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Silvertone record player/radio modification

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Post by Cbmorgan91 Sun Aug 15, 2021 8:09 am

Hello all,  
 Close to a year ago I bought this radio and have had nothing but trouble getting it going.   As it turns out, one of the transformers is bad.  So on to plan B..
I would like to take the existing chassis and use only what I need to get the record player going.  Also, I've been dabbling a little bit in home recordings, so I think it would be a neat idea for it to have the ability to plug into my computers headphone jack and listen to my home recordings through the original unit. I'm still very new to electronics like this, so I was hoping someone on here can help me with the schematic part.  Like I said, I would like to use the original chassis and whatever tubes necessary to amplify the record player.. I'm attaching the original schematic so feel free to edit whatever needs to be edited to get this project working right. I appreciate all of the help in advance.Silvertone record player/radio modification Screen11

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Post by mr_ed01 Wed Aug 18, 2021 11:14 am

Easiest thing to do is to switch the Silvertone to the phono position and use as is. B+ is removed from the 12BA6 & 12BE6 in the phono position. An isolation transformer would be required when Connecting a AC/DC type radio chassis to a computer.

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Post by Cbmorgan91 Wed Aug 18, 2021 4:40 pm

Thank you very much. I'm going to try to get this thing going in the next couple of days. The coaxial cable that goes from the radio to the phonograph was cut. I made the necessary repairs to that and now I have another question. I do plan on replacing the selenium rectifier with a diode and a resistor of the appropriate size. I desoldered the rectifier several months back and don't remember which side goes where. The rectifier is marked with a positive and a negative on the body. Can you please tell me using the diagram, which wire would be the Plus side?

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Post by mr_ed01 Wed Aug 18, 2021 4:52 pm

Positive end goes to the 33 ohm resistor.  Those small selenium rectifiers don't go bad all that often, play it like it is for a while.

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Post by AJ2X Mon Sep 13, 2021 11:45 am

If you're unfamiliar with modern silicon diodes, the end with the band around it is the positive (+) end -- matching the bar in the schematic symbol. Some selenium rectifiers did mark + and - on the component body. Getting the polarity wrong will possibly cause the electrolytics to fail, perhaps explosively, though the 33 ohm resistor might burn up first.

As someone else noted, be sure you use an isolation (1:1) transformer in the AC line before you connect this radio to an external AC-powered audio source or test equipment. A 100VA size should be more than adequate for this chassis.


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