PRS Guitars DGT 15 User Manual

Service Notes
Service should only be made by a qualified technician.
Tubes
Tubes are consumables, as they have a given usable lifespan. They are part of the heart of
the tone, so keeping correctly operating tubes is essential. Tubes can fail catastrophically
or gradually, and it's good to know what to look for if they start to go bad. Periodically
inspect them and look to see if anything inside the tube is glowing cherry red other than
the normal orange glow of the filament. This would indicate a situation where the tube
is conducting more current than it is capable of handling and most likely about to fail.
Two other conditions to observe are: 1) filaments not glowing or 2) a miniature fireworks
display inside the tube. Any of the above conditions indicate serious problems with the
DGT 15
tube and should be taken care of immediately. Tubes quite often are the cause of spurious
noise in the amp. Microphonic tubes will squeal or rattle with the vibrations induced by the
speaker cabinet. If suspected, tap each tube lightly with a pencil with the amp powered
USER'S MANUAL
up—the suspect tube will many times let you know. Note that there is a normal metallic
clinking when doing this, but a microphonic tube will be obviously louder.
Replacing DGT 15 tubes will not require any adjustments as both preamp and power
tubes are self-biasing. It is important to refer to the tube chart below and replace any
tubes with the specified tube for that location. After any power tube replacement, initially
inspect them to assure there are no "cherry red" components within the tube. Bias jacks
are provided to help check that the power tubes are working properly. Set your meter to
milliVolts to monitor the power tubes, with +/- 35 mV being the correct approximate value
depending on your tube characteristics.
NOTE! Never power up the amplifier without power tubes installed, as voltages can
rise to levels that may damage internal components.
NOTE! Capacitors may retain an electric charge and can be dangerous even when the
unit is off, unplugged, and has not been played for an extended period of time. USE
CAUTION!!!!
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Product Number: LIT-MAN-DGT 15 Rev. B