Bugera 1990 - Footswitch and Internal Components; Footswitch Channel Activation; Internal Valve Layout; Bias Adjustment and Testing Procedures

7 BUGERA 1990 User Manual
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Footswitch
Footswitch
(27) The CLEAN switch activates the CLEAN channel.
(28) The LEAD switch activates the LEAD channel.
Inside the BUGERA
DANGER!
High voltage! Risk of death!
High voltages of up to 500 V DC may be present inside the casing for
long periods after being disconnected from the mains. To avoid lethal
electric shock, do not open the casing. There are no user-serviceable
components inside. Refer all maintenance to qualied service
personnel. Remove the mains cable when the unit is not in use.
Inside the BUGERA 1990
(27) (28)
(30)(31)(32)
(29)

The parts inside the amplier operate at high voltages and high
temperatures. To avoid damage and injury that results from re or
electric shock, do not drop or spill anything into the unit’scasing.
INSTRUCTIONS FOR QUALIFIED SERVICE
PERSONNELONLY
Remove the backside of the amplier’s casing to get to the valves and the
controlelements.
(29) These are the sockets for the ECC38/ECC38A preamp valves.
(30) These are the sockets for the 5881 power amp valves.

(31) The BIAS TEST connector lets you connect a voltmeter in order to measure
the power amp valves (bias adjustment). Make sure that the voltmeter is set
to direct current (DC).
(32) The BIAS ADJUST control is used to make the bias-adjustment.
◊ Replacing the power amp valves also requires bias adjustment.
You should always use sets of four matched valves. The valves of the
BUGERA Series are ideal for this purpose.
 CAUTION:
WE HIGHLY RECOMMEND THAT BIAS ADJUSTMENTS BE CARRIED OUT BY
QUALIFIED PERSONNEL!