The knob of the TU-8300 contains a hole

   inthe inner side in which enables the

   installation of a LED to emit a light on the

   face of the volume knob

    Connecting and soldering
  

   LEDs must be connected in the correct 

   way, the diagram may be labeled “a” or “+”

   for anode and “k” or “-“ for cathode (yes,

   it really is “k”, not “c”, for cathode!).

   The cathode is the shorter lead and which

   may contain a slight flat on the body of

   round LEDs. If you look inside the LED, the

   cathode is the larger electrode (However,

   this is not an official identification method).
  

   LEDs can be damaged by heat when

   soldering, but the risk is minimized if you

   are careful and slow. No special

   precautions are needed for soldering most

   LEDs.

   Solder as finely as possible to the A-node

   of the LED. Cover the A-node lead with  

   tube so that there is no short circuit.
   A ( anode) K (cathode)

  Insert a (M2 × 5) or (M2.3 × 5) screw into

  the small hole located in the back of the

  knob and insert the LED into the hole next 

  to the screw. Next, tighten the screw so

  the lead is wound around the cathode of

  the LED. Finally use a nipper and cut the 

  excess lead. See the picture below for 

  details.

   Make 2 to 3 loops around the inside of the 

   volume knob as shown in the below

   picture.

 

  Carefully attach the knob to the volume 

  axis and ensuring the axis fits in between

  all the wiring.

 

  Appropriate a suitable length of wiring and

  solder it to the nearest “8.5V” pin (1kΩ

  was used here) (as indicated by a yellow

  arrow in the below picture). The two holes

  as indicated by the light green coloured

  arrows are for the illumination of the 

  vacuum tube 12AT7 (see picture 9). A φ3

  sized LED is appropriate to be installed here.

  The tube brightness hole for 12AT7

  (indicated by the red arrow) is where I

  have installed the φ3 sized LED. Both ends

  of the wire are soldered as shown in the

  picture below. Solder the one end of the

  wire connected to the 8.5V as shown in

  picture 7. The cathode is connected to

  the grounding pin as shown below

  The emitting light from the volume knob

  adds to the overall appearance. (the right

  side of 12AT7 with LED light)