Amp Maker Home | WF-55 purchase page

Home > WF-55 Construction manual > WF-55 Chassis wiring - part 1

WF-55 Chassis wiring - part 1

By now, you should have a chassis with almost everything in place: both transformers, a pair of valve sockets and all front and rear panel controls. You also have a turret board with 11 wires sprouting from underneath it. Put the turret board to one side while you wire up the rest of the components.

Connecting the mains supply

First, use a short piece of green wire to connect the Earth lug of the integrated IEC/fuseholder to the solder lug that's closest to the back panel. Then use some brown and blue wiring to connect the IEC/fuseholder (brown wire for Live, blue for Neutral) to the centre pair of lugs on the On/Off switch (S1). The result will look like the first photo on the right.
      Now take two pieces of red wire and solder them to the upper pair of solder lugs on the On/Off switch. Twist them together and run them along the side of the chassis to the power transformer, T1. Connect - but don't solder - these two red wires to the outer pair of lugs labelled 0V and 120V. Connect another pair of red wires to this same pair of lugs and run them up to the neon indicator on the front panel. Now solder all four solder lugs (two on the transformer and two on the neon indicator).
      Finally, make a short connecting wire and connect the centre pair of lugs (120V and 0V). This completes the wiring for the mains side of the amplifier. The result should look like that shown on the right.

Start by wiring up the combined IEC/fuseholder and On/Off switch

The neon indicator and On/Off switch connect to the power transformer's primary winding. Don't forget the short red connecting wire!

Adding the valve heater wiring

Solder three long lengths of wire (two green and one black) to the three 6.3V - CT - 0 solder lugs on the power transformer: green to the 0 and 6.3 lugs and black to the centre lug (CT). Twist them together. These wires need to be long enough to run to the back of the chassis, along the chassis edge and around to the power valve, V2. Attach the green wires to pins 2 and 7 of V2 (either way round is fine) and the black wire to pin 8.
      Now take two more pieces of green wire and attach them to the same pair of pins as the other green wires (pins 2 and 7 of V2). Twist these wires together and run them along the edge of the chassis to the preamp valve, V1. Strip the ends of these wires; attach one to pin 9 of V1, and attach the other to BOTH pin 4 and pin 5. One way to do this is to strip the insulation to expose around 1cm of the copper wire - this will be long enough to pass through pin 4 and then back through pin 5.
      Now you can solder all of these pins. The pins are quite tightly packed on these 9-pin valve sockets, so be very careful to avoid 'whiskers' from these wires shorting against adjacent pins.

Twist the heater wires to keep them together, but don't worry if the twists aren't tight: it's neither tone- nor noise-critical

When you've completed the wiring of the valve heaters, your chassis should look something like this

Add the power valve's plate wire

You're almost ready to add the turret board, but before you do, there's one more wire that's easier to add now - before the board goes in. Take a 30cm (12-in) length of brown wire and solder it to pin 3 of the V2 socket (the power valve). Run the other end of it over to the rubber grommet in the centre of the chassis and push it through; it will connect to the output transformer (T2) later.

Add the plate-to-output-transformer wire before fitting the turret board

Amp Maker Home | WF-55 purchase page
All text and graphics are copyright of Amp Maker and may not be used without prior agreement.