Date   : Thu, 25 Jun 2009 10:47:44 +0100
From   : chris@... (Chris Long)
Subject: Only one beep

Hi all,

New member here... I'm trying to get my old model B working - it's my 
original one from the early 80s that I've recently got out of storage.  
It's not working reliably so I'm hoping to get some troubleshooting tips.

A coulpe of months ago, I switched it on and it started up fine, showing 
the usual welcome notes and command prompt.  I had barely had time to 
type '10 PRINT "HELLO" 20 GOTO 10' before it froze up and would not 
reboot.  I suspected a loose connection going bad as the machine heated 
up, but since then it has refused to start up even from cold.

The current syptoms are that, on switching on, I get the first low beep 
but not the second higher beep - does that indicate a specific fault?  
The caps lock LED coms on, and toggles as expected when I press the CAPS 
LOCK key.  The video displays nothing but a grey smudge at the top of 
the screen.  I can hear the usual faint buzz from the speaker that I 
remember was always present.

I've checked the PSU outputs with a multimeter, getting +4.8 volts on 
the +5 lines and -5.7ish volts on the -5 line - are these voltages 
within limits?  I don't have an oscilloscope so can't check any timing 
signals etc.

Any pointers would be gratefully received.  The machine has a debugger 
ROM in it which may prove historically interesting if I can ever get the 
thing working!

Cheers,

Chris.