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Calling all Defender Repair Experts

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Syrup2407 View Drop Down
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    Posted: 12 Oct 2017 at 8:12pm
Hi all,

I have a Defender that has developed a really odd fault.

When the game is started the rug pattern will be displayed (and looks correct) and the message 'Initial Tests OK' is displayed, but then the game enters the service mode where the mode will automatically increment up to 28 and then boot back to the rug screen. The selected mode increases very rapidly it reaches 30 in about 2 seconds. Pressing any of the switches inside the door has no effect on this.

I have tested all of the RAM chips (in an old ZX Spectrum) and have tested the ROMS and these are all OK.

Has anyone seen anything similar or any ideas where I should start looking?

Many thanks,

Gav
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philmurr View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote philmurr Quote  Post ReplyReply Direct Link To This Post Posted: 12 Oct 2017 at 8:36pm
I’d suspect the PIA on the ROM board.

You might want to first check the inverter that buffers the inputs from the coin door (and feeds the PIA)
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Syrup2407 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Syrup2407 Quote  Post ReplyReply Direct Link To This Post Posted: 12 Oct 2017 at 8:40pm
Hi Phil.

Thanks for the pointers.

I will try to take a look with the oscilloscope at the weekend.

Cheers,

Gav

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