On Monday, December 26, 2016 at 5:27:27 PM UTC-8, craigwe...@gmail.com wrote:What was the outcome? Did you get this board operating?
On Monday, December 26, 2016 at 12:06:18 PM UTC-8, pinworks wrote:
On Saturday, December 24, 2016 at 2:16:59 AM UTC-5, craigwe...@gmail.com wrote:
I picked up a Williams system 7 board that will not run on its own. I put in the Leon test ROM and I get a flashing "0" and when I press the diagnostic switch, I get a 1-2-3 then back to a flashing "0"
What I am trying to figure out, I am guessing that this is the indication of a working board, but when I put the game ROMs back in, it is dead.
So, I am kind of stuck. I am thinking that maybe I need new ROMs?.
Does anyone have a copy they can PM me of the Leon instructions?
Leon's test EPROM will cause the output pins of the 6821s to pulse high and low. This true for both 6821s on the mpu board and the 6821s on the driver board. To really take advantage of Leon's chip, you should check each of the output pins of the 6821 - pins 2 through 17 - to be sure they are performing correctly. Leon also runs a simple check on the 6821 to try to find errors in the internal registers.
The one drawback to Leon's test is that it is small. It uses very little space in the chip and does nothing to test the address decoding for the other EPROMs on the MPU.
If you have a situation where his test runs when the other ROMS are removed and his test fails when the other ROMS are in place that either the address decoding chips are bad and are activating the ROMS when they should not or the ROMS themselves are bad and are putting garbage on the data lines. Again, Leon's test does not check the other ROM/EPROMs. If you meant to be talking about the RAM chips, the same holds true, either the address decoding is bad or the RAM chips are bad.
Are the 6821's on the driver board working properly with Leon's test chip? That is the final test of your address and data lines crossing the 40 pin interboard connector.
Pin 9 on Q36 is low, that is why I replaced it. But then after putting in a good 6821, I got the same output from pin 9 (PA7). I see on the schematic that it goes to a jumper which then goes to ground and one end of a 4.7K resistor. I have to check the resistor, But I do not think the 6821 is bad. I think something in the circuit is pulling it down to a low signal instead of a high low like the rest of the pins. I also see that there is a PIA pullup chip IC 37 which is a DIP 10K resistor network. I would not even know where to find that if I had to replace.Just found out that pin 9 IC36 is not used on this CPU. So, I will attempt to change the 2114 ram chips see if that helps.
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