Explanation of Diagnostic Lights on 3b2/400
Eric J. Nihill
eric at sactoh0.SAC.CA.US
Sun Nov 18 16:21:19 AEST 1990
In article <1990Nov17.040047.21053 at ox.com> jih at ox.com (John Hritz) writes:
>
> I have a 3b2/400 that has crashed. Upon cold start, the power comes
> up and the diagnostic light blinks 5 times, pauses briefly and then
> repeats. The system never checks the floppy, so it is not possible
> to use the boot disk. Any info on what this diagnostic light
> sequence means would be helpful.
>
Display Possible Causes/Solution
-----------------------------------------------------------------------
Red LED pulsing Unknown problem. The console may be wired
1 time. incorrectly or there may be other trouble
not revealed by LED pulses. Investigate
further using diagnostics and the powerup
trouble shooting chart.
Red LED pulsing Problem with CPU.
2 times.
Red LED pulsing Problem with firmware (ROMS).
3 times.
Red LED pulsing Problem with RAM.
4 times.
Red LED pulsing Problem with the DUART.
5 times.
Both Red and Green Reseat Mmemory boards, I/O Backplane. Remove
LEDs on. feature cards. Try to reboot. Disconnect the
battery and reconnect, then reboot. Swap
first memory card.
Green LED on, Red Check to see that the console is connected
LED off after a correctly. It should have a Term/Printer
short time. Adapter hooked hooked to the MODEM port.
Terminals other than AT&T Teletype may not
supply DTR as a positive 12 volts. Usa a
RS-232-C breakout box to verify, or jumper
pins 8 to 20 in the Term/Printer Adapter.
Source of information:
AT&T 3B2 Computer Maintenance Reference Manual, Issue 2.
Tel #1-800-432-6600
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