Manley Labs MM/MC GRAMOPHONE CARTRIDGE PREAMPLIFIER owner manual Symptom, Possible Cause

Symptom Possible Cause Corrective Action, cont’d

Lights ON, no output either 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.

Open 6922 filament, either channel. 6922 unplugged.

Output MUTE function activated.

Input connectors are non- shorting.

Ground link between CHAS- SYS and CIRCUIT open.

Turntable / tonearm ground link to CHASSIS open.

Open cartridge leads.

Phono plugs not fully in- serted.

‘Table lines close to hum magnetic field.

Ground loop between STEELHEAD and turntable or downstream pre-amp/ power amplifiers.

Faulty shield connection, input or output interconnect cables.

Check DIN plug wiring Left: 1high, 4 low. Right: 3 high, 5 low, Shield: 2 earth, chassis.

Check for glowing 6922 filaments. Replace if necessary.

UnMUTE the preamp.

Avoid unused inputs; install shorting plugs.

Replace jumper if necessary

Establish inter-chassis connection.

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 elements.

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 amplification 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.

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