Re: Inverse and Flash don't work :(

[Rubywand <rubywand@swbell.net>]

vega writes ...
> 
> Michael J. Mahon wrote:
> 
> > This sounds like a pre-Revision 7 main board.
> >
> > There are two ICs common to both inverse and flashing character
> > generation,
> > the 74LS02 OR-gate at B13 and the 74S86 XOR-gate at B2.  If I had to
> > choose, I'd try replacing the 74S86 first.
> 
> I've changed  both 74LS02 and 74S06 but inverse and flashing charater don't
> work too.
> 
> > If it were only flashing that didn't work, then the 74LS08 (B11) or the
> > 555(B3) would be the likely suspects.
> 
> I noticed that there are another 74LS08 in motherboard, so I tryed to
> switch them... but again there are the same problem and both inverse and
> flashing character dont work. I will try to change so 555...
> 
 ....

     Might try pulling/replacing the 74LS174 at B-8. If the Bit 7 output
from that chip is staying at 1 (due to poor contact in the socket or
a chip defect), then, the output of the 74LS02 at B-13 would be forced
to 0 and you would have a rough time getting any INVERSE.



Rubywand