17 Jan
2004
17 Jan
'04
4:53 p.m.
Just a quickie folks,
Does anyone have the power cable pinouts for the Osborne 1 motherboard? Got
one here from Kevan that doesn't boot at all - consistent garbage on the
nice'n'bright screen. Before I start further messing with the beast I want
to make sure it's getting enough juice. Suppose I can always check the CPU
and RAM chips for +5V couldn't I - it's been powered up in this condition in
Yes, that's what I'd do. Check the 5V line at a known chip (CPU, or a TTL
device). In a machine of this type, there'll only be one 5V line (unlike
in my 11/45 where there are several, from separate PSU bricks...).
I don't know what the RAMs used are, but if they're 3-rail types, like
4116s, you should check the other supplies there too.
If the PSU lines look good, then check that the CPU is getting a clock
signal. Look also for activity (changing singals) on the address and data
lines from the CPU.
-tony