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Author Topic: Defender Cocktail problems  (Read 1058 times)

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Jszekeres

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Defender Cocktail problems
« on: October 18, 2019, 10:12:13 am »
I recently acquired a Defender Cocktail arcade.  Right now I am having 2 issues.  It was working fine but this problem happened yesterday.   When I start a 1 player game, the screen is flipped the wrong way and the controls are working for player one.  If I start a 2 player game player one is flipped wrong  and player 2 is fine and the controls do switch sides on the game correctly.   So it seems something is causing my game display to be stuck on player two.  The theory manual says the screen control is what does this flipping.  However I do not know where to start looking on the PCB. 

The second problem is when I power on the game I get vertical lines on the screen. Then if I remove and reinstall the connector IJ3 a couple of times it then boots up correctly.  I saw that someone posted this exact same problem 6 years ago and nobody answered his post. The game does have a newer power supply that looks like it was pulled out of an old computer maybe.  The voltages on it seem ok.   

I will attach a screen grab of the old post with my problem.

Anyway any help would be much appreciated. 

Thank you.  Joe

Jszekeres

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Re: Defender Cocktail problems
« Reply #1 on: October 18, 2019, 04:04:39 pm »
I have solved both problems.  I looked at the schematic and it showed the SCREEN CONTROL line.  Since I knew this was where the problem probably was based on the Theory manual I began to check some levels.
The screen control was coming from the IC 5B as labeled on the schematic.  This IC is a 7404, Hex Inverter.  The input for the Screen Control is pin 9 and it was HIGH.  The output was at 1.88vdc .  Seems to be floating.  I grounded the output pin (8) and the video screen on the game flipped.   I also tested the input pin 9 in a 2 player game.  on player 1, it would go HIGH and on player 2 it would go low.  So this is the signal that tells the circuits to flip the screen.    Anyway I replaced 5B and it fixed the problem.  It also fixed my other problem as well as a third problem.

Anyway, I hope this helps someone someday.

Thanks

Joe    :burgerking: