Re: Apple IIpluse motherboard problem

[russotto@grace.speakeasy.net (Matthew Russotto)]

In article <1d8358aae4041a6c7eba504d546064b0.10725@mygate.mailgate.org>,
Vince Briel <vbriel@yahoo.com> wrote:
> 
>> Sounds like the 6502 isn't running at all.  Somewhat hard to test without a
>> scope.  Have you tried a manual reset?
>
>I can understand the 6502 not running, but I swapped it with a working
>one and it does the same thing.  The 6502 from the non-working board
>works great in the known working ][plus.

I'm not saying there's something wrong with the 6502, only that it
sounds like it isn't running at all.  Shorting the phase lines can
do that (found out the hard way), as can a lot of other things.  But the
first thing I'd look for is a problem with the power-on reset
circuitry.  IIRC, the 6502 just won't run without an initial reset.  

>Could the 555 timer chips cause the problem?  Or the crystal? I'd like
>to get this board running to have a spare onhand.

Can't be the crystal, or you wouldn't have video. 

-- 
Matthew T. Russotto                                mrussotto@speakeasy.net
=====
Dmitry is free, but the DMCA survives.             DMCA delenda est!
"Extremism in defense of liberty is no vice, and moderation in pursuit
of justice is no virtue."