Symptom
Lights ON, no output from ei-
ther channel after warm-up delay
times out.
Hum heard on unused MM or MC
inputs.
Hum heard on active inputs.
No or bad sound heard on MC2
input.
Possible Cause
Open 6922
fi
lament, either chan-
nel. 6922 unplugged.
Output MUTE function activated.
Input connectors are non-shorting.
Ground link between CHASSIS
and CIRCUIT open.
Turntable/tonearm ground link to
CHASSIS open.
Open cartridge leads.
Phono plugs not fully inserted.
Turntable lines close to hum mag-
netic
fi
eld.
Ground loop between STEEL-
HEAD and turntable or down-
stream preamp/power ampli
fi
ers.
Faulty shield connection, input or
output interconnect cables.
Check DIN plug wiring:
Left: 1 high, 4 low.
Right: 3 high, 5 low.
Shield: 2 earth, chassis.
Corrective Action, con’t
Check for glowing 6922
fi
la-
ments. Replace if necessary.
UnMUTE the preamp.
Avoid unused inputs; install
shorting plugs.
Replace jumper if necessary.
Establish inter-chassis connec-
tion.
Check lead/head-shell continuity.
Check for proper connection.
Keep source lines away from
transformers, motors, etc.
Break ground connection of one
or two of the three system ele-
ments. Experimentation may be
necessary.
Roll or swap cables, or replace
cables.
Re-wire plug for continuity.
Remarks on hum pick-up:
Please be aware that the STEELHEAD can develop voltage ampli
fi
cation
factors as high as 30,000 times, or 90 dB at the 50-60 Hz power line “hum” frequencies. It is of the utmost
importance that cables handling the tiny signals from the phono cartridges be of high quality, with good
screening and connection properties, if the single-ended signal is to have any chance of being received by
the preamp reasonably free from hum and noise intrusions. This is especially true formoving coil pickups.
Please use the shortest practical interconnects and carefully route these away from all possible electrical or
magnetic hum or interference sources.
17
