ZETRON 748, Technical Manual

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025-9368H 203
VI REPAIR
WARNING
Repair and/or servicing of this equipment may only be performed by qualified personnel
experienced in telephone, radio communications systems or by qualified personnel at an approved
repair facility.
In case of installation difficulty, call Zetron for a Model 748 Applications Support Engineer. Please
have the serial number of the unit and/or the Zetron order number when you call.
If a unit develops a fault in service and the unit needs to be returned, after consultation with a Zetron
engineer, you must obtain an Authorzed Returns Number (ARN) before returning the unit. Please
quote the ARN in any further correspondence.
Zetron, Inc.
28 Campbell Court, Campbell Road,
Bramley, TADLEY, Basingstoke,
Hants, U.K.
RG26-5EG
Tel No: +44 (0) 1256 880663
FAX No: +44 (0) 1256 880491
MISCELLANEOUS SERVICE NOTES
1. When the unit is reset or powered on, an automatic memory test will be executed. If greater than
20 memory errors are detected in the user programming, the unit will reset all of the user
database to the default settings. Any user with bad checksum will be marked as such and can be
displayed under System Statistics in the Diagnostic menu.
2. If the audio does not sound correct, perform an audio sweep test by generating an audio signal on
the RF input of the repeater (of known deviation), and monitor the repeater output deviation. The
output deviation should be fairly flat from 300 to 2500 Hz.
3. When using the internal noise detector for COR, if the COR polarity switch seems backward, the
audio input from the receiver may not have enough high frequency content (greater than 6 kHz)
for the noise detector to operate. It is usually caused by low pass filtering of the discriminator
audio signal. An alternate connection point must be found in the receiver which provides
unfiltered audio, or a receiver generated COR signal must be connected.