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DISTRIBUTION AMPLIFIER/ZONE MIXER/MIC SPLITTER DA-410.
Next paragraphs details some of the most frequent fixes as a guide to the qualified technical
service helping to repair the unit:
If a fuse break due to a mains transient or when the unit has been connected accidentally to 380
line voltages, replace it with the same ratings as described before. If it breaks again, check the
overvoltage protections placed on the voltage selector. If broken, substitute them by an equivalent
part (130 volts VARISTOR).
If the power supply fails, the unit will remain in MUTE mode. In this case it is necessary to check
the rectifier bridge (D50), the filter capacitors (C99, C100, C101, C103 and C115) and the regulators
(U25, U29 and U32). Keep in mind that if the unit has been turned on, the regulators heatsinks could
be hot, with the rising danger of burns.
Upon changing the damaged element, it is necessary to ascertain that no element is
overheating in the main board, since this can be origin of the problem.
The potentiometers have a limited live span; they could become dirty and produce noise upon
moving them. It is important that you don't use sprays cleaners over the potentiometers, since they
can become damaged shortly. We recommended cleaning it by compressed air only.
In order to change a potentiometer, the unit must be opened. Care must be taken when
removing the bottom cover as the line transformer is attached to it.
To remove the front panel, extract all five visible screws. The sub-panel behind the front panel is
joined to the chassis by four screws located in the chassis sides and by the potentiometers. Special
care must be taken when re-install the front panel because some delicate parts as the LED lamps
must be introduced in small panel holes and it is a not easy operation.
Normally the signal reductions in the distribution amplifier/zone mixer/mic splitter are produced
by three causes: the LEVEL potentiometers, the unbalanced circuit and the electronic balanced one. In
the unbalanced and electronic balanced circuits, a signal reduction around 6 dB reveals that one
halves of the circuit has any trouble. The LEVEL potentiometers failures gives also sudden random
signal reductions as well as swinging signals.
10. APPLICATION EXAMPLES
In the following schematic drawings are represented three of the more common applications of
the unit:
Distribution amplifier: For signal buffering and remote distribution.
Zone mixer: Dedicated mixing to separate ambient locations.
Active splitter: Microphone/Line splitting for optimal, noise free large sound systems.
DISTRIBUTION AMPLIFIER APPLICATION EXAMPLE
In the distribution amplifier example application, we have supposed a conference session
that should be transmitted to several televisions and radio stations.
A mixing console (two for system redundancy), processes all the microphone and line
signals involved in the session. The output console output and the redundant system if needed,
drives the DA-410 inputs. In this case, we configure the inputs in LINE mode operation. The
distribution amplifier then buffers the selected signal A or B to each one of the televisions and/or
radio stations separately. MONO switch allows us to convert the stereo signal provided in order to
adapt them to monophonic equipment.
In case of the main system failure, simple selection of B redundant system restores signal
transmission quickly.
The use of input (IT-DA) and output (OT-DA) transformers is recommended in order to provide
a galvanic isolation with the television and/or radio systems.
