Koch Ventura Bedienungsanleitung Seite 4

VENTURA BACK PANEL
[1] POWER: Turns AC power On (red LAMP [10] on)
and Off. When the switch is Off the amplifier is
completely shut down.
[2] A.C. POWER:
INPUT: Power cord input. The VENTURA is equipped
with a worldwide power supply. Inside the amp a mains
selector switch can be set on one of three voltages,
100, 115 or 230. Either of these voltages will work
worldwide with minor power differences. The amp will
work on either 50 or 60 hertz. After resetting the
internal mains selector switch make sure fuses are
replaced with printed ratings on rear of amp.
FUSE: Both fuse and spare fuse are located on the
sled of the fuse holder. Fuse sled can be removed with
a screwdriver. If the fuse should fail, it must be
replaced with the same type and value in order to
avoid damage to the amp and to prevent voiding
the warranty.
If the amp repeatedly blows fuses the amp should be
taken to a qualified service centre for repair.
WARNING: Only a qualified technician should
attempt an input voltage change. Personal injury or
equipment damage may occur if done incorrectly.
WARNING: The fuse should be replaced or the
voltage should be reset only when the power cord
has been disconnected from its power source.
[3] HT FUSE: This fuse protects the power supply in
case of tube failure. If it blows, check for a bad power
tube. If tube-failure is not the cause, the amp should be
taken to a qualified service centre for repair.
This fuse must be replaced with the same type and
value in order to avoid damage to the amp and to
prevent voiding the warranty.
[4] SPEAKER ON/OFF SWITCH: This switch
disconnects the output of the amp from the internal
speaker and connects it to an internal dummy load.
This allows you to play the amp at full power without
hearing anything while using the Recording output [5]
for recording or other purposes.
[5] Rec/PA: This jack provides an unbalanced mono
output suitable for recording or PA. Its signal is derived
from the speaker output so the typical tube saturation
of the power amp will be included; it also includes
Reverb and External Effects signals. This signal is at
line level (-10 to 0 dBV) and is shaped by a special filter
that emulates the typical recording characteristic of a
microphone placed in front of a guitar speaker.
[6] FOOTSWITCH JACK: Provides an input for the
KOCH FS2 FOOTPEDAL or for a remote channel
switching unit, e.g. a MIDI switcher. When the FS2 or
the remote unit is plugged in, the CHANNELS switch
[2] is automatically disconnected.
This jack is a stereo jack.
The TIP connects with the left-hand button of the FS2
footpedal and controls switching between the CLEAN
and the OVERDRIVE channel.
The RING connects with the right-hand button of the
FS2 footpedal and switches the REVERB On and Off.
REPLACING TUBES

SAFETY FIRST: DISCONNECT THE POWER
CORD FROM ITS POWER SOURCE AND LET
HOT TUBES COOL.

CHECK THE 'TUBE LOCATION DIAGRAM' ON
THE CHASSIS FOR THE CORRECT TYPE
NUMBERS AND LOCATIONS.

REPLACE TUBES ONLY WITH ORIGINAL KOCH
HIGH QUALITY TUBES. (IF OTHER TUBES ARE
USED THE WARRANTEE OBLIGATION
EXPIRES)
NOTE: The VENTURA has an auto-bias circuit so it
does not have to be re-biased after replacing the
6V6 power tubes.
If you have any doubts, please take no risks and
let a qualified technician do the job.
Preamp and Power tubes wear out and have to be
changed from time to time to maintain the amps best
performance. Tubes behave like strings, they lose
highs, lows and dynamics and after a period of time
they have to be changed. Exactly when is hard to say
but this is an indication: if you play almost every day
change tubes each year, if you play once or twice a
week change tubes every 2-3 years.
Tubes rarely fail. If they are bad, these might be
the symptoms:
PREAMP TUBES (ECC83, 12AX7, 7025):
- Microphonic whistling or squealing on one or
both channels.
- No or low amp volume on one or both
channels. - Excessive noise on one or both
channels.
POWER TUBES (6V6):
- Loud crackling that is not affected by front panel
controls. - Intermittent or regular blowing fuses.
- Weird amp 'distorting'.
- Hum.
Changing a tube is a simple and quick fix for
most problems in your amp.
In case of failure, just one or both POWER TUBES can
be replaced without re-biasing.
Please always use two matched 6V6 (= one
duet) replacement tubes to obtain the amps
best performance.
Again, if you have any doubts, please take no risks
and consult your dealer and/or a qualified
technician.