The board.

As usual, we’ll start by installing the low-lying components first; The resistors. (1) 100R for the earth-loop breaker section, (4) 47R snubber resistors, and (2) 5K6 drain resistors. The drain resistors get pretty hot, so they should be elevated above the board.

Install the poly capacitors: (2) 100nF bypass caps, (1) 100nF bridge snubber, (4) 47nF diode snubbers, and (1) 1uF high-frequency bypass cap in the earth-loop breaker section.

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.

Install the diode clamp for the earth-loop-breaker.

Install 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.

Install a 14ga jumper wire from points J1A to J1B. Form a piece of wire as shown. Brighten up the ends with steel wool.

Solder the jumper in place.

Mount the diodes to the heatsinks:

The heatsinks are grounded, so the diodes must be electrically insulated from them.

Your kit is supplied with power diodes that are either metal-backed, or plastic-backed and fully-isolated, depending on what’s available at the time. These diodes are a fast-moving sector of the electronics market, with short product life cycles, so the diodes that come with the kit are going to change over time.

With either type of diode, the thermal pad is needed for heat transfer, so there is no difference in mounting procedure.

Stick thermal insulator pads to the heatsinks. Position with a tweezers and push down.

Install a nylon shoulder washer on all four 10mm hex bolts and attach the diodes to the heatsinks with the nylon-insert locknuts. It’s a little tricky to get the diode centered squarely, as it wants to twist as you tighten the nut. Don’t let the diode twist against the thermal pad, or it may tear through, perforate and short to the heatsink. I mount the heatsink in a vise, and then hold the hex-key stationary as I tighten the nut from the other side. Fasten gently! It doesn’t take much torque for the thermal pad to seat fully. The nylon-insert locknut will not allow it to loosen over time. Over-tightening can warp the metal backing of the diode and possibly crack the silicon die.

Check for non-continuity: (Not applicable to plastic-package fully-isolated diodes.)

The heatsinks are connected to the ground plane on the board, so it’s vital that the diodes are not shorted to the heatsinks. Put your meter on continuity check (beeeep!) and verify there is no continuity between the diode body and the heatsink.

Solder the heatsinks to the board, and then solder the diode leads. You’ll need a heavy-duty soldering iron tip to get the solder to flow nicely.

That’s everything installed!

Cleaning: I use an ultrasonic cleaner, filled with 200-proof denatured alcohol. (You can find small ultrasonic cleaners for cheap at Harbor Freight, or at thrift stores. The alcohol is available online, google 200 proof denatured alcohol)


First, check your capacitor polarity!

The giant power supply capacitors in your GFA-565 are a serious explosion hazard if they are connected backwards! As OEM, they are almost certainly oriented the right way, but please check their polarity anyways. The big (+) and (-) markings on the capacitors should agree with the markings on the board.

Aligning the capacitors: The capacitor’s mounting positions will need to be adjusted a little so the terminals line up well with the board. Loosen the (6) M3 nuts that hold the capacitor clamps to the chassis. Fit the BFA-565 board to the tops of the capacitors and install the four terminal screws so that the capacitors are as square as possible. Tighten the as many of the M3 nuts as you can reach, then remove the board again and tighten the rest.

Chassis connections: Two holes are drilled in the chassis, one for the safety earth-ground, and one that connects between amp chassis to amplifier ground, through the earth-loop breaker. The safety earth connection should always have its own, dedicated bolt! (In any device.) I recommend an M5 bolt with lock-washers on both sides. I’m using old capacitor screws. Scrape the paint away around the hole. 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 amplifier 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. The zip tie keeps it from vibrating, and it keeps the resistor–which could get hot in a fault conditon–away from anything flammable.

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-. You’ll notice that you end up with two orange wires and two red wires twisted together, with no way to identify which is which. I use a permanent marker to mark one of the wires at both ends. Alternately, one could install new 22ga wires of a different color.

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. Make sure the capacitor terminal screws are tight. 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.