Octave RE290 User manual

RE 290

3
INTRODUCTION
Congratulations and thank you for choosing OCTAVE!
RE 290
You are now the owner of one of the world's most innovative and reliable amplifiers. Look
after it, and it will provide you many years of listening pleasure.
You often hear people claim that tube amplifier design has not progressed for years. The
operating principles of tubes have indeed been documented extensively and are well
known to amplifier designers. Of course, the same can be said for transistor amplifiers.
However, advances in both technologies are still possible thanks to the development of
innovative and improved components, our greater appreciation of the fundamental
principles and, of course, deeper and more advanced insights into the interaction of
amplifier and loudspeaker. With tube amplifiers in particular, a general reluctance to
depart from the classic circuit designs has not done the technology any favors. Although
today's loudspeakers and source equipment provide better performance than ever before,
they also present greater demands on amplifiers. Modern sound reproduction equipment
delivers a level of performance at a price that simply would not have been possible 20 or
even 10 years ago.
These advances have been achieved through the application of the latest technological
developments as they become available and affordable. OCTAVE has specialized in tube
amplification for the past 25 years, during which time we have developed a number of
innovative technologies that have earned us a reputation as one of the leaders in the
field.
Here's wishing you many happy hours of musical pleasure!
Andreas Hofmann

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5
CONTENTS
Page
Introduction ................................................................................................. 3
1. Description of the RE 290............................................................................ 7
2. Safety instructions ....................................................................................... 8
2.1 Before you begin.......................................................................................... 8
2.2 Placement .................................................................................................... 9
2.3 Warranty....................................................................................................... 9
3. Getting started.............................................................................................. 10
3.1 Unpacking, package contents...................................................................... 10
3.2 Removing the grille ...................................................................................... 10
3.3 Installing the power tubes ............................................................................ 11
3.4 Switching on for the first time: the soft-start feature .................................... 11
3.5 Checking the tubes (BIAS)........................................................................... 12
3.6 Connecting the unit...................................................................................... 12
4. Front panel controls ..................................................................................... 13
5. Rear panel connections ............................................................................... 14
6. Advanced functions...................................................................................... 16
6.1 Power selector, alternative power tubes...................................................... 16
6.2 Electronic Protection System....................................................................... 17
6.3 Soft-Start, Inrush current limitation .............................................................. 17
6.4 Ecomode (power saving mode)................................................................... 18
7. Tubes ........................................................................................................... 19
7.1 Removing the grille ...................................................................................... 19
7.2 Tube layout .................................................................................................. 19
7.3 BIAS measurement facility........................................................................... 20
7.4 Replacing the tubes ..................................................................................... 23
7.5 Running in the tubes.................................................................................... 23
7.6 Tube service life........................................................................................... 23
8. Using Black Box or Super Black Box........................................................... 24
8.1 The Black Box option................................................................................... 24
8.2 The Super Black Box option ........................................................................ 25
9. Troubleshooting ........................................................................................... 26
10. Specifications and dimensions..................................................................... 27
11. Frequently Asked Questions (FAQ)............................................................. 30

