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Posted Sun Feb 19, 2017 12:07 AM
Posted Sun Feb 19, 2017 2:16 AM
When a games does not start, try hitting the "reset" button. If that does not help, it could be the fast power-on reset circuit. The fix for that is to change the capacitor or resistor in the reset circuit to make the reset in the CV a little longer so the F18A has time to finish configuring the FPGA at power-on before the CV tries to initialize it. I can't remember the capacitor designation off-hand, I'll have to look it up.
There are also some reports of the F18A not working in some EU/PAL CVs. I have one of these CVs and I am actively working on troubleshooting what the problem might be with those specific consoles.
Posted Sun Feb 19, 2017 12:37 PM
Posted Sun Feb 19, 2017 12:46 PM
Posted Sun Feb 19, 2017 12:56 PM
Posted Sun Feb 19, 2017 1:30 PM
Posted Mon Feb 20, 2017 3:05 PM
The scrambled image above looks like a problem due to the fact power-on reset of the CV. Replacing C3, as Bmack36 specified, with a 10uf cap should help correct that problem.
I have a EU PAL CV motherboard (thanks to an A.A. member loaning me one) and I am actively trying to find out why these motherboards are having problems. The main symptom is the screen going black after the difficulty selection screen. The reset button does not correct the problem, only a power-cycle can bring the system back.
It is *not* a BIOS problem. I have swapped an NTSC BIOS with the EU BIOS, same symptom. I have also swapped the Z80 CPU, since the EU board had a Z80C and the NTSC board I have uses a Z80A. No change, the problem follows the motherboard.
The problem also seems to be time-related. I can power up the board cold after sitting for a while and the game (I'm testing with Donkey Kong) will start fine. Then over the next few minutes, if I power cycle or reset the console, the problem starts to come on slowly. First, there are the graphic anomalies about Kong (blue pixels in places), then after a few more resets the game will lock up after the difficulty selection screen.
To me this represents a component slowing failing over time, and it is fine until it warms up. This is just a theory at this point, but I'm working on narrowing it down. However, so far it is not:
1. The BIOS
2. The CPU
3. The power supply brick (I'm using the same power brick for both my NTSC and EU boards)
4. Joystick (I'm using the same joystick in the same port when testing)
Posted Tue Feb 21, 2017 5:15 AM
OK if it's not the BIOS then is it the 50Hz output for PAL / SECAM TV signal?
Both run at 50Hz instead of 60Hz. At some point the signal surely has to be buffered and dumped to the screen (assuming the motherboard crystals are the same).
Just a thought....
Posted Tue Feb 21, 2017 12:10 PM
Posted Tue Feb 21, 2017 12:29 PM
If the problem goes away after hitting the reset button after powering up, then the 10uF cap will fix it. If it does not get better after hitting reset after powered up, it will not.
Posted Wed Feb 22, 2017 12:37 AM
The 10uf cap does help make the video output reliable in that it boots to the VGA screen every time instead of it being hit and miss. It is the actual output once Matthew's board is running when you select and try to play the game. The issue is in the Colecovision itself....
Posted Wed Feb 22, 2017 11:00 AM
Posted Thu Feb 23, 2017 7:11 AM
Posted Fri Feb 24, 2017 6:33 AM
Posted Fri Feb 24, 2017 10:29 AM
Posted Fri Feb 24, 2017 12:13 PM
Posted Fri Feb 24, 2017 12:23 PM
The issue is startup delay. The F18a needs a little more time to load and get ready for operation. By changing the C3 capacitor from 1uF to 10uF, the startup time for the coleco is increased which allows the F18a to be ready in time.
Posted Fri Feb 24, 2017 3:51 PM
@Mika73. The 10uF cap C3 is on the CV motherboard, not the F18A.
The problem is *not* the BIOS. See my update post #9 above. I put the NTSC BIOS in the PAL CV motherboard and have the same problem. I also put the PAL BIOS in my NTSC CV motherboard and do not have any problem.
Edit: It is not the 50Hz vs 60Hz frequency either. The CPU on both systems run at *exactly* the same frequency (I have measured both). The 50Hz/60Hz is created with a tuned R/C circuit that is driven by the main system clock. The only place the 50Hz/60Hz are used are as inputs to the original VDP, and those clocks signals are not used by the F18A.
Edited by matthew180, Fri Feb 24, 2017 4:17 PM.
Posted Sat Feb 25, 2017 12:40 AM
Posted Sat Feb 25, 2017 12:52 AM
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