That pesky Jupiter Ace *still* won't work...t

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Sun Jun 1 14:35:01 2003

> In message <m19MAeX-000IznC_at_p850ug1>
> ard_at_p850ug1.demon.co.uk (Tony Duell) wrote:
>
> > So what haven't you replaced yet? That could be a good starting point for
> > what still might be blown...
> Only the components from the video timing chain.

You have a 'scope, and the outputs of the timing chain should be pretty
regular, so it's not hard to ensure it's clocking correctly... You have
checked the CPU clock, etc, are presnet, right?

> It is possible that some of my repairs to the board may have shorted out.
> These repairs were concentrated around the RAMs, more or less. $DEITY knows
> how I'm going to test for that...

An ohmmeter ? :-)... Check for shorts between adjacent pins/tracks, and
the like

More seriously, look for signals on RAM pins that don't look like clean
TTL signals. If you find any, make sure you have not got 2 signals
shorted together.

You mentioned earlier that the ACE only loads the chargen after checking
program RAM, etc. What does it do if the test fails? HALT? Goes into a
tight loop? Can you see if it's getting there with the 'scope (if it's a
tight loop, most of the address pins should be static, at least during
MREQ cycles).

-tony
Received on Sun Jun 01 2003 - 14:35:01 BST