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1. DESCRIPTION OF THE RE 290
The new Octave RE 290 stereo power amplifier is a push-pull pentode design delivering 2 x 100 W
RMS output power (into 4 ohms loads). As with all Octave models, all research and development
(R&D) and production has been conducted exclusively in-house, and the amplifier is
comprehensively safeguarded against user error and parts wear – including catastrophic power
tube failure.
The RE 290 is based on the stable and reliable electronic circuits of the RE 280 MKII model, while
incorporating the benefits of the recently-developed KT120 power tube. The KT120 allows an
output power of more than 100 W via two tubes in push-pull mode, while its current capacity is
higher compared to the classic KT88 tube designs. Increased stability with difficult, low impedance
speakers is achieved through the increased bandwidth and OCTAVE’s specially designed output
and mains transformers.
BIAS Measurement
The RE 290 is fixed BIAS, and utilizes external precision BIAS trim pots and LED confirmation
which allows the user to readily monitor the output tubes and simply correct their BIAS individually
at the front panel of the unit without the need of a micrometer let alone any special knowledge or
tools – just the supplied 3 mm flat-head screwdriver.
Black Box Option
The RE 290 is fitted with a connector for the optional Octave “Black Box” capacitance modules –
available in normal and “Super” versions. The use of the Black Box or Super Black Box significantly
increases power supply capacitance to stabilize current delivery and reduce impedance interaction
of the load, thus improving dynamic range, separation, depth, soundstage size and articulation.
This enables optimizing the RE 290 in respect to the speaker, which is a tremendous benefit if the
speaker is difficult to drive.
Input Section
Unlike other designs, the RE 290 offers single ended RCA and true balanced XLR inputs with a
very high common mode rejection ratio that eliminates unwanted hum and high frequency distortion
induced in the small signal connection to the preamp.
Power Management
The RE 290 input and output tube heaters as well as its high-voltage rails are logic-controlled to
ensure that the conduction of the output tubes as well as the input stage voltages are constantly
monitored and controlled by the Power Management System, which serves to protect the vital
internal parts (tubes, rectifier, electrolytic caps, switches, etc.) against excessive turn-on current.
This increases the lifetime of not only the tubes, but all power related components as each derives
benefit through this system.
Ecomode
The Ecomode serves to reduce heat and unnecessary power consumption when the unit is
switched on but not in use. After 10 minutes without receiving signal, the RE 290 Ecomode is
activated, turning down the power. In this “sleep” mode, the RE 290 draws only 20 W Idle current.
Therefore, the unit produces no heat while it remains switched on. When a music signal is once
again detected by the RE 290, the Ecomode circuit will power the unit back on, with a short warm-
up/start-up delay (approximately 35 seconds) before the unit will operate.
The Ecomode also serves to increase the lifetime of the tubes, while providing an added benefit of
increased safety allowing the RE 290 owner a level of security against any problems when leaving
the unit switched on.

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2. SAFETY INSTRUCTIONS
2.1. Before you begin
Before using the RE 290 for the first time, remove the grille and install the power tubes! (See
Section 3.2 "Removing the grille"). Replace the grille before switching the RE 290 on.
Operating the amplifier without its protective grille is dangerous and not recommended.
In case of emergency: unplug the unit from the wall outlet
Never use an amplifier that is damaged or faulty. Make sure that no one can use it until it has been
repaired by a qualified service technician. Ensure that there is easy access to the IEC socket and
power cord.
Do not open the case
There are dangerously high voltages and hot tubes inside this equipment. To avoid a burn or the
risk of electric shock, never allow anyone except qualified personnel to open the case.
Servicing and maintenance
For reasons of safety, please ensure that any servicing, repairs or other modifications to OCTAVE
equipment are carried out only by a qualified technician. Always get an engineer to replace blown
fuses with ones of the same type and rating. If your amplifier requires servicing, please ship or take
your equipment directly to OCTAVE or to one of our authorized service centers.
Modifications to OCTAVE equipment
Use "audio grade" fuses and other power cables at your own risk. The use of such devices will void
the warranty. This also applies to the use contact fluids on the tube sockets.
Explanation of the warning symbols:
The lightning flash with arrowhead symbol within an equilateral triangle is
intended to alert the user to the presence of un-insulated, 'dangerous
voltages' within the product's enclosure that may be sufficient to constitute
a risk of electric shock to persons
The exclamation point within an equilateral triangle is intended to alert the
user to important operating and maintenance instructions
Before connecting up
Make sure that the voltage of your amplifier matches your electricity supply voltage.
Grounding
This amplifier is a protection class I device (with an earth conductor). To avoid the risk of electric
shock in the event of a fault, the unit must be grounded. To do this, use the power cable supplied
with the amplifier.

