Power Switch; Line Voltage - Bob Carver CHERRY 180 User Manual

POWER SWITCH

Up is on, down is off. There is no power-on indicator except for the glow of the tubes; you will have to
remember whether you turned it on until you can see the tubes glow. It is safe to switch the amplifier
on and off at will.

LINE VOLTAGE

This amplifier is configured for operation with 120V 60 Hz.
COOLING
Convection cooling - Cool air is drawn from under the chassis by the heat from the tubes acting as an
air pump, and exhausting the warm air out the chassis through the top vents. Do not place the
amplifier on a carpet or in a closed cabinet. You must allow the feet to do their job by keeping the
bottom raised, allowing unimpeded airflow.
MONITORING
Once the bias has been set, it will normally not need to be adjusted for several years unless you want
to experiment for different sound. Or if you install replacement output tubes, or the amplifier
suddenly starts to sound funny. If you hear a POP and see a flash, yet the amp continues to play, you
should first check the current by looking at the front panel meter, and then the 1.5A output tube fuse.
Remember that if either of the fuses blow, the output current will drop to zero. If the TUBE fuse
blows, replace it WITHOUT replacing any tubes. Turn the amp on and monitor the current. If it climbs
to within the range you had set, and if the amp sounds good, all is well.
Often an output tube has a spec of dust-like impurity, which comes into contact with an internal
element, shorts the element and gets itself vaporized into gaseous oblivion. The getter, the mirror-like
shiny plating on the inside of the tube does its job, absorbs the vaporized material and the tube is like
new again. All it takes is a new fuse.
If you install a new fuse and it blows again, you will need to determine which tube is the culprit.
Proceed as follows: turn the amplifier off and allow hot tubes to cool, remove all 6 of the output tubes
and turn the volume control all the way down (full counter clockwise). Turn the amp on and LEAVE IT
ON. While monitoring the bias current by watching the meter, put a tube into socket number six (the
far right front socket). Allow 60 seconds for the tube to warm up. If the bias current comes up to
about one sixth the normal amount, the tube is good. Remove the tube - you can do it with your bare
fingers, as one minute is not long enough for it to get too hot to hold - and install another tube, also in
socket six. Replace one-by-one, until a fuse blows or one of the tubes does not show a bias current.
Replacement tubes are available for free from the Bob Carver factory if one blows under the one year
tube warranty period. If a tube blows beyond the warranty period we recommend you purchase a
replacement from us as we purchase large amounts of tubes and provide a very competitive price for
a tested, known good tube from our preferred tube supplier.
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