alessio
New member
Missile command stuck in test mode (bad INT signal)
My MC always boots in test mode and the screen keeps flashing as one (or more) button is continously pressed.
Compairing my PCB with a working one I've found that INT signal has the right frequency but the active time is twice the expected. (let's say that in the working PCB INT is active for one mSec while mine is2 mSec)
INT is generated by the 7474 @F7, the flip flop inputs are ok thus is INTACK that is not working properly.
I've replaced the decoder @M5 but the problem persists.
Sincerely I don't know if the wrong INT signal is the cause of my problem or jit's ust a side effect.
What should I check?
Note:
- voltages are ok;
- new Rom sockets
- Roms checked
- rams socketed and replaced with brand new ones
- micro, pokey and prom are ok
- all the address decoding ICs have been replaced (N2, P2, M5, E8)
- all buffers checked and working
- test switch ok
- all switches are ok
My MC always boots in test mode and the screen keeps flashing as one (or more) button is continously pressed.
Compairing my PCB with a working one I've found that INT signal has the right frequency but the active time is twice the expected. (let's say that in the working PCB INT is active for one mSec while mine is2 mSec)
INT is generated by the 7474 @F7, the flip flop inputs are ok thus is INTACK that is not working properly.
I've replaced the decoder @M5 but the problem persists.
Sincerely I don't know if the wrong INT signal is the cause of my problem or jit's ust a side effect.
What should I check?
Note:
- voltages are ok;
- new Rom sockets
- Roms checked
- rams socketed and replaced with brand new ones
- micro, pokey and prom are ok
- all the address decoding ICs have been replaced (N2, P2, M5, E8)
- all buffers checked and working
- test switch ok
- all switches are ok
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