Remote Computer Analysis; Locating Defective Ram - HP 330 Service Handbook

Remote Computer Analysis
The Model 330/350 computers provide for remote analysis of problems
by means of the beeper. To test the computer remotely, follow this
procedure:
1. Establish a telephone connection with someone at the location of
the computer.
2. Have them hold the receiver near the speaker output of the com-
puter. The speaker is located in most monitors, or in the speaker
module.
3. Now have them turn the comput.er on.
4. The computer will go through its self-test and report problems as
a series of beeps. These beeps correlate with the above error codes.
5. The beeper annunciates the seven least significant bits. A high
beep indicates a one and a low beep indicates a zero.
For example, suppose that on power-up a computer emits three low
beeps, a high beep, two low beeps and a high beep. This will be of the
form
000
eooe,
where
0
represents a low beep,
e
represents a high beep
and x represents an unbeeped high or low. Referring to the table of
Boot ROM Error Codes shows a RAM Failure as the probable cause.
Locating Defective RAM Boards
Remember that RAM is on the Model 330 processor board in addition
to the 4, 8, 16 Mbyte RAM assemblies.
A RAM failure message may be decoded to determine which RAM block
caused the failure. For example, in the message
Memory Failed at FFB3A900
W:F58A8C2C.R:F78A8C2C
the failure occured at memory address FFB3A900. To correlate this
with a RAM board, take the first three hex digits of the address and
translate them into binary. Then find a board whose address switches
are set to the first ten bits of the top address in that 4 Mbyte address
block.
Troubleshooting
43