Part 3 - Reading your schematic



Click on the picture above to open a window showing the WF-55's full-size schematic. This is the same circuit as the block diagram shown in Part 2, but with all of the component values added and with numbered lugs for all off-board components (see Solder lug numbering, right). All components are numbered on the schematic (R1, C3, D4, etc), so that you can relate this schematic to your Kit contents listing and the turret board layout (Part 5).
      It's the specific values in the circuit that combine to make the amplifier work and sound the way that it does. For example, capacitor C1 does two jobs. The first is to block the high DC voltage (supplied to the first stage of the preamp via resistor R3 and R10) from feeding into the input of the second amplification stage; any value of capacitor would work for this task. The second job that the capacitor does is to control the amount of lower frequencies in the amplified guitar signal that are passed from the first amplification stage to the second - higher values allow more bass through, lower values allow less.


Build now, tweak later

It's the ease with which you can alter individual components in an amp circuit that makes hand-wired amps so appealing. For example, you can swap in components with the same ratings but different values to change the response of part of the circuit. This is the real beauty of building your own amp - you can fine-tune it to the tone you like.
      It's best to get your amp up and running first, by sticking to the components specified on the schematic and supplied with your kit. There are many ways to tweak the vintage 5F1 Champ circuit, and you can decide if you want to try that when the amplifier is working properly as standard. While it may be tempting to leap ahead and increase the bass frequencies by using other capacitor values, for example, doing this in the wrong part of amp circuit may inadvertently cause your amp's distortion tone to become 'muddy'.
Solder lug numbering
Look closely at your schematic and you'll see numbering for the solder lugs of some of the components. For example, the jack sockets, control pot and mains input socket each have 3 solder lugs. To avoid any confusion, your schematic includes numbers next to each connection for these components, and at the bottom left of the schematic there's also an annotated photo reference for each.


      There are nine solder lugs on the underside of the preamp valve socket. These are numbered clockwise, starting at the gap.

      The second and larger valve socket is an 8-pin type (to accept the WF-55's 6V6 power valve). This socket has a small keying 'notch' in the central round hole - which you can just see here at the 3-o'clock position. Look closely and you'll see pin numbers (1 to 8) moulded in the underside next to each solder lug, working clockwise from this keying notch. However, they're almost impossible to see in anything other than the brightest light, so I've added annotations here for easier reference.


  WF-55 construction guide
  1 - Kit contents
  2 - Block diagram
  3 - Reading your schematic
  4 - Chassis assembly
  5 - Turret board assembly
  6 - Turret board wiring
  7 - Chassis wiring guide I
  8 - Chassis wiring guide II
  9 - Chassis wiring guide III
  10 - Initial testing
  11 - Final test

  WF-55 kit purchase page

  WF-55 construction guide
  1 - Kit contents
  2 - Block diagram
  3 - Reading your schematic
  4 - Chassis assembly
  5 - Turret board assembly
  6 - Turret board wiring
  7 - Chassis wiring guide I
  8 - Chassis wiring guide II
  9 - Chassis wiring guide III
  10 - Initial testing
  11 - Final test

  WF-55 kit purchase page