Version 1.32
8
solder terminals on the output transformers (8 terminals) should point towards the
front of the amplifier.
Fit the mains transformer using the separate fixing kit supplied. Use the pad either
side, and the large metal disc on the top secured with the long M8 bolt and nut. It is
important to mount the mains transformer so that the wires point towards the front of
the amplifier to avoid inducing mains hum into the output transformers; leave a little
play in the length of its wires. Note: do
not
over-tighten the transformer as this may
crush the windings and destroy it – you have been warned!
If you are building the plus kit the new power transformers that we use are slightly
larger than before and will need to be mounted offset. with either one or two new
holes drilled to take the transformers. Below is a picture of a customers build who
moved the output transformers over slightly so the mains transformers would fit.
However, the offset positioning works just the same.
Finally, fit the complete power supply board using the three M3 stand-offs and M3
screws. There are three positions the board could go in, the easiest for wiring being
the middle position. The capacitors should be at the rear as shown in the picture
above.
Connect the loudspeaker terminals to the output transformers. The black speaker
terminal goes to B1 as well as ground; leave the transformer terminal B1 unsoldered
as the ground wire will be added later. The red terminals go the transformer
connections B3 and B4 (4 or 8 Ohms). Run these wires directly to the output
transformers. B1 is ground tap, (signal ground/earth and chassis ground/earth) B2 is
does not exist any more, B3 is the 4 ohm tap and B4 is the 8 ohm tap. (signal
ground/earth and chassis ground/earth)
After scratching off the paint surrounding the spare hole beside the power supply
fixings, secure the solder tag with an M3 screw and nut. Connect a wire from this tag
to the earth pin (marked E) on the mains input socket to become the earth tag. Wrap a
wire from the earth tag to pin X17 on the power supply board, but leave the earth tag
unsoldered as there are earth wires to be added later. Connect points 1 and 4 on the
mains switch to the remaining pins on the mains inlet socket, as shown in figure 1
below:
