User`s manual

USER’S MANUAL
Electronaut M63 Vacuum Tube Microphone/Instrument Preamplifier
14
E L E C T R O N A U T  C O M P A N Y
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Replacing the fuse
To check and/or replace the fuse, unplug the M63 from the line voltage outlet and remove the power cord from the
IEC power connector. Using a small flathead screwdriver, pluck the fuse drawer out of the IEC connector. Replace
the fuse if necessary with a 240V, 1A 5mm fuse (there’s a spare in the little drawer!) and re-insert the drawer into
the IEC connector. In the unlikely event that the fuse blows twice in a row, a fault should be suspected and the M63
should be given to a qualified technician for service.
Replacing the Pilot Lamp Bulb
Replacement pilot-light bulbs can be obtained from Electronaut. This bulb has a finite life and will occasionally
need to be replaced. It is an 18 volt, 80 mA “bantam” type bulb. DO NOT USE A REPLACEMENT BULB RATED
FOR MORE THAN 80 mA.
To replace the bulb, remove the amber jewel on the front of the faceplate by turning it counterclockwise. Then,
place your thumb and index finger on the top of the bulb and press inward while turning counterclockwise one half
turn. The bulb should release from the socket. Pull it out, then put the replacement bulb in there and press while
turning clockwise one half turn. The bulb should lock into the lamp socket. Replace the amber jewel.
Replacing the VU Meter Bulbs
The VU meter bulbs have a finite life and will occassionally need to be replaced. To replace the VU meter bulbs,
follow the procedure below:
1) Turn off the M63, unplug the AC mains cable, and wait about five minutes.
2) Remove the top cover and set it aside.
3) Pluck out the burned out bulb from the meter, and replace it with a new one.
4) Put the cover back on. Do not tighten the top cover screws with a screwdriver until all the screws have been
inserted and lightly tightened by hand. Do not over-tighten the screws.
NOTE: The VU meter bulbs are 12 volt, 1.5 watt “Festoon” type bulbs. Replacement bulbs are available from
Electronaut. DO NOT USE A BULB RATED FOR MORE THAN 1.5 WATTS, OR 125 mA!
A note about powering down the M63 when the PAD is on
The heavy-duty toggle switches on the front panel of the M63 do not actually carry any audio. Instead, the
switches are used as remote controls for several high-quality, sealed relays with gold plated contacts that are
mounted on the ampliers’ circuit boards. This avoids routing the audio up to the front panel and back several
times, reduces the length of the signal path and associated stray capacitances, and reduces noise. It should be
noted, however, that because these relays require a small amount of power to remain in position, they will reset
themselves to their default, unenergized positions when the power to the M63 is turned off. If you are putting a
HOT signal into the M63 and have the -20 dB PAD engaged, then suddenly turn off the power to the M63, the
PAD will become disengaged and you will have 20 dB more level coming out of the preamplifier until the reserve
power drains away from the power supply! Please keep this in mind before randomly switching off the M63 while
in use!