Calling all Defender Repair Experts

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   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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Syrup2407 Members Profile Send Private Message Find Members Posts Add to Buddy List View Feedback Groupie Joined: 13 Dec 2014 Location: Cambridgeshire Status: Offline Points: 444 Feedback: 5	Post Options Post Reply Quote Syrup2407 Report Post Thanks(0) Quote Reply Topic: Calling all Defender Repair Experts 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

philmurr Members Profile Send Private Message Find Members Posts Add to Buddy List View Feedback Senior Members Joined: 13 Aug 2003 Location: Hampshire Status: Offline Points: 2433 Feedback: 5	Post Options Post Reply Quote philmurr Report Post Thanks(0) Quote Reply 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)

Syrup2407 Members Profile Send Private Message Find Members Posts Add to Buddy List View Feedback Groupie Joined: 13 Dec 2014 Location: Cambridgeshire Status: Offline Points: 444 Feedback: 5	Post Options Post Reply Quote Syrup2407 Report Post Thanks(0) Quote Reply 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