Octave V70, Manual

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21
10. TROUBLESHOOTING

Hum and crackling
Hum in an audio system is often caused by several system components being earthed individu-
ally. It is particularly common with tuners, VCRs or satellite receivers where the earthed aerial
cables can cause a hum loop via the aerial input.
Tube power amplifiers are normally earthed, and the V 70 is no exception. However, removing
the earth wire on your mains plugs is not a solution, You can isolate the aerial earth connection
with a special signal isolator. This device has no adverse affect on the sound or picture quality
of tuners or TVs.
Check also that the phono plugs are a tight fit. Bend the outer earth contact inwards slightly if
necessary. Sometimes the internal pin in a phono plug may not be a tight enough fit, in which
case you should change either the interconnect cable or the socket.

Switching interference
Older fridges and 12 V halogen lamps can cause cracking through the loudspeakers when they
switch on and off.
Solution : The only solution is to use a single power socket board for your entire system and to
use a different power outlet in your listening room. However, it is not always possible
to eliminate the problem entirely.

Channels are not balanced
1
.
Damaged cables and poorly fitting phono plugs can create resistance in the signal path
enough to reduce the output level of one channel.
Solution : Try new cables or clean the plugs and sockets with isopropyl alcohol.
2. A tape or DAT machine connected to the REC Out may have a faulty Record input (or
faulty interconnect cable) causing the signal to overload. This can result in an imbalance
between the left and right channels.
Solution : Disconnect the tape/DAT machine
3. A faulty output tube can cause a drop in output in one channel and generate distortion at
higher output levels.
Solution : Locate the defective tube using the bias adjustment facility. Replace the
tube.

Increased hiss on one channel
An irregular hissing sound is a sign of a worn driver tube .
Solution : Replace the worn tube.