Single Pole Single Throw (SPST) switches? In other words, do these switches
continuously connect to GND when you wish to activate the given function?
If you're unsure about the answers to these questions, consult an authorized
service center or a professional specialist.
-> Is at least one speaker connected to the speaker outputs 4 ohms, 8 ohms
or 16 ohms (28, 29, 30, 31, 32) ?
-> Is the power amp activated (Standby switch to ON) ?
-> Are all cords (guitar, effect, and speaker) connected properly
and are they functional ?
-> Unplug connected effectors and see if the preamp works fine without
these peripheral devices.
-> Is the Noise Gate activated in one of the Lead channels and the Threshold (24)
knob set to a high value? Deactivate the Noise Gate (24) for a quick check.
-> Are the active Master knob and the Gain and Volume knobs set to a value
greater than 0 ? If any of these knobs is set to 0 (far left position),
no signal is routed to the amp's outputs.
-> You may be looking at a faulty tube or another defect. In this case,
be sure to take the preamp to an authorized, professional service center.
-> Is there a connection (for example, via a shielded circuit) between the
amp and another device that is grounded via a power plug of its own?
Two or more circuits sharing a common electrical ground line can cause
audible hum. If low-frequency noise is emanating from your rig,
be sure to consult a specialist.
-> The amp and mains grounds are not connected properly or are altogether
disconnected. Have an experienced specialist check this.
-> Cords connected to the input or effect loops may not be shielded properly.
Replace them to check if this is indeed the case.
-> The amp or speaker cords may be picking up interference from powerful
magnetic fields (for example, of nearby power transformers or electrical motors).
Reposition the amp and connector cables.
-> The amp or speaker cords may be picking up radio signals, for example,
from activated mobile telephones or powerful local transmitting stations nearby.
Switch off mobile phones while troubleshooting noise problems.
* The amp is not providing an output signal / no sound is emanating
from the speaker.
* The speaker is emitting humming noises:
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