RCA Portable TT Convert to Powered Speaker.

[Markmayne]

I'm looking to convert this turntable into a portable tube powered speaker. I want to use the existing speakers and plan 2 add a Bluetooth module where the input molex plug is. My concern is more of the on off switch which would go where the phono motor molex plug is. I have heard of the turntable motor controlling the amount of voltage and I'm afraid of creating an issue. I was wondering if there was any recommendation on wiring and on off switch. Look forward to any input or suggestions. I attached the schematic for reference. I am replacing all resistors, capacitors, the power cord, and adding a fuse.
I also want to note that I understand this is a low wattage amp. I am doing this project as a surprise gift for a friend that gave me this TT because she was going to throw it away as she is not into vinyl the exterior was in bad shape and when she plugged it in there was a bad hum. This unit was her great grandmothers and she is a 20 something year old that wouldn't have a use for it. She said it reminds her of her grandmother so I thought this conversion would repurpose this unit and give it a second life and maybe something she would enjoy. A cool surprise.

 

[maxhifi]

1. The power switch connects pins 1 and 3 of the motor power connector together - the motor is totally independent of the amplifier in this design, you're good to go with it removed. Some phonographs use it to drop voltage to the filament of a power tube - this isn't one of those designs.

2. Be aware this is a "hot chassis" design, which shouldn't be an issue with a bluetooth module, but just take the usual precautions and don't let anything metal be accessible from the exterior.

 

[gadget73]

so the good news is that the motor isn't part of the heater supply. This is just straight across the line, two 50v tubes, a 12v, and a resistor to make up the difference.

To power it, connect pin 1 to pin 3 on the round plug.

The tricky thing here, its hot chassis. One side of the 120v mains ties to chassis ground. You can run a BT module into the original turntable inputs, but only if no parts of it are exposed to the outside world. Powering the BT module may also be interesting. This is going to be a slightly weird suggestion but I think it will work OK.

Figure out what the module needs for current and voltage. I'm guessing its 5v. If it will take a range of inputs, so much the better. Power it from the cathode circuit of the output tubes. You may need to bump the 82 ohm resistor to say 100 ohms to account for the current load of the BT module but thats the only easy clean source of DC that will be available in here, and not cause you grief with the hot chassis thing.

 

[Markmayne]

1. The power switch connects pins 1 and 3 of the motor power connector together - the motor is totally independent of the amplifier in this design, you're good to go with it removed. Some phonographs use it to drop voltage to the filament of a power tube - this isn't one of those designs.

2. Be aware this is a "hot chassis" design, which shouldn't be an issue with a bluetooth module, but just take the usual precautions and don't let anything metal be accessible from the exterior.

Thank you

 

[Markmayne]

so the good news is that the motor isn't part of the heater supply. This is just straight across the line, two 50v tubes, a 12v, and a resistor to make up the difference.

To power it, connect pin 1 to pin 3 on the round plug.

The tricky thing here, its hot chassis. One side of the 120v mains ties to chassis ground. You can run a BT module into the original turntable inputs, but only if no parts of it are exposed to the outside world. Powering the BT module may also be interesting. This is going to be a slightly weird suggestion but I think it will work OK.

Figure out what the module needs for current and voltage. I'm guessing its 5v. If it will take a range of inputs, so much the better. Power it from the cathode circuit of the output tubes. You may need to bump the 82 ohm resistor to say 100 ohms to account for the current load of the BT module but thats the only easy clean source of DC that will be available in here, and not cause you grief with the hot chassis thing.

That makes sense about the Bluetooth. Thank you