Bluetooth Tube Radio Receiver No.6 "Completely Portable




Introduction: Bluetooth Tube Radio Receiver No.6 "Completely Portable

The sixth project is The Portable Tube Radio.

I once made some battery operated portable amplifiers. But they anyway needs wires to connect sources and speakers, because there was no such way to connect source without wire then. But now we've got Bluetooth, I have realized my long-cherished dream.

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Step 1: The Receiver

RCA Victor 45B is a portable radio receiver.

Before the birth of transistr radio, there were many kind of such battery tub radio.

Battery tube needs 2 Power supply, "A" is for fillament, low (1.5 or 3V) voltae high current and "B" is for tube's anode,High vlotage(45 or 67.5V) low current. Around that time all of portable radios have two batteries in them.

Step 2: Tubes

3B4 is a filament type transmitting tube for battery operated portable devices.

3A5 is a twin triode for high frequency

5676 is subminiatut battery tube for high frequency

These battery tubes are filament cathode type, so Every filament circuit should be isolated.

Step 3: The Circuit

All parts and modules are crammed into such a small space, there is no way but compact and low efficient speakers, So such receiver inevitably needs more power, and output of battery tubes are very small ,so we should employ most powerful circuit without sacrificing audio quality. It is my best answer.
Parallel push pull with triode connection.

Step 4: Ingredients

1.Tube Portable receiver RCA Model 45B2
2.Vacuum tubes
i) 3B4 (miniature battery tube for transmitter) * 4
ii) 3A5 (miniature battery tube :twin triode) *1
iii) 5676 (subminiature battery tube;triode) *1
3.Lithium ion Battery 12V
Nowadays there are small,high efficient and cheap isolatd DC-DC convers. so we can build battery tube device with single battery

4. Isolated DC-DC converters
5..PIC microprocessor 12F675 and a rotary encoder
6.Bluetooth audio module KRC-86B
7.output transformer (Ichikawa
8.12V 2.5cm fan *2
9.capacitors, resisters, universal PCB, etc...

Step 5: Disassembling

Remove Crome plated front panel and disassemble. some parts (sockets, VR, etc.) are re-used. The original receiver's main switch is connected close-and-open action of lid. I preserved this interesting mechanism.

Step 6: Build Amplifier Circuits

Cram amplifier circuit in the vacant space. The first and second stage needs one tube each, and output stage needs four tubes, so we need the place to set 6 tubes , but The sub-chassis for tubes has only four sockets and can be placed another. There is no other place to place one more tube. in such act of desperation, I employed subminiature tube 5676.

Step 7: Controller

KRC-86B Bluetooth module has play/stop FF/REW key function. I assigned these functions to tuning dial with using rotary encoder and PIC 12F675 microprocessor as below.

on/off : push tuning dial ( toggle)
FF/REW : turn clockwise/counterclockwise

Step 8: Heat Exhaust System

Originally the receiver has four tubes, and these tubes and battery are neighboring each other. Now, all of four tubes has become power tube, and manganate battery replaced lithium battery.
Unless lithium battery prohibit heat, it would explode! ,So heat exhausting system is absolutely needed.

Make windows and set fan and partition.

Step 9: Position of Intestinal Organs

Step 10: Finish

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    8 Discussions


    4 years ago

    Nice work!


    4 years ago

    can you supply the scematic for the 100V power supply part

    i am gonna upgrade my portable tube amp and i need a easyer way to get the high voltage (a bunch of 23A battery's aint gonna do it)


    Reply 4 years ago

    I once made a step-up dc-dc converter fro scratch, It consisted of square wave oscillator, audio amplifier and small transformer.
    it had very poor efficiency, so i have never made since then.

    The neatest way is using step-up DC-DC converter. but I cannot find on the web one that can output more than 100V.
    The second best is stack isolated DC-DC converters. such as :

    Stacking four 24V converters, you would get 96V (sorry, I have not tried yet)


    Reply 4 years ago

    I used in this instructables a step-up DC-DC converter IDEC "PSR-BE03 qpp-12". Though it had been discontinued long before,

    there are many kind of step-up DC-DC converters, such as

    High Quality Boost Converter Step-up Module Power Supply 600W DC-DC 10V-60V to 12V-80V NG4S

    The simplest way is using car inverters. you can find them in automobile parts store or online store. Rectify their output you can get 150-300V DC with adequate current.


    Reply 4 years ago

    600W is a lot for a tube amp that only needs a few ma


    4 years ago

    I'm inspired with this one, and you didn't over-explain for the "paint by numbers" crowd. Thanks!


    Reply 4 years ago

    Thank you .

    I cannot find no amusement in the kinds of paint by numbers too, and Different from painting it is sometimes dangerous for beginners. The most dangerous thing is doing something without recognizing himself what he is doing, I think.

    Edward Phantom
    Edward Phantom

    4 years ago

    Hey, i like it! How is going the life inside your vault-tec vault?