Start by installing the resistors. The drain resistors should be elevated because they get pretty hot.

Install the poly capacitors: (Photo missing, sorry) two 100nF bypass caps, one 100nF bridge snubber, and four 47nF diode snubbers.

Heatsinks: The heatsinks need to be precisely aligned before installation, so there are no gaps between them, and so the mounting holes for the TO-220 diodes are perfectly aligned. Clamp the heatsinks in a vise, making sure they are square and level as you can get them, and that their backs are flat against each other.

Place the board onto the heatsinks and solder the pins in place.

The second pair of heatsinks require one extra step to install. The first pair of heatsinks will interfere with placing the board down onto the vise. Instead, to hold the heatsinks in place together and aligned, clamp them in the vise, and temporarily install the M3 screw and lock-nut.

Then, solder them to the board and remove the screw.

Perfectly aligned.

Stick a thermal pad to each heatsink. Use a tweezers to line it up with the mounting hole, and press it down.

Install the TO-220 diodes, but don’t solder them in yet. Use the 16mm button-head hex screw with a nylon insulating washer on each side. Tighten them gently. Don’t overdo it. The nylon-insert locknuts will not allow the screws to come loose. Over-tightening can bend the metal tab of the diode, or pinch through the insulator pad. Use a pliers to hold the nut. (Unfortunately a nut-driver won’t fit.) As an extra precaution, use your multimeter’s continuity beeper to verify there is no connection between the diode’s metal mounting tab and the heatsinks. The heatsinks are connected to ground on the PCB.

Solder the diodes.

Terminal blocks: They snap together like Lego! Assemble a row of eight 45-degree terminals and solder them in place.

And the vertical terminals for V+ and V-, and the smaller 45-degree ones that provide power to the input board.

…and the diode clamp for the earth-loop-breaker.

And the electrolytic bypass caps and the fuseholders.

Optionally, if you are keeping the original back-panel fuseholders, instead of using the fuseholders on the board, install a jumper to bypass the on-board fuseholders. You would then wire the power in the same manner as OEM: The output of the power supply board goes to the back-panel fuseholders instead of directly to the output modules.

Bypass if keeping original back-panel fuseholders.

Finally, a jumper is installed from points J1A to J1B. Form a piece of wire like so, and solder it in place.


I clean mine in an ultrasonic cleaner, and I highly recommend that.

The board is attached to the tops of the capacitors, and then the capacitor clamps are tightened.

Two holes are drilled in the chassis, one for the safety earth-ground and one the chassis ground connection that connects amp ground to the chassis through the earth-loop breaker. The safety earth connection should always have its own bolt! (In any device.) I recommend an M5 bolt with lock-washers on both sides. I’m using old capacitor screws. Notice I’ve abandoned the OEM ground hole and drilled these new holes closer to the power supply capacitors, so the wire to the power supply board is as short as possible. These two points should be close together so they don’t pick up currents induced into the chassis by the transformer and the internal wiring. This is the point where safety earth meets amplifier “ground”–the thing the amplifer considers zero–as best we can make it.

A 14ga wire with a ring terminal is run from the chassis to the chassis ground connection on the power supply board.

The safety earth ground is bolted next to the chassis ground.

The DC rail fuseholders are removed from the back panel, hole plugs installed, and a sticker applied.

Incidentally, here’s how I do the binding posts with the zobel and feedback wire attached.

Connect the power wires for the input board; Fused V+, Fused V-, Un-Fused V- and Un-Fused V+. The red wires are for V+ and orange for V-.

Connect the Input board ground, and speaker ground terminals.

Install your output modules if they are not already there, and connect the output module bypass ground wires.

That’s it! Take some time to double-check all your connections before attempting to power-up the amp. If you are using a variac or dim-bulb-tester, be sure to jumper across the 4.7 ohm soft-start resistor.

Some more pictures showing how I do the wire bundling in a GFA-565.