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turn had damaged the EEPROM memory store IC402 (AT29C512) on the same PCB. This
resulted in spurious behaviour and the inability to change memory contents.
Both components had to be replaced, and it is suggested (by AOR Japan, the equipment
manufacturer) that two additional diodes (1N4148 or 1SS1588 or 1SS266) are inserted in series
with the un-switched 12V line between connector J403 and the regulator IC410... this is best
achieved by a cut in the track between the unused +ve pad of C426 en-route IC410. It is likely
that the 'system data' may need to be reinstated after component replacement, using a modified
version of the EM8200 slot card (referred to as an AR8600 workshop tool).
Additional series diodes have been fitted to all new stock equipment in recent months to increase
robustness of the power supply circuit (for occasions where an over-volt connection is
encountered).
If you require further clarification, please request that your supplier pursues the matter through
their 'distribution chain' of supply as this level of information falls outside the scope of a simple
technical bulletin.
Low batter indicator (BP8600)
If you have the optional internal NiCad battery (BP8600) fitted, the low battery indicator circuit
may not function when the above modification is applied.
Change the following resistor values to restore normal operation:
R446 should now be 56k OHM (was 100k OHM)
R447 should now be 100k OHM (was 68k OHM)... you can use the resistor taken from
R447
The change in value is due to the voltage drop presented by the series diode. The indicator
should turn on when the battery voltage drops around 8.2V to 8.3 V. If you are not using the
internal battery, ignore these component value changes. If you do not change the components,
no damage will occur, the set will simply stop working when the BP8600 battery runs flat -
without warning.
*
Note regarding power supply voltage when using BP8600
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