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Author Topic: G7000 Modding: noisy Power Supply, RGB and 60Hz Video-Output  (Read 2122 times)
ArcadeTV
Trying to get the cartridge in...
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Posts: 16



« on: December 19, 2013, 04:14:37 PM »

I just entered the Videopac-Scene and got myself a G7000 to relive some childhood memories.
The system I have seems to be in great shape. I already ordered an RGB-DAC-PCB and I'm looking forward to do some modding.

One thing I noticed right away is that the power supply is singing, to be precise it produces a very high pitched, squeeking sound.
Is there a common cure for this or is it just normal that such an old PSU is noisy?

I was wondering if there is a way to output a 60Hz video-signal from a pal-machine...
I've been doing console-mods for a long time now, but I never worked on a videopac. There are some systems like the Mega Drive, Jaguar or Neo Geo that can be changed to 60Hz by just setting a bridge to a jumper-connection... Others like the NES need a CPU and crystal from an NTSC-donor-console....
Would be an awesome thing if the videopac could be set to PAL-60 so that the screen is completely filled vertically without the typical 50Hz-letterbox-borders.

Any info on this is very much appreciated, thanks guys and a merry xmas to all of you!
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Define
Attacked the Timelord
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Posts: 125



« Reply #1 on: December 19, 2013, 04:50:18 PM »

Welcome!

I think a capacitor on your system's adapter is a bit near the end but yet still working...?
They don't make a high pitched noise as i am aware of in my 7000, 7200 and 7400 system.

I am not aware of a 60Hz mod, maybe somebody here knows more but i am keeping my systems stock.
I do have 2x7000 and soon another 7400 but i will sell them off maybe, don't have to have doubles.

Nice days to you too from Holland  Smiley



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Videopac 4 life
ArcadeTV
Trying to get the cartridge in...
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Posts: 16



« Reply #2 on: December 19, 2013, 04:59:11 PM »

Thanks!
I didn't open the system yet, but if the caps look fishy I will surely get a cap-kit and replace those thingies..

As for the 60Hz-output, I'm afraid I found that this will not be possible by only tweaking a simple internal connection...
http://soeren.informationstheater.de/g7000/palntsc.html
There are too many different clockspeeds, so for 60Hz I will likely end up with buying a beat-up Odyssey2 and mod those internals into my G7000 along with the RGB-stuff....

But maybe someone here knows more about that...
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Define
Attacked the Timelord
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Posts: 125



« Reply #3 on: December 19, 2013, 05:03:45 PM »

Replacement of the (maybe) defected cap will be a lot easier i think  Wink
Some 7400's do have RGB outputs and a 7200 has that too (DIN like to Scart adapter needed)

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Videopac 4 life
Rene_G7400
Pedit5
I take the Videopac and leave the Canoli!
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« Reply #4 on: December 20, 2013, 09:43:30 AM »

If the main thing you want is to remove the letterbox borders, then you don't need to make it 60Hz, you could adjust the vertical blanking signal. However some games change the background color directly after the Vsync interrupt (which happens before the actual Vsync pulse), so this color change will then be visible at the bottom of the screen. (I've made a switch on my G7400 to change the blanking signal.)
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ArcadeTV
Trying to get the cartridge in...
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Posts: 16



« Reply #5 on: December 20, 2013, 11:40:46 AM »

René, that sounds interesting. Could you explain how to do that?
So I guess changing some ICs and clocks to accomplish a 60Hz-Mode is not possible?

A heart-felt THANK YOU!
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Rene_G7400
Pedit5
I take the Videopac and leave the Canoli!
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Posts: 2519



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« Reply #6 on: December 20, 2013, 09:56:30 PM »

René, that sounds interesting. Could you explain how to do that?
So I guess changing some ICs and clocks to accomplish a 60Hz-Mode is not possible?

Trying to make a 60Hz mode on a Videopac console is not a good idea. I know Soeren Gust has tried it, but he had problems to get a picture with color (instead of black-and-white only). And PAL-only games won't work anymore. Making an RGB output on an Odyssey2 console would be a better idea if you want a 60Hz console.

I've tried the blanking adjustment only on a G7400 console. It will only affect games without Plus graphics (pin B of the cartridge connected to ground), because the Plus graphics are limited to 320x250 pixels, so will always have black borders.

To minimize the vