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Bias-Probe Octal, KIT

Description

Kit of a bias probe for indirect measurement of the quiescent bias current of a tube. The adapter is placed between the tube and the socket and is connected to a standard voltmeter (not included). Pay attention to the quality of the meter and to sufficiently charged batteries!

The quiescent current is measured indirectly via a precision resistor built into the adapter. The advantages of this measuring method are harmless voltages in the mV range at the measuring plugs as well as short ways for the current, since it does not have to be led through the measuring device (common practice with many measuring adapters of Far Eastern production). As a result, there is no risk of oscillation of the amplifier, which could damage the tubes or the amplifier itself.

Note: This adapter cannot be used when additional tube brackets are installed. These must be removed before using the measurement adapter and reattached after the measurement is complete.

Measurement procedure
Determine the resistance of the adapter, including the test leads. Connect the adapter to the meter, but do not connect it between the tubes and the amplifier. Select the ohms range on the meter and note the reading, e.g. 1.1 ohms.
For the final measurement, insert the adapter between the tube and the de-energized amplifier, connect it to the meter, select the mV range and switch on the amplifier. When the amplifier has reached a stable operating condition, read the value in mV from the meter and calculate the quiescent current using Ohm's law.

Example
Measured voltage = 47 mV, adapter resistance = 1.1 ohms.
Formula (I = V / R) or in this case
Bias Current (in A) = Measured Value (Voltage in V) / Measured Value (Resistance in Ohm)
0.047V / 1.1 Ohm = 0.042A or 42mA

For the calculation of the correct bias current as well as further information on bias measurement please refer to further documents or the bias setting instructions in the info section as well as the manual of the amplifier itself.
This adapter is suitable for all EL34, 6L6, 6550, KT88, 6V6, 6CA7 and other tubes with the same pinout.

Attention HIGH VOLTAGE ! Measurements and work on tube amplifiers should only be done by qualified personnel.

Files:

Datasheet

Manufacturer

Herstellerinformationen | Manufacturer Information

Tube-Town GmbH
Rumbergring 37
D-66969 Lemberg
eMail: info@tube-town.de

Customer reviews (5)

Essential information about customer reviews We do not verify that the published reviews come from such consumers who have actually used or purchased the rated goods or services. All reviews, i.e. positive and negative, are published. No reviews that are unobjective, offensive or unrelated to the product will be published.

Andrea B., 03/24/2024

good quality board, excellent kit, but unusable on amplifiers that have metal elastic tongues to hold the tubes, base diameter of the cup that encloses the board is excessive, I was forced to purchase octal extensions. encloses the board is excessive, I was forced to purchase octal extensions.
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Peter, 02/28/2013

Superb quality ! Really a must-have tool for setting up bias.

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Version 2020, Turretboard Version 2020, with the following additions and extensions compared to the previous version:

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Optimizations in the area of master potentiometers and the circuit design of the first gain stage
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Please visit the >>Project page for more infos about the amp.
We will send the circuit and layout plan of the kit together with the invoice by email after the delivery.

INCLUDED:

Outputtransformer Tube-Town tt-ma18-ot
Powertransformer Tube-Town 18W, 0-120-230-240V @ 50/60 Hz (since 25. Oct. 2019)
FX-Loop
Resistors
Capacitors
Jacks
Light
Wires
Board
Switches
Tubes
Fuses & Fuesholder

NOT INCLUDED:

Chassis
Turrets ( you need 4 x 25 pcs. )
Knobs
Faceplate
Headshell

To build this project knowledge in electric engeneering, experience with high voltage, and the reading and understanding of schematics and dealing with measurement device is highly recommended .
There is NO step-by-step guide for beginners. The circuit and layout plan includes all relevant information. If you don't understand it then don't build it.
THIS IS NOT A BEGINNERS PROJECT !

Files:

Application Notes Turret-PCB

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Bevel-free cutting edges for smooth and sharp cuts
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