INSTALLING EQUALIZER JACK IN THE AC-300

Serial Numbers ___1753 and below

INSTALLING AN EQUALIZER JACK IN YOUR AMPLIFIER COULD REDUCE THE RESALE VALUE OF YOUR UNIT. HILTON AUDIO PRODUCTS WILL NOT ACCEPT FOR TRADE-IN A UNIT THAT HAS BEEN SO MODIFIED.

Equalizer jacks may be installed for either or both the phono or microphone channel. When installing in the microphone channel, microphone 1 must be used. Other than mounting the jack or jacks the wiring is very simple. The jack should be located near the volume control to keep the wire length as short as possible reducing the chance of hum pickup.

Remove the unit from the case as follows: Remove the handle by sliding a screwdriver under the chrome cover and pry it off, exposing the two screws that hold the handle on. Remove these two screws. On the opposite side of the case remove the two rubber feet, held in place by screws. The entire unit will now slide out of the carrying case.

In order to mount the jack it will be necessary to drill a large hole (approx. 1/2" diam.) in the outer chassis, and a 3/8" jack mounting hole in the preamp sub-chassis. These holes must line up with each other. (drilling a small locator hole through both chasis panels, before disassembling, will help line them up).

Stand the unit up so that you have access to the underneath side. Remove the bottom heat plate.

In order to mount the EQ jack it will be necessary to remove the preamp. Remove all the knobs from the controls on the front panel. Remove the small grounding springs underneath knobs if any. Remove the hex nuts from each of the control shafts and mic. jacks.

Remove the plug-in connector at the end of the preamp board. (It will be necessary to loosen the spot of clear plastic that holds it in place). The entire preamp assembly will come out. Now drill the holes in the chassis and sub-chassis for mounting the EQ jack.

Place a small jumper wire on the EQ jack from the (X) terminal to the ring terminal. See drawing 1.

To install phono EQ jack: Locate the printed circuit trace and points A and B using drawing 2 below. With a sharp Exacto knife cut the trace between A & B. Run a wire from A to the tip terminal of the EQ jack and a wire from B to the ring terminal of the EQ jack. Run a wire from the EQ jack ground terminal to the ground trace on the p.c. board.

To install a mic. EQ jack. Locate the .1 ufd capacitor that goes from point C to D using drawing 3 below. Unsolder the side that goes to D. Run a wire from the free end of the capacitor to the tip terminal of the EQ jack. Run a wire from the ring terminal of the EQ jack to point D. Run a wire from the ground terminal on the EQ jack to the ground trace on the p.c. board.