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2. SAFETY INSTRUCTIONS
2.2. Placement
1. Location
OCTAVE equipment is designed strictly for use in a dry domestic environment. Do not use it in the
open air or in damp environments!
Never place plants or liquid-filled containers on your OCTAVE equipment. Take care to avoid
dropping objects or spilling liquids into the case. Should this happen, remove the mains plug
immediately and have your amplifier checked by a qualified service technician.
Condensation may form if the amplifier is taken from a cold environment into a warm one. If you do
this, wait until the amplifier has reached room temperature and is dry before switching it on.
Avoid installing the unit close to sources of heat such as radiators or anywhere that may be in
direct sunlight.
Do not operate the unit near flammable materials, gases or vapors. Avoid areas where there may
be heavy accumulations of dust or where the unit may be subject to mechanical vibration.
Place your OCTAVE amplifier on a stable, level surface.
2. Grille
Never operate the amplifier without the protective grille in place.
3. Ventilation
Make sure that your amplifier has an adequate flow of air around it. If you intend to install your
equipment into a cupboard or on a wall shelf unit, ensure that there is at least a ten centimeter (4
inch) gap between the ventilation slots and the walls all around the amplifier. The rear panel of
cupboards should have ventilation holes to prevent heat build up. Do not rest the equipment on a
soft surface such as carpet or foam sheeting.
2.3. Warranty
OCTAVE can only guarantee the safety, reliability and performance of this unit if modifications and
repairs are carried out by specialized personnel and when the amplifier is operated in accordance
with the instructions contained in this manual.

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3. GETTING STARTED
3.1. Unpack and check the contents of the box.
Package contents standard
- RE 290 serial equipped with 5 x KT120 power tubes
- 5 power tubes packed separately with tube layout diagram
- Power cord
- 4.0 x 100 flat-bladed screwdriver for adjusting the bias
- Owner's manual with warranty card
3.2. Removing the grille
Operating the amplifier without its protective grille is dangerous and not recommended.
To remove the grille:
1. For your own safety, switch the amplifier off using the on/off switch or disconnect the
power cord.
2. Pull the grille upward to remove.

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3. GETTING STARTED
3.3. Installing the power tubes
The power tubes are packed in a separate box in the tube compartment
Insert the power tubes into their sockets as shown on the tube layout. Ensure that you correctly
locate the anti-rotation lug on each of the tubes.
Anti-rotation recess
on the tube socket
3.4. Switching on for the first time – the Soft-Start feature
The RE 290 is equipped with a multi-stage Soft-Start-Turn-On protection circuit which extends
component as well as tube life considerably by protecting against stress caused by typical high
inrush currents during switch on.
1) Check that the Ecomode switch on the rear panel is in the "Eco off" position
2) Connect the RE 290 to the mains. (On new units, this switch is set to "off" at the factory).
3) Switch on the RE 290 using the amplifier’s mains power on/off switch.
The Power-LED next to the mains switch will illuminate.

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3. GETTING STARTED
3.5. Checking the power tubes – setting the BIAS
For the first function check you don’t have to connect the loudspeakers or the preamp.
The trim pots are located next to their respective tubes. Next to each trim pot you will see a pilot
lamp, which shows which tubes have been selected with the bias selector switch. A row of LEDs in
front of the transformer cover assists you in setting the bias correctly. It shows three conditions:
bias too low, correct, and too high.
Before checking the BIAS please wait five to ten minutes. Because the tubes are still cold you
would adjust the wrong BIAS
Turn the BIAS-selector switch clockwise to position V1 = BIAS setting for the tube V1. The LED
next to the tube will illuminate, and one of the three BIAS LEDs will illuminate, normally first the
Minus LED, than the OK-LED.
The LED display:
Ecomode LED Indicating the status of the Ecomode (see chapter 6.4)
Yellow "-" LED BIAS setting of the selected output tube is too low
Green “OK” LED BIAS setting of the selected output tube is correct
Yellow "+" LED BIAS setting of the selected output tube is too high
Red "off" LED Indicates that the electronic protection has switched off the
amplifier (see chapter 6.2)
After an additional 5 to 10 minutes, the BIAS control LEDs will change from yellow to green in case
the BIAS Measurement Electronic is switched to tube 1 for example. This indicates the correct
BIAS. Check all four tubes and switch OFF the BIAS electronic during listening.
If you notice any irregularity (“+” = High BIAS ) in the display please refer to chapter 7.3.
3.6. Connecting other components to the RE 290
1) Make sure that the RE 290 is switched off !
2) Connect the other components in your system to the appropriate sockets on the rear of the
RE290. (See chapter 5 "Rear panel connections".
3) Check that the switch positions on the front and rear of the amplifier are in their recommended
settings.
4) Switch on the RE 290 using the on/off switch and wait a few minutes until the unit is powered.
Now you can listen to music.

