HELP: Williams Comet Display Ghosting Player 1 and 3 displays millions digit
Thanatos
installed in a Williams Comet because the old displays were shot. The
new displays work well except for the millions digit on player 1 and
player 3 have a ghost image on them when they should be blank. I
finally traced the digit as coming from the credit match displays.
The match display data appears to be overlayed and ghosted onto player
1 millions digit, the credit display data is overlayed and ghosted
onto player 3 millions digit.
I have checked all the strobe lines with a scope and don't see any of
them shorted, they are all seperate pulses and in their own time
space.
We have a second Pinscore master display board as a replacement
shipped by them and the same thing!!.
I'm at a complete loss as to what is going on.
One more piece of information, the commas for display 1 show up in
display 3 when playing a 1 player game.
Any help would be greatly appreciated.
Thanks
Thanatos
kbliznick
pin 1 is strobe 1 and controls two digits on the credit display
pin 2 is strobe 2 and contorls the leftmost digit on the player 1 and
3 displays.
also check the resistor array at SR11
and finally check pins 8 and 9 at connector and wiring at 1J1.
Sounds like either an output is leaking at the decoder chip or there
is some battery corrosion damage that is shorting the line for strobe
2.
The commas are controlled directly from the 6821 PIA at U5. Again
check for battery corrosion
Thanatos
I put two channels of the O-scope on the lines right at the master
display connector 4J9 and both signals Strobe1 and Strobe2 look clean,
and their timing is fine as far as I can tell. Since that's the end
of the line for the signals I don't see how anything upstream can be
causing a problem if the signals at the master display are not
distorted.
Also the commas will not appear on display 1 instead they display on
4, unless we play a four player game, then they appear on all the
displays.
No battery corrosion visible, real clean CPU board.
Any one with any other ideas?
It is really strange, nothing on the scope looks out of order.
kbliznick
If you have tried 2 Pinscore displays with the same result then it has
to be your cable or your MPU (try the displays in another game)
Not a lot of components here so if you can't diagnose this with a
scope and you don't see any shorted traces (look for solder blobs or
scratches) then you should start replacing parts.
only 6 possible parts here on the MPU.
a 6821 PIA at U5
the decoder at 74154
2 resistor networks
the connector and cable.
I would start with the cable and connector, then the decoder , then
the resistor networks and the PIA last.
BTW do any of the display data lines run under the battery holder? If
they do it might be good to remove the holder to check underneath.
Thanatos
Yeah, I figure there is no chance that it is the pinscore board, but
for the life of me I can't find anything wrong with the strobe
timing. I did not however look at the relationship between the strobe
timing and the segment data from the CPU, if that is out of wack
because of a bad PIA it could be causing this kind of problem.
I'm also gonna check the ground at the master display board. I was
using a ground from inside the head for the scope, and that could have
given me some false info if the ground from the head is not a good
solid ground, then the master display board might not be able to
interpret the signals properly.
If I don't see anything with that, then I'll switch over to the
shotgun approach :)
Thanks
Thanatos
High Noon
with a pinscore display (PS-10749-P) I installed on a Comet
yesterday. It appears that the match display is overlayed and ghosted
on the millions digit of Player One and the credit display is
overlayed and ghosted onto the millions digit of Player Three.
On Nov 10, 8:31 pm, Thanatos <thanato...@gmail.com> wrote:
> OK, I've got a weird problem All newPinscoreLED displays were
> installed in a Williams Comet because the old displays were shot. The
> new displays work well except for the millions digit on player 1 and
> player 3 have a ghost image on them when they should be blank. I
> finally traced the digit as coming from the credit match displays.
> The match display data appears to be overlayed and ghosted onto player
> 1 millions digit, the credit display data is overlayed and ghosted
> onto player 3 millions digit.
> I have checked all the strobe lines with a scope and don't see any of
> them shorted, they are all seperate pulses and in their own time
> space.
>
> We have a secondPinscoremaster display board as a replacement
