Rivera KNUCKLE HEAD 2 Průvodce řešením problémů stáhnout pdf (Strana 21)

Knuckle

Head

PRESENCE

POWER STANDBY

FOCUS MASTER 2 BASS MIDDLE TREBLE GAIN 2 MASTER 1 TREBLE MIDDLE BASS GAIN 1

BOOST SWEET SCOOP BOOST SELECTNINJA NOTCH BRIGHT

INPUTS

LOW

GAIN

HIGH

GAIN

HANDCRAFTED BY

RIVERA RESEARCH & DEVELOPMENT SYLMAR, CA USA

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CLEAN/RHYTHM LEAD/CRUNCH

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Preamp tube first aid

If you hear ringing (a feedback-like high-pitched sound) in your amp,

it’s probably coming from a preamp tube. Here’s a procedure to find

which tube is giving you trouble.

With nothing plugged into either the High Gain or Low Gain

inputs, and the Master controls turned down to 5 or below, turn the

amp on.

Turn up the Gain on both channels. Now use the tip of a pencil to

gently tap the end of each of the small tubes (V1 through V5) and

listen for sustained ringing. Turn up the Gain and Master knobs and

keep tapping until you find the tube that rings (or squeals).

Turn off the amp, and allow the tubes to cool. Now pull out the

troublesome tube and replace it with one of the same value (that is, if

you’re pulling out a 12AX7, replace it with a 12AX7).

Make sure that the tube is oriented correctly when pulling it out or putting it back in. If you look at the end

of the tube and the socket, you’ll notice that the nine pins are arranged in an incomplete circle. Always make

sure the pins are aligned correctly. Never force a tube into its socket.

Remember to put the sleeve back on after you check or replace a tube.

Power amp tube first aid

Like preamp tubes, power amp tubes can go bad or wear out. Your

KnuckleHead II has four power amp tubes, and if one goes bad, they should

all be replaced. This assures optimum output and tone.

If a power tube shorts out, the HT Fuse will be blown. Remove power from

the amp and replace the fuse before doing the following:

1. Remove the power tubes. Remember the way the eight pins are arranged,

and note that the center hole on the socket has a keyway that matches the

center post on the tube.

2. Replace one tube. Turn the amp on. If the fuse blows (or the tube glows

cherry red, indicating an internal short), you’ve found the bad tube. Turn off

the amp immediately. If the fuse doesn’t blow, replace another tube and turn

the amp on again. Repeat this procedure until you’ve determined which tube

is bad.

3. When the tubes have cooled, remove them. Replace all four tubes. (Don’t throw away the good tubes from

the old set, though—save them as spares!)

Testing a preamp tube: Tap gen-

tly and listen for ringing.

Grip the tube firmly and then

wiggle it out of its socket.

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