra pair of eyes are always helpful. Could you possibly take a photo of the unit. Both sides of the PCB.
The schematic as well if possible.
So we may have a reference on which to guide you through the process of identification of the components values and what they represent. Make and model of the unit if possible. Thank you.
 

Thread Starter

AirScooter

Joined Mar 23, 2021
6
Hi Folks,
I bought an old phonograph at an estate sale last week. It was really out of sorts, part of a grab bag I bought for three dollars. I wasn't expecting much, just thought I could pick a couple of circuits up to practice on.
The phono at the center of this post had had its entire component cadre remove. There was nothing under the table but the tube sockets. The tubes where there but that was about all. One was a 50L6GT and the other was a 35Z5GT.
I found the schematic and looked at what was missing. There was a 500K resistor, a 40 "MF" Cap and two 20 "MF" Caps and a lot more various bits and pieces and their connection to the tubes and beyond.
In the middle of my perusal and my subsequent realization that once again I was about to embark on another journey aboard the Good Ship BOM with my shipmate Ensign Digikey, I realized that I didn't know how to order components from a schematic that only offered each one's value without any notation about what power they needed to be. I had that all too familiar feeling that the lack of experience that has plagued my every step in this addiction was once again rearing it ugly head. Why, I again queried myself, had I not studied Electronic Engineering and not Social Engineering. I secretly knew the answer to that haunted question but had a hard time articulating it..... the secret was....I had a hard time adding 2+2 and coming up with a number close to four.
So.......Just how do you order missing components without their power indicated on the schematic? Just to be clear: I see each components value, but no indication of the power they need. If the answer is beyond 4 please explain slowly.
As so many have said before me ...... Thanks for your help!
Dave Lowa
Thank you for your reply Delta. I am not near the unit at the moment. I will send along photos as soon as I am near it again.
Thank you,
Dave Lowa
 

Thread Starter

AirScooter

Joined Mar 23, 2021
6
Hello there! :) an extra pair of eyes are always helpful. Could you possibly take a photo of the unit. Both sides of the PCB.
The schematic as well if possible.
So we may have a reference on which to guide you through the process of identification of the components values and what they represent. Make and model of the unit if possible. Thank you.
Here's the picture of what I got. (empty circuit) I have the schematic which indicates the component values but not the power for the individual components. I believe I read someplace that as a rule of thumb you can double the input voltage and use that as the voltage for each piece. I dunno, I'm sure it might work, it just feels like way over kill.
 

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Thread Starter

AirScooter

Joined Mar 23, 2021
6
Here's the picture of what I got. (empty circuit) I have the schematic which indicates the component values but not the power for the individual components. I believe I read someplace that as a rule of thumb you can double the input voltage and use that as the voltage for each piece. I dunno, I'm sure it might work, it just feels like way over kill.
The phonograph is a Televox, I don't have the model number but I think it is one of their "Junior Jukebox models.
Dave Lowa
 
OK, itlooks like somebody may have been intending to restore it. The circuit is very simple, since all that you have is a rectifier and a one tube amplifier. The first challenge will be the tubes. DigiKey does not sell those tubes, they have been obsolete since before 1960. So you will need to locate a purveyer of old tubes. Really, if you can get hold of an RCA receiving tube manual from the sixties it will have better but similar circuits, and much better descriptions of the components.
That amplifier is a marginal performer, but it did sort of work.
For the components, all capacitors should be rated at 150 working volts, and the resistors should be half watt rated, except for the one in series with the tube heaters.That should be at least 5 watts, I think. That resistor will be dropping 35 volts at the heater current, which it is 150 mA .
The 50L6 is the amplifier, the 35Z5 is the half wave rectifier. If the motor has three leads then it was used as a step-down transformer, and the project will be really interesting.
Look at the speaker, it has a transformer mounted on it, with red and blue wires. That is the audio output transformer. Not much iron and so it can not handle much audio power.
Probably the dual capacitor will be leaky and draw excessive current and so there will be hum along with the music. Modern replacements are both better and smaller, but they do not mount the same way.
One area of concern is that the negatve side of that capacitor, and the negative of the power supply, (ground) is tied directly to one side of the AC mains. so caution is needed in dealing with this circuit. There does exist a hazard.
 
Would you like to share the schematic please and the component side where the tubes are. does this look like your unit? :)
Vintage 1940s Televox JUNIOR JUKE BOX 78 RPM Child ' S RECORD PLAYER. Phonograph.

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Wow! A real classic. And with the steel need;es that it will use don't play any vinyl records, it will wear them out first pass. If the cartridge is still good it will deliver at least 2 volts on the loud parts, which is what you need to drive a 50L6 output tube. You might do better selling it to a collector, it is an antique. Totally restoreable, BUT??
REally, the only critical part is the series resistor in the filament string. (R= 35V/ 0.150A, Wattage = 35V x 0.15A, use5 watts) . 20% variation on the other parts will not cause any problems. Aside from the volume control there are the cathode resistor and bypass capacitor, 10 or more MFD, 25 volts min, the screen resistor 2.7K ohms, and possibly a resistor between the two sections of the filter capacitor 2.7K 1W.
 
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