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Calling all Defender Repair Experts

Printed From: ukVac.com
Category: Technical
Forum Name: Tech, Maintenance & Repairs
Forum Description: Need Help? Ask Here
URL: http://www.ukvac.com/forum/forum_posts.asp?TID=360349
Printed Date: 18 Dec 2017 at 2:49pm


Topic: Calling all Defender Repair Experts
Posted By: Syrup2407
Subject: Calling all Defender Repair Experts
Date 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



Replies:
Posted By: philmurr
Date 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)


Posted By: Syrup2407
Date 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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