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Re: QL Video issue - Red color missing

Posted: Thu May 17, 2018 12:21 pm
by tofro
Your picture quality is incredibly good considering you are using the modulator.

Tobias

Re: QL Video issue - Red color missing

Posted: Sat May 19, 2018 1:11 pm
by 1024MAK
Protecting the 8301 ULA
Rather than just using 5.6V Zener diodes, adding some fast signal diodes can improve the protection. Use 1N4148 or similar. Connect a diode between 0V/GND and the signal pin, then another diode between the signal pin and the +5V power rail. Do this for all the signals that go to the RGB socket.

Code: Select all

       A  K             A  K
0V ----->|-------+------->|------- +5V
                 |
                 |
               Signal
               from
               ULA
               to
               RGB
               socket

You can of course retain the 5.6V Zener diodes.

The signal diodes will clamp any out of range voltage spikes within their current ratings.

Mark

Re: QL Video issue - Red color missing

Posted: Mon May 21, 2018 6:23 pm
by Quickie
Hi all,

Thanks again for all the provided information and suggested mods and improvements. This really increases my interest on the QL! :)
Unfortunately I am currently trying to fix a couple of Dragon32's and I would prefer repairing them before retaking on the QL (which I currently consider fixed, but misses the improvement) :)

Best regards!