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• 29 May 2023 - Tube Sockets

  Will • 05/29/2023 at 16:06 • 0 comments

  Tube sockets (also known as valve sockets) come in two main forms: chassis mounting which is where you make a circular hole in a metal chassis and fasten the socket to it, or breadboard mounting where you fasten the tube socket to a wooden breadboard. The majority of tube sockets are chassis mounting because the metal chassis helps screening between circuits. But the breadboard mounted sockets are easier to work with because you don't have to make a large circular hole. Here they are: 

  You can see the 4 pin sockets at the back of the photo, and the 5 and 6 pin sockets at the front. These were difficult to find, and if you're building this project it's perfectly fine to use chassis mounting sockets and spacers, to hold the socket above the breadboard. But I think the breadboard sockets look better.

  The 4-pin sockets are called UX-4, the 5-pin UY-5 and I think the 6-pin is UZ-6. Actually I'm not sure about the last two, you could probably call them UX-4, UX-5 and UX-6.

  In early radio construction you didn't need a soldering iron because the sockets used thumb screws and the circuit could be built by wrapping solid core wire around the thumb screws and nuts and bolts. But I couldn't find any using thumb screws so I will have to use the soldering iron.

• 17 May 2023 - Beauty Parade!

  Will • 05/17/2023 at 21:29 • 0 comments

  I bought most of these a while ago but here they are:

  Presenting from left to right:

  • 1A4P - a pentode with a 4-pin base, the top cap is the control grid.
  • 30 - you can just see the "30" on the glass, this is a low power triode with a 4-pin base.
  • 1F4 - a "power" pentode with a 5-pin base, able to put out 0.5 watt of audio at maximum ratings :)
  • 19 - a double triode with a 6-pin base. This can be used as a class B audio amplifier to deliver a mighty 2 watts of audio!

  Some interesting facts I learned:

  • The earliest vacuum tubes had a two-digit numbering system (30, 19 etc etc).
  • In the 1930's was a "newer" system number letter(s) number where the first number is the heater voltage (approximately), the letters are arbitrary and the last number is the number of electrodes. The 1F4 uses a last number of 4 because it has the filament, control grid, screen grid and anode, and the suppressor grid is internally joined to the filament.
  • All these have 2 volt filaments designed to run from batteries, either a lead-acid cell or a higher voltage fed through a fixed or a variable resistor. When a variable resistor is used, it was called a rheostat and it was adjusted to allow for declining battery voltage during use.
  • The filament is very thin and it runs red-hot (or nearly red-hot) and emits electrons, usually just a few milli-amps. A common mistake when using these valves is applying too much voltage to the filament, which burns them out and makes the valves useless.
  • Any of these could be used as the regenerative detector, or as a low power audio amplifier to drive a pair of headphones.
  • The "power" pentode and the double triode were designed to drive loudspeakers using audio transformers. 
  • Some simple radios used the 19 double triode as a regenerative detector AND an audio amplifier. Thus making an entire radio from one vacuum tube.

  And some terminology:

  • These battery valves are directly heated, meaning current is passed through a fine coated wire causing it to heat up and to emit electrons. This heated wire is the cathode and is also called a filament (USA) or a heater (UK/AUS).
  • Vacuum tubes (USA) or radio valves (UK/AUS) are different names for the same thing. Sometimes I use one and sometimes the other.
  • Valves have an anode which is positive, similar to the collector of an NPN transistor. The anode (UK/AUS) is also called the plate (USA) and collects the electrons emitted by the cathode. 

• 15 May 2023 - Low Voltage Batteries

  Will • 05/15/2023 at 21:17 • 0 comments

  Every project starts with a single step and I have been thinking about this project for a while. The vacuum tubes / radio valves in this project have 2 volt filaments, although alternate tubes/valves can be used that have 1.5 volt filaments. The 2 volt valves were "early" valves designed for lead-acid accumulators and the 1.5 volt were "later" valves invented around the 1940s for dry batteries. So I decided to order two "old-style" 1.5 volt batteries to cover both scenarios - if I use the 2 volt valves I will put the batteries in series and use a resistor to drop the voltage to 2 volts.

  I think these are called No.6 batteries because they are 6 inches tall:

  You can read more about them here: http://prc68.com/I/No6.shtml

  They are also used in electric clocks and I bought these from https://www.kensclockclinic.com/our-no-6-batteries/

  It's perfectly OK to use 1.5 volt D cells and buying these No.6 batteries was a bit extravagant. But they look suitably retro! 

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