Koch Powertone III Bedienungsanleitung PDF herunterladen (Seite 5)

[2] A.C. POWER:

INPUT - Power cord input. The amp 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 in the sled of the

fuseholder. 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, check for a bad power tube. If

tube-failure is not the cause, the amp should be taken to a qualified

service center for repair.

WARNING: Only a qualified technician should attempt an input

voltage change. Personel 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 center for

repair.

This fuse also must be replaced with the same type and value

in order to avoid damage to the amp and to prevent voiding

the warranty.

[4] FS-4 FOOTSWITCH CONNECTOR: Provides an input for the

FS-4 footswitch and disconnects the CHANNELS [FP 2], the GAIN

BOOST [FP 6] and the OTS [FP 10] switches, when the footswitch

is plugged in.

FS-4 FOOTSWITCH

The included FS-4 Footswitch is equipped with four switches:

- CHANNEL for selecting channels (Channel-2 = red LED ON).

- BOOST for activating the Gain Boost in Channel-2 (red LED).

- OTS for activating the OTS circuit (yellow LED).

- MASTER for selecting Volume-I [15] or Volume-II [16] (Volume-II

= green LED ON).

[5] These three stereo jacks provide an input for separate remote

control units like the Koch FS-2 footpedal or a MIDI switcher.

Jack-1 tip: Channels 1/2

ring: Ch2 gain Boost

Jack-2 tip: OTS on/off

ring: Master Volume 1/2

Jack-3 tip: FX loop 1 on/bypass

ring: FX loop 2 on/bypass

EFFECT LOOPS 1 & 2

[6,7] SERIAL/PARALLEL - SEND: This jack provides a tube

buffered mono output from the preamp of the POWERTONE-III and

can be used to connect an external effects unit. This jack must be

connected with the input of the effects unit (see also CONNECTION

DIAGRAM page).

[6,7] SERIAL - RETURN: This jack provides an input for an

external effects unit and must be connected to the output of the unit.

When used, it disconnects the preamp of the POWERTONE-III

from the power amp.

[6,7] PARALLEL - RETURN: This jack provides an input for an

external effects unit and must be connected to the output of the unit.

[6,7] LEVEL: Controls the amount of Effects signal mixed with the

original dry signal of the Parallel Effects loop.

If this loop is used, direct signal must be taken off the effects

unit's signal. For example by turning the effects unit's ‘dry/wet’

control to ‘wet’.

NOTE: These effect loops operate on a -10dBV signal level which

guarantees compatibility with both instrument-level effects like

floor-pedals and guitar-processors, as well as line-level effects

like professional 19 inch rack mount devices.

If connecting an effects unit to the POWERTONE-III causes

hum, a ground-loop may be the cause of it.

[8] SPEAKER OUTPUT JACKS: Provided for connection of

speaker(s) or speaker cabinet(s) with an impedance of 1x4/2x8

ohms, OR 1x8/2x16 ohms, OR 1x16 ohms. (see also CONNECTION

DIAGRAM page)

WARNING: Never play the POWERTONE-III without a speaker

connected. This may cause serious damage to either the power

tubes and/or the output transformer.

ALWAYS USE SPEAKER CABLE.

[9] REC/PA OUTPUT: ThIs jack provides a mono output from the

power amp and includes External Effects signals. The signal is

derived from the speaker output and filtered by a special Filter

which emulates the sound coming from the speaker, so it can be

fed directly into a recording or sound reinforcement mixer.

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)

 BEFORE REPLACING THE POWER TUBES, REMOVE THE

CE SAFETY CAP FIRST.

 AFTER REPLACING THE POWER TUBES, PUT THE CE

SAFETY CAP BACK IN PLACE.

NOTE: Always have the amp rebiased after replacing the power

tubes. Biasing instructions can be found inside the amp. Rebiasing

the amp is not neccessary only if Koch power tubes are used with

the same type and bias-class number.

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 POWERTONE-III’s best musical

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 (EL34):

- 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 all POWER TUBES can be replaced

without rebiasing only if KOCH tubes with the SAME TYPE AND

BIAS-CLASS NUMBER are used.

If EL34’s with a different or unknown bias-class number are used

for replacement, ALL POWER TUBES have to be replaced and the

amp has to be REBIASED.

Please always use a set of matched EL34's replacement tubes

to obtain the amp's best performance.

Again, if you have any doubts, please take no risks and consult

your dealer and/or a qualified technician

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