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4. FRONT PANEL CONTROLS
Mains Power push button switch
To switch on the amplifier, push the knob. The LED next to the knob lights up gradually.
Important! : Do not pull on the knob when it has been pushed in, as this could damage the
retaining mechanism. Make sure that access to the power switch is never obstructed.
Bias measurement selector switch
Off position: The measurement facility is disabled
Position V1 - V4: The measurement facility is connected to the relevant tubes.
To ensure the accuracy of any adjustments, make sure that the volume
control of the preamp is set to 0.
NOTE:
The RE 290 is equipped with a soft-start circuit and a power-up delay timer.
The amplifier is ready for use after a delay of approximately 2 minutes. Because there are
no relays in the signal path, a low-level, slightly distorted signal from your source
equipment may be heard through your loudspeakers during warm-up. This circuitry extends
tube service life and also protects the power section from voltage spikes and excessive
inrush currents.

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5. REAR PANEL CONNECTIONS
RCA Inputs RCA cinch input
Input for preamplifier (using RCA cinch interconnect)


Ecomode Switch
Eco off: Ecomode automatic is off.
Eco on: Ecomode automatic is on.
During Ecomode ON the Ecomode LED lights up
in green. After 10 minutes without signal the
Ecomode turns the unit down and the color of the
Ecomode LED turns to red.


Input and Muting switch Toggles between the inputs RCA and XLR and the function
“Muting”
Switch up: RCA input is active
Switch central: XLR input is active
Switch down: both inputs are muted.
This position is useful for connecting and disconnecting
cables without switching off the amplifier.


XLR-Input Pin 1: Ground, Pin 2: +, Pin 3 –
Loudspeaker Terminal
Right Channel Binding posts to connect the speaker cable.
Red = positive terminal, Black = negative terminal.
You can connect either 4 mm Banana connectors or spades.
The negative speaker terminal is connected to ground.

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5. REAR PANEL CONNECTIONS
Black-Box-Connector
The (Super) Black Box is an outboard power supply
capacitance upgrade for the power amplifier section
(see chapter 8).
You should switch off the RE 290 using the power switch
before connecting and disconnecting the Black Box!
Power Selector Sliding switch to adjust the output power of the RE 290.
(see Chapter 6.1)
Loudspeaker Terminal
Left Channel Binding posts to connect the speaker cable.
Red = positive terminal, Black = negative terminal.
You can connect either 4 mm Banana connectors or spades.
The negative speaker terminal is connected to ground.
Model identification plate
Model and Serial Number
Mains supply socket
IEC socket with integrated fuse holder.
The fuse is located in a pullout compartment above the
socket. You can open the fuse compartment after removing
the mains plug
Fuse holder
Fuse for 230/240V: 4 H slow-blow IEC Type (5 x 20 mm).
Fuse for 115/120V: 6.3 H slow-blow IEC Type (5 x 20 mm)
Fuse for 100V: 8 H slow-blow IEC Type (5 x 20 mm).

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6. ADVANCED FUNCTIONS
6.1. Power Selector, alternative output tubes
Position „HIGH“: KT120
Position „LOW“: KT88, 6550, KT90, KT100 (EL34 with Restrictions)
The Power Selector allows adjusting the RE 290 in accordance to the output tubes. Position HIGH
is reserved for the standard KT 120 tubes. In the HIGH Position the RE 290 is able to deliver 2 x
100 W RMS Output Power. The slightly weaker tubes type KT 88 or 6550 can be used in the
position LOW. In this position the maximum output power is limited to 2 x 70 W to avoid
overloading these tubes. The rather rare tubes of type KT 90 and KT 100 can be used also in the
LOW position.
The EL 34 can be used in the LOW Position in cases of speakers with an impedance higher than 4
ohms.
Tubes of Type 6L6, KT 66, 5881, EL 519 and EL 156 are not suitable for the RE 290.
Before switching the Power Selector turn OFF the mains push button switch
After switching from power LOW to HIGH and vice versa the BIAS should be corrected in case of
using the same output tubes. Normally there is only a slight correction necessary.
When using different tubes the BIAS has to adjust according to chapter 7.3

