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Got F18A installed some games don't work/black screen


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#26 Mika73 OFFLINE  

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Posted Sat Feb 25, 2017 1:04 AM

But if it would... Then Colecovision PAL model should work with US PSU and it won't... Don't know if anyone try US Coleco with Euro
PSU and F18A if there's problem..


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#27 Sparkoids OFFLINE  

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Posted Sat Feb 25, 2017 3:22 AM

Is it possible that it has something to do with US and EU power supply difference. US it's 60hz and Europe 50hz. Just come to my mind...

http://www.djtelectr...z-Frequency.pdf


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It won't be because Matthew is (I presume) a 60Hz PSU..



#28 matthew180 OFFLINE  

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Posted Sat Feb 25, 2017 7:34 PM

Correct, I mentioned in my post #9 update that I am using the same power brick (a U.S. 60Hz) for both the PAL and NTSC motherboards.  It is the only power brick I have.

 

I observe the problem with games that do not enable the VDP interrupt until after the difficulty screen.  Donkey Kong is one such game.  However, games like DK Junior work on both machines all the time and the interrupt is active from the title screen.  On the PAL CV I have, the problem also degrades after the unit has been on and reset several times, which is why I think it may be a failing component of some sort.  But I'm still not sure or convinced.



#29 matthew180 OFFLINE  

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Posted Thu Mar 16, 2017 11:04 AM

Quick update.  It seems the problem with the PAL consoles is related to the F18A driving the CPU's interrupt.  I had problems with this initially while developing the F18A and the solution was a 100-ohm resistor between the FPGA and the interrupt output pin.  To prove or disprove this possibility, I modified my test F18A and removed the resistor (soldered a small jumper across the PCB pads where the resistor goes) and it seems to have fixed the problem.  Donkey Kong, which was failing before, works 100% now over ten or so tests (power-off, power-on, reset, re-insert the cartridge, etc.)  Just because I like having a resistor in there, I doubled two 100-ohm resistors on the PCB pads to make the equivalent of a 50-ohm resistor, and it also works just as reliably as the jumper.

 

I need to do more tests, but my multi-cart is acting up and I don't have any other carts to test with.  Is anyone else with a PAL CV (and having this problem) willing to make the mod to their F18A to test?  Not having the resistor in the circuit will not hurt anything, but you will need a decent soldering iron and such.

 

The resistor in question is R18 and is pretty accessible on the board.  A jumper across the pads, or a resistor between 1-ohm and 50-ohms should all work equally well.

Attached Thumbnails

  • f18a_r18_01.jpg
  • f18a_r18_02.jpg


#30 Mika73 OFFLINE  

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Posted Mon Mar 20, 2017 3:02 PM

It would be interesting try if River Raid and Space Fury work after this.


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#31 matthew180 OFFLINE  

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Posted Mon Mar 20, 2017 11:01 PM

This is not really a fix, just a test.  I originally added the 100-ohm resistor because without it the F18A could not drive the Z80's NMI input.  Now it seems ironic that removing it seems to help the problem with the PAL CV.  However, I still do not know why, and this modification is not 100%.

 

I do have another test that I am running where I am driving a standard TTL 74LS logic gate (an OR gate in this case) from the FPGA, then driving the interrupt output from the OR gate.  It looks like this:

 

FPGA ---> 74LS32 ---> Interrupt output.

 

This configuration works, and on the PAL CV I am testing with I have been able to run every game listed as not working, including River Raid, Gyruss, Donkey Kong, etc.  There are three problems with this fix:

 

1. Using 74LS logic is too big for the F18A (I'm looking for an SMD alternative that uses real TTL logic).

 

2. It would require a significant modification to existing F18A boards (although only those having problems would need to apply the fix).

 

3. I still do not understand why the existing F18A circuit does not work, so my fix is still just a hack and that bothers me.



#32 omf OFFLINE  

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Posted Fri Mar 24, 2017 2:58 PM

Quick update.  It seems the problem with the PAL consoles is related to the F18A driving the CPU's interrupt.  I had problems with this initially while developing the F18A and the solution was a 100-ohm resistor between the FPGA and the interrupt output pin.  To prove or disprove this possibility, I modified my test F18A and removed the resistor (soldered a small jumper across the PCB pads where the resistor goes) and it seems to have fixed the problem.  Donkey Kong, which was failing before, works 100% now over ten or so tests (power-off, power-on, reset, re-insert the cartridge, etc.)  Just because I like having a resistor in there, I doubled two 100-ohm resistors on the PCB pads to make the equivalent of a 50-ohm resistor, and it also works just as reliably as the jumper.

 

I need to do more tests, but my multi-cart is acting up and I don't have any other carts to test with.  Is anyone else with a PAL CV (and having this problem) willing to make the mod to their F18A to test?  Not having the resistor in the circuit will not hurt anything, but you will need a decent soldering iron and such.

 

The resistor in question is R18 and is pretty accessible on the board.  A jumper across the pads, or a resistor between 1-ohm and 50-ohms should all work equally well.

i dont mind giving this a go on mine with a jumper (wire) if that will help?

actually you probably don't even need to remove the resistor, just solder a wire on to each side, essentially turning it into a 0 ohm resistor as the easiest route will always be take which will be the wire. this would save removing the component






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