Dragon 32 RGB SECAM and video tests

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Azerpy
Posts: 39
Joined: Tue Apr 09, 2019 1:16 pm
Location: France Pyrenées

Re: Dragon 32 RGB SECAM and video tests

Post by Azerpy »

Hello Mike
Thank you for your interest and care for all those things about the Dragons.
Yes you are right, I wrote on 27 july "The good input of luma is not exactly the output Y of the VDG ...
For his RGB converter, Retrocant must pick up into the PAL machines and adapt with a transistor or other way a signal similar with the one I named "LUM" present on my RGB SECAM Dragons pin 7 of PL6 and pin 7 of PL10 (see first schematic on this topic).
By me, it's somewhere after the output of IC 4053 multiplexor. On my RGB SECAM Dragons, the logic circuitry before the multiplexor is quite the same as on PAL schematics of D32 and D64.
retrocant
Posts: 12
Joined: Sat Jul 24, 2021 2:02 pm

Re: Dragon 32 RGB SECAM and video tests

Post by retrocant »

Greetings, I return to the thread attaching more information about the @azerpy project, beta version 1.0 Dragon-RGB board.
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Captura de pantalla 2022-02-14 a las 20.27.29.png
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Azerpy
Posts: 39
Joined: Tue Apr 09, 2019 1:16 pm
Location: France Pyrenées

Re: Dragon 32 RGB SECAM and video tests

Post by Azerpy »

Hello Alfredo
Glad to see you here again. I like your project and can help you go to the end.
(I want to say again that I not the designer of the RGB schematic. I have only understood, reproduced and shared what exists on the PSU Board of my Dragon SECAM RGB).
I now have got a PAL Dragon and could test with success my RGB board on it. For the luminance signal, you only have to pick it up on the motherboard.
On the Dragon 64 and some Dragon 32 motherboards, the video is amplified with 3 transistors. The signal pin 14 of IC11 before the resistor of 1K2 ohms (R58 / Dragon 64 or R6 / Dragon 32 ) is correct.
For other Dragons that have an operational amplifier, that signal has a negative DC offset, not impossible but needs adaptation.
You will need variable resistors of 500 ohms to adjust brightness and colors on the outputs R, G and B.
Ready for the prototype ?
retrocant
Posts: 12
Joined: Sat Jul 24, 2021 2:02 pm

Re: Dragon 32 RGB SECAM and video tests

Post by retrocant »

Greetings azerpy, I'm sorry it took so long to make the pcb, due to work and other issues I haven't been able to continue with the project, right now I've ordered beta1.0 version boards.

thanks for the information in what you comment on the PAL version, to add variable resistors of 500 ohms, which will have to be integrated into the board, even also in improving the regular linear that I have put 7905 to be able to get -5volts temporarily in Dragon64. Little by little we are going to make the necessary adjustments to know if the PCB that I have is correct and how you comment on the modifications that must be made.

I keep informed.

PS: I have signed the pcb to integrate you in the project, I have based myself on your scheme and I have decided to include you.
Azerpy
Posts: 39
Joined: Tue Apr 09, 2019 1:16 pm
Location: France Pyrenées

Re: Dragon 32 RGB SECAM and video tests

Post by Azerpy »

Don't be sorry, all that's only for fun !
retrocant
Posts: 12
Joined: Sat Jul 24, 2021 2:02 pm

Re: Dragon 32 RGB SECAM and video tests

Post by retrocant »

I have already received the PCB version beta 1.0
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unumlapis
Posts: 102
Joined: Sat May 04, 2019 11:29 pm
Location: Malmo, Sweden

Re: Dragon 32 RGB SECAM and video tests

Post by unumlapis »

Any pictures from output tests with this board that can be shared? Curious to see how it looks. :)
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