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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



#33 Mika73 OFFLINE  

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Posted Wed Mar 29, 2017 3:05 AM

Did you have time try jumper wire yet?


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#34 omf OFFLINE  

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Posted Thu Mar 30, 2017 1:01 AM

Did you have time try jumper wire yet?


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no not yet but i can make the effort maybe tonight, i have had various home DIY issues that needed my immediate attention rescently



#35 Mika73 OFFLINE  

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Posted Thu Apr 6, 2017 10:36 PM

Any news? :)


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#36 matthew180 OFFLINE  

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Posted Thu Apr 6, 2017 10:45 PM

I'm still working on it. I cannot get any consistency in my testing when I make changes or try different components.  Very frustrating.  I'm very certain the problem is the interrupt, but I cannot determine exactly how or why.



#37 Mika73 OFFLINE  

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Posted Fri Apr 7, 2017 2:30 PM

I was thinking that jumper wire. Does it fix problem and should I try that?


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#38 nanochess OFFLINE  

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Posted Sun Apr 9, 2017 9:51 PM

I'm still working on it. I cannot get any consistency in my testing when I make changes or try different components.  Very frustrating.  I'm very certain the problem is the interrupt, but I cannot determine exactly how or why.


I remember the Z80 is prone to errors if NMI isn't steady for some number of cycles. I would suggest pull up resistor to 5V+ and a decoupling capacitor to ground to trap "spikes".

#39 matthew180 OFFLINE  

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Posted Wed Apr 19, 2017 11:20 AM

@nanochess:  The main problem with adding components to the interrupt line is that I have no idea what computer the F18A is going into, and I can't possibly survey and accommodate every possible hardware situation.  I have to be electrically compatible with the original VDP, which in the case of the CV the interrupt line goes directly to the Z80's NMI via a single trace (as well as the expansion port pin).  I'm pretty sure the problem is not noise on the line, my o-scope tests show really clean interrupt signals.

 

Update: Do NOT modify your F18A as mentioned above as a possibility.  Some recent tests are pointing in a different direction.  I'll know more soon.



#40 Unstablewarpfield OFFLINE  

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Posted Fri Apr 28, 2017 11:20 AM

I'm jumping in here since I seem to have thesame issue, although I don't own that many games to test with. I also have a PAL unit with donkey kong not booting after the player choice, while other games (Smurph for example) work fantastic. Really blown away by the image quality btw Matthew. Running it through an internal vga-hdmi convertor on a large samsung lcd. Following this with interest. 


Edited by Unstablewarpfield, Fri Apr 28, 2017 11:25 AM.


#41 Mika73 OFFLINE  

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Posted Wed May 10, 2017 10:32 PM

Hope there will be some solution/fix get everything work ok. Use VGA wish video projector and Colecovision is great with big picture.


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#42 Unstablewarpfield OFFLINE  

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Posted Thu May 11, 2017 11:19 AM

Same here. I use an internal hdmi convertor and put it today on a 55" led screen in school for the kids I teach. Got an optional class going on called video game history :-)

Edited by Unstablewarpfield, Thu May 11, 2017 11:20 AM.


#43 matthew180 OFFLINE  

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Posted Mon May 15, 2017 12:27 AM

I'm still working on this.  I have a theory but it is going to take some effort just to test it.  I just wanted to post an update.



#44 Mika73 OFFLINE  

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Posted Wed May 17, 2017 10:58 AM

Thanks. Updates are always nice. Hope it's possible fix without sending boards back.


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#45 Mika73 OFFLINE  

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Posted Mon Jul 3, 2017 1:33 PM

Any news?


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#46 Mika73 OFFLINE  

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Posted Mon Aug 14, 2017 11:00 PM

Any news of Colecovision VGA problem?


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#47 Mika73 OFFLINE  

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Posted Thu Oct 26, 2017 9:14 AM

Is this problem forgotten? Haven't heard anything long long time.


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