Building the Tube Overdrive

Notes:

  • Almost all component values have changed since the PCB was manufactured. See diagram below for changes.
  • Circuit based on the Mitsumin Valvecaster, specifically the “6111 Sub Caster”. This PCB also has components added for many of the popular modifications. Tons of info here.
  • Power regulator needs a heat-sink. A simple clip-on worked fine, but it still got very hot. The regulator IC is mounted so that it can be bent inwards so the heatsink is pointing down if a larger heatsink is needed.
  • Component values are very tweakable.


BOM:

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Schematic:


Build Instructions:

Clean PCB with isopropyl alcohol to remove any manufacturing residues.

If necessary, separate panels carefully by gently flexing and twisting back and forth, ensuring that they break cleanly at the “mouse bites”. File the leftover tabs down until flush with the edge of the panel or PCB.

 


Solder the surface mount devices.

Solder the through-hole parts, including power lead, but NOT tube (yet). Ensure the regulator is installed properly (metal tab/back facing outwards).

(The power regulator isn’t shown as installed in these pictures.)

Note how the LED is mounted flush to the top of the PCB. The tube is mounted over the LED to glow more brightly. Yellow or orange LEDs give a warm glow. White or blue is “futuristic”. Red or green is creepy (but in a good way).

Check for shorts, then apply power to make sure the LED is working. Also check for 6.3 volts on the middle pin of the power regulator. Because there’s no load it will probably be higher than than, but should be under 9V.


Mount the tube. The pins make a “U” shape with the top of the “U” facing the top of the PCB.

Before soldering the leads, bend them outwards to force them into contact with their pin holes, then apply power. You should see the two filaments at the top of the tube start to glow after 10 seconds. Measure the middle regulator pin — it should be between 6.2 and 6.4 volts. The 220 and 890 ohm resistors next to the regulator control the voltage. If you’re using 1% resistors it should be okay.

The regulator will get very hot so keep the testing under a minute or use a heatsink.

Even if the audio isn’t working, as long as the filament voltage is okay then it’s safe to solder the tube in and trim the leads. Keep enough length for clipping a test lead to.


If no sound, double and triple check component values.

 

TBD: Label component property with ranges for mods.


Mods and Alternative Component Values

There’s a great compilation of information here.

Here’s a key for converting from the Dano schematic. Note that the original component values are based on getting a guitar signal and going to an amplifier. The Tube Overdrive Tile circuit contains extra components where useful.