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.
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
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
Parallel push pull with triode connection.
Step 4: Ingredients
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
Step 6: Build Amplifier Circuits
Step 7: Controller
on/off : push tuning dial ( toggle)
FF/REW : turn clockwise/counterclockwise
Step 8: Heat Exhaust System
Unless lithium battery prohibit heat, it would explode! ,So heat exhausting system is absolutely needed.
Make windows and set fan and partition.