3B2 problems galore

[Philip A. Gross]

Graham Glen (Technical Manager) <netsys!pyrdc!uunet!qukmips!graham> writes:

>> 
>> reason. When I try to boot them, the power light comes on and stays on, but
>> the diagnostic light goes "flash, flash, flash, flash, flash, flash...pause"
>> and repeats this pattern over and over. Somebody here at Tech who has worked
>> rather extensively with the 3B2s suggested that maybe the boot ROMs were bad.
>> I swapped out the ROMs with known good ones, but nothing changed.
>> 
[...stuff deleted...]
>> press the RESET button, then the power light comes back on and the diagnostic
>> light begins flashing as before. The DIAGNOSTICS won't run at all.
>> 

>I have had exactly this problem before. In my case, I swapped parts from a
>known working system until I had replaced the entire machine, and it still
>would not work. The reason I found in the end was that the cable from the
>terminal to the console port had got damaged, the machine was not seeing a
>complete set of hardware handshaking lines, and so refused to play ball.

>Try swapping the console cable for another one which you know works, and
>also put a breakout box on the terminal to check whether all the necessary
>handshaking lines are being generated. It may cure the problem.

>Graham

Just got back from vacation and stumbled across this problem.  I am
not sure if you have had any worth while replies but here is my 2 cents.

Graham is correct here in stating that their may be a problem with the
3B2 communicating with the console.  We have this same problem crop up
occasionally when we need to reboot the system, it has always been
remedied with a simple press of the RESET button.  However, if you
are getting SELF CHECK, then console wiring is not the problem.

If you are still having trouble with identifying the problem, below
is a list of the what the flashing diagnostic led means.  These are
quoted from the AT&T 3B2 Computer Maintenance Reference Manual.

1 pulse		Unknown problem. The console may be wired incorrectly
		or there may be other trouble not revealed by LED pulses.

2 pulses	Problem with the CPU.

3 pulses	Problem with firmware (ROMS).

4 pulses	Problem with RAM.

5 pulses	Problem with the DUART.

A suggestion that is made later in the manual is to push down firmly on all
socketed components on the system board as well as reseating all of the
boards.  Heat generated from the processor's will often cause chips to
"creap" out of their sockets and then if the system is moved, a chip
may break electrical contact with its socket.

If none of these measures work, then you may have to dust off your wallet.

===============================================================================
Philip A. Gross       The Computer Solution Co., Inc.       Voice: 804-794-3491
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        The opinions expressed here are strictly mine and nobody elses.
        << I haven't heard what I have to say about that yet. >> :-)