Harley Benton GA 15 Ultimate Mod Kit Manual page 7

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- Cosmic Ampworks

4. Preparations

Remove the power chord.

2. Unscrew the 8 screws on the back panel of the amp's cabinet and remove the panel.

3. Remove the tubes (2 x 12AX7 preamp tubes and 2 x EL84 power tubes) from underneath the chassis by

carefully pulling and wiggling a bit if necessary. Mark on the bottom of the chassis where the power tubes

(the taller EL84 tubes) and the pre-amp tubes belong, e.g. with a permanent marker. It is all too easy to put

the tubes back in the wrong location afterwards. Make sure the tubes won't roll off your desk; best put

them in a little tray.

4. Unplug the internal speaker from the speaker jack on the back of the chassis and

5. Use a little kitchen knife to lift and remove the brown plastic plugs that cover the screw holes on top of the

cabinet. Remove the screws too, using a suitable Phillips screwdriver; then you should be able to remove

the chassis from the cabinet by slightly lifting and sliding it backwards.

6. Carefully check for any remaining high voltages stored in the filter caps, using a multimeter, as described

above (p. 3 - 5) and keeping the safety warning and advice in mind.

Number all the wires (e.g. 1 - 15) that are attached to the circuit board with spade connectors, by copying

the numbers printed on the board next to each connector on pieces of masking tape. Wrap those around

the correct wires (Figure 6).

Figure 6. Label the wires with little pieces of masking tape before disconnecting the spade connectors, to make sure you put them

back in the correct locations later on. NOTE: I used my own numbering and just wrote those numbers on the circuit board with a

permanent marker.

8. Carefully disconnect all spade connectors, by carefully pulling and wiggling. Pliers may be helpful.

9. Remove the jack retainer bolts from the front of the amp with a small socket spanner.

10. Remove the knobs from the potmeters by loosening the little screw in the back and then pulling them from

the potmeter shaft. Then remove the potmeter washers and unscrew the retaining nuts.

11. Now it should be possible to remove the PCB (printed circuit board) from the chassis.

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- The Ultimate Harley Benton GA15 Mod Kit- Version 1.4 - 200127

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