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6. ADVANCED FUNCTIONS
6.2. Electronic Protection System
The RE 290 features a comprehensive electronic monitoring and protection system. This system
will automatically switch off the RE 290 in case of a fault occurring in the power section.
The protection system has been designed to keep the unit safe from the consequences of
overloads of any kind and to protect the output tubes from current surges.
The RED “Protection” LED lights up to indicate that the protection system has tripped.
The amplifier will not play music once the protection system has tripped and you will
not be able to check or adjust the BIAS setting.
The BIAS LEDs will show "yellow" for each of the four output tubes.
If a Black Box or a Super Black Box is connected to the RE 290, the front panel (operate) LED of
the Black Box / Super Black Box will go out. If the Super Black Box is connected, tripping the
protection system will automatically activate the discharge circuit of the Super Black Box (see
chapter 8.2).
The following conditions can cause the protection system to trip:
- Overdriving the RE 290 to excessive levels or with excessive levels of low frequency.
- A speaker cable short circuit while the speakers are being driven at high listening levels.
- A fault in one or more of the output tubes.
- A fault in one of the preamp tubes which overloads the affected channel.
Once the protection system has cut in, the only way you can turn the RE 290 back on,- is to turn
the on/off switch off and then on again. Allow the unit two minutes to cool down before switching it
back on. If possible, identify and eliminate the cause of the problem (see chapter 9
"Troubleshooting").
If it is not clear what has caused the protection system to trip, we recommend that you check the
BIAS before attempting to use the amplifier again. Tube faults can often result in widely varying
BIAS settings. When these settings exceed a particular value they can cause the protection system
to trip.
6.3. Soft-Start, Inrush current limitation
The RE 290 input and output tube heaters as well as its high-voltage rails are logic controlled to
ensure that the conduction of the output tubes as well as input stage voltages are constantly
monitored and controlled by the Power Management system to protect the vital internal parts
(tubes, rectifier, electrolytic caps, switches, etc.) against excessive turn-on current. This increases
the lifetime not only of the tubes, but also the caps, while all power related components derive
benefit through this system.
The Soft-Start is always activated within the first 60 seconds after the unit is switched on. During
this time you cannot listen.
During the Soft-Start-phase, adjusting the BIAS is not possible.

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6. ADVANCED FUNCTIONS
6.4. Ecomode (power saving mode)
The Ecomode serves to reduce heat and unnecessary power consumption when the unit is
switched on but not in use. After 10 minutes without receiving signal, the RE 290 Ecomode is
activated, turning down the power. In this “sleep” mode, the RE 290 draws less than 20 W Idle
current. Therefore the running unit produces no heat, because the heater voltage and the high
voltage for the power amplifier section are switched off. When the music signal is once again
sensed by the RE 290, the Ecomode circuit will turn the unit back on, with a warm-up/start-up delay
of approximately 30 seconds before the unit will operate.
The Ecomode also serves to increase the lifetime of the tubes, while having an added benefit of
improved safety allowing the RE 290 owner a level of security against any problems when leaving
the unit powered on. The Ecomode is a safety and energy-saving feature that automatically
switches off the amplifier's tube circuitry during breaks of more than 10 minutes.
Ecomode reduces the overall power consumption of the amplifier to under 20W, compared with
180W in normal operation. When detecting a signal, the RE 290 reactivates automatically and is
ready for use again within 30 seconds.
Eco off: The Ecomode function is off, the
Ecomode LED doesn’t burn
Eco on:
The Ecomode function is activated.
The Ecomode LED lights up in
GREEN.
After a 10-minute silence, Ecomode
turn the Unit down. The Ecomode
LED changes to RED indicating that
the Ecomode circuit is powering
down the unit.
Note:
If you switch the RE 290 on with Ecomode active, it will go through the start procedure. If it fails to
detect a music signal, it will shut down after 10 minutes.
Ecomode is not the same as standby, however, because certain sections of the amplifier remain
on.
Important!
You cannot adjust the BIAS in Ecomode once the amplifier has powered down! Powered
down during Ecomode is indicated by the Soft-Start-LED.
The signal switching level of 0.5mV results in approx. 40µW output power of the RE290. In
case of a speaker with a high efficiency an adjusted listening level can be lower than this
value. The Ecomode would drive the unit down. In such cases the Ecomode should be
switched off

