6-77
Either the battery is defective or the detecting circuit is defective.
4720 LOW:
WARNING
I
When replacing the lithium battery, avoid personal injury by observing proper methods for
handling and disposal. Improper handling may cause fire, explosion, or severe burns. Don't
attempt to recharge and don't crush, disassemble, heat the battery above 212°F (100
°
C),
incinerate, or expose contents of the battery to water. Dispose of battery in accordance
with local, state, and national regulations.
3. If the battery voltage is too high or the voltage to ground from the
+
lead is too high, check
A12CR802. To ensure continued proper operation of the NVRAM, replace A12BT800 after
correcting the overvoltage condition.
2. If ok, test for the same voltage range at A13U700 pin 21. If ok there, replace A13U700. If voltage
is wrong at pin 21, backtrack to the problem component (suspect A12U490).
1. Measure the battery voltage directly across the battery (BT800) and check for a range of 2.5 V to
3.5 V. If ok, then test from the + lead of BT800 to ground for the same or less voltage.
Either the voltage is really high or the detection circuitry is defective.
4710 HIGH:
Troubleshooting Procedure:
There is no hardware exercised for this test. The operating system is informed by the front panel pro-
cessor if the battery voltage is either high or low. The "test" is to read a memory location where the
System ~P has stored the status after checking with the FPP. If the status is unknown, the result is
NULL. If the test "passes," it means that it is not defective in that direction.
Testing Method:
Battery A12BT800 (NVRAM keep-alive battery) (schematic diagram 1):
4700
BATT STATUS
4. Display REF1 and check for a 10100101 pattern coincident with the enable pulse at U751 pins 3,
6,7,9,12,14,16, and 18. If not ok, replace U751.
3. Display REF1 and check for a 10100101 pattern coincident with the enable pulse at U751 pins 17,
15, 13, 11, 8, 6, 4, and 2. If not ok, replace U700.
2. Check the enable pulse at U751 pins 1 and 19. Save and move to REF1.
1. Check for a pattern of 10100101 at U742 pin 19, 16, 15, 12,9,6,5, and 2 at the rising edge of
the trigger strobe (Word Recognizer Probe is useful for this check). If not, and U742 pin 11 is LO,
then replace U742. If U742 pin 11 is HI, replace U700.
4600 A13U742/A13U751:
3. Check A12U654 pin 13 for LO. Replace A12U654 if pin 13 is LO and test is failing.
2. Check for LO at U861 pin 6; replace U861 if pin 6 is HI.
Table
6-6
(cont)
Maintenance-2430 Service
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