tmcw
New member
Got an untested R8731 (Revision B) the other day.
It's pretty much a Rev-B, except that it has the 2G chip taken out, a socket put in, and a little daughterboard inserted into the socket, the daughterboard having a chip (N8T97N 8131) and a SIP resistor package, I presume to make the board similar to the Rev C and D MPU boards?
It originally had 4116's, and when I initially tested the board, I was getting RAM errors, and was able to move the error around, but didn't spend much time on that, as I planned on modding the board to take 4164's.
Did the 4164 mod today, and put the board into the game (Stargate, all other boards and power supply working correctly), get the "all systems go" message, "0" on the ROM board, but the game then displays a message about "adjustment error".
If I press advance at that point, it goes to the game, and I can play, etc., but the high score screen is fully populated with scores of 888,888, and no inititals. When I begin a game, I have more than about 18 ships and smart bombs.
In the game adjustments, the settings for extra men, etc, have values like 98,888, or other ridiculous values like that. One thing I did notice was that with batteries in (giving 4.1V), I was able to set the game to freeplay, and it seems to be retaining that adjustment.
In game diagnostics, it passes the RAM and ROM tests, but I then get a CMOS error message.
Is this definitely pointing to a bad CMOS chip, or is there anything else I need to check first?
I pulled the decoder ROMs and 6809 off the board and tested them in a good board, and they functioned fine. Also checked traces off the CMOS chip to where they should go, and they checked out fine too.
It's pretty much a Rev-B, except that it has the 2G chip taken out, a socket put in, and a little daughterboard inserted into the socket, the daughterboard having a chip (N8T97N 8131) and a SIP resistor package, I presume to make the board similar to the Rev C and D MPU boards?
It originally had 4116's, and when I initially tested the board, I was getting RAM errors, and was able to move the error around, but didn't spend much time on that, as I planned on modding the board to take 4164's.
Did the 4164 mod today, and put the board into the game (Stargate, all other boards and power supply working correctly), get the "all systems go" message, "0" on the ROM board, but the game then displays a message about "adjustment error".
If I press advance at that point, it goes to the game, and I can play, etc., but the high score screen is fully populated with scores of 888,888, and no inititals. When I begin a game, I have more than about 18 ships and smart bombs.
In the game adjustments, the settings for extra men, etc, have values like 98,888, or other ridiculous values like that. One thing I did notice was that with batteries in (giving 4.1V), I was able to set the game to freeplay, and it seems to be retaining that adjustment.
In game diagnostics, it passes the RAM and ROM tests, but I then get a CMOS error message.
Is this definitely pointing to a bad CMOS chip, or is there anything else I need to check first?
I pulled the decoder ROMs and 6809 off the board and tested them in a good board, and they functioned fine. Also checked traces off the CMOS chip to where they should go, and they checked out fine too.