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7. TUBES
7.1. Removing the grille
Operating the amplifier without its protective grille is dangerous and not recommended.
To remove the grille:
1. For your own safety, switch the amplifier off using the on/off switch or disconnect the
power cord.
2. Pull the grille upward to remove.
See chapter 3.2.
7.2. Tube layout
V1
V2 V3
V4
V7 V6 V5
Output tubes: V1 - V4: KT 120 TS standard
V1 + V2 left channel
V3 + V4 right channel
Driver tubes: V5, V6, V7 ECC802 (= ECC 82,12 AU 7, 5814, 6189)
In position 5 and 7 the use of the 12 BH 7 is allowed.
V 6 should have a system Gain match close to 0.2dB

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7. TUBES
7.3. BIAS measurement facility
The BIAS measurement facility makes it easy for you to check and adjust the idle current of the
output tubes. Getting the BIAS setting right for all four tubes is critical for both the sound of the
power amplifier section and for the service life of the tubes. This feature guarantees consistent
sound quality over the entire lifetime of the output tubes.
That is why we have built this BIAS measurement facility into the RE 290 – to allow you, the user,
to carry out the adjustment yourself without the need for test equipment. The use of precision op
amps makes it possible for you to set the BIAS to accuracy within 0.2%, making it superior to any
other method.
Using selected output tubes only makes sense if the idle current is adjusted accurately, as is
clearly shown in Fig. 1 Technical Data.
The LED display:
Ecomode LED indicates the status of the Ecomode Electronic
Yellow - LED indicates that the BIAS is Low
Green OK LED indicates that the BIAS has the correct value
Yellow + LED indicates that the BIAS is too high
Red OFF LED indicates that the Protection Electronic has turned off the Power supply of
the Tube section

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7. TUBES
How to set the BIAS
Make sure that no signal is playing through the amplifier when you are adjusting the BIAS. It is
sufficient to turn your preamp volume control to 0; there is no need to disconnect the speakers.
The tubes should have reached operating temperature. The unit should run at least 15 minutes
before you adjust the BIAS. If you notice high BIAS at one or more of the output tubes in cold state
you should reduce the BIAS in any case.
Procedure:
1) Turn the volume control on your preamp to 0.
2) Set the bias selector switch to V1. The green LED next to the trim pot for tube V1 will light up
to show that you have chosen to adjust the bias for tube V1.
3) The bias setting for this tube is correct when the green OK LED on the display illuminates.
If the yellow + LED illuminates, the bias is set too high.
Turn the trim pot counter-clockwise until the OK LED illuminates.
If the yellow - LED illuminates, the bias is set too low.
Turn the trimmer clockwise until the OK LED illuminates.
Repeat this procedure with the other three tubes
4) Switch the bias selector back to its "off" position.
If there is no change in the BIAS of a tube while turning the BIAS regulator, the corresponding
output tube is faulty.
Note:
It is not possible to adjust the bias if the amplifier's electronic protection has
cut in (as indicated by the red "off" LED in the display), or if the Ecomode has
powered down the unit. When you activate the measuring facility under these
circumstances, the-LEDs will illuminate for all tubes. You must fix the fault or
switch off the Ecomode before using the measuring facility. If a defective tube
is causing the problem, you should locate and replace it. (See Troubleshooting
Chapter 9)