Laney NEXUS-TUBE - Manual (Page 18)

Laney
OPERATING INSTRUCTIONS
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Care and replacement of Tubes:
Tube amplifiers generally sound much warmer/sweeter than solid state transistor amplifiers but they also need a little more respect due to the fragile
glass tubes themselves. The NXT uses top quality Tubes, two ECC83 preamp tubes, a 12AX7 Phase Splitter Tube and a 12BH7 Tube to drive the
matched set of eight KT88 Output Tubes which should give you years of trouble free service, however like all tube amps; it is important to treat it with
a certain amount of care.Take care when moving the amplifier.
Tubes are fragile glass components; they can easily be damaged if thrown in and out of vehicles.
Allow the amplifier to warm up to room temperature before switching it on. The sudden thermal shock generated can crack the cold glass tube
housing plus any moisture is bad news around high voltage electronics.
Allow the amplifier to cool down after playing before moving. Hot tubes are more susceptible to damage than cool ones.
A tubes life expectancy is based upon a number of factors which include operating temperature, how hard and how often it is played, vibration due to
travel etc. Tubes should be changed in your amplifier if you notice any change in your amplifiers performance etc. They need not be changed at any
regular interval.
Typical problems with preamp tubes can be; a crackley noise, hiss, hum and microphony.
Typical output tube problems can be sound lacking in punch, sound lacks extreme highs or lows and low level hum. The Output tubes can be
replaced singularly if you replace them with the exact same type AND grade as factory fitted otherwise they should be replaced as a matched
set. Exact replacement preamp tubes and matched sets of output tubes are available from Laney via your dealer.
To change a tube:
Switch off the unit and unplug from the mains supply. Wait for the tubes to cool down. Access to the tubes on the rear chassis can be gained by the
removal of the rear grill (8), by unscrewing the four 15mm screws (7) securing it in place. Unclip the spring retainers from the Phase Splitter and
Drive tubes, they can then be gently pulled out from their sockets. Take care when pushing in the new tube to make sure that the pins are all aligned.
The output tubes have a spring retainer fitted the tube socket which grips the base of the tube. The tube must be released from this by pushing the
retaining clips down with one hand, whilst gently rocking and pulling the tube from its socket with the other. Some of the outer row of tubes may need
to be removed to gain access to the tubes on the inner row. Take care when pushing the replacement tube past the retaining clips to ensure that the
rib on the base of the tube is aligned in its locating slot in the socket.
The chassis need to be removed from its wooden sleeve to allow changing of the Pre-Amp tubes, with reference to the diagrams, this is easily
achieved by:
1. Removing the two side handles (5) by unscrewing the six No 8x1" (3) & four M5x30mm (2) on each handle. Remove the metal bar away from
the handle and then gently pull the plastic body out of its recess.
2. Remove the rear grill (8) by unscrewing the four 15mm screws (7) securing it in place.
3. Remove the four M6x30mm bolts (6) and finishing washers (4) from the front of the unit.
4. Finally remove the six M5x30mm screws (2) from the base of the cabinet. You should now be able to slide the amplifier forward freely. Be
careful as the unit is very heavy.
The Pre-Amp tubes can now be removed by unclipping the retaining clips and gently pulling them from their sockets. Take care when fitting the
replacment tubes and ensure that the pins are all aligned properly. Refit the retaining clips.
The chassis is refitted by reversing the removal instructions. Page 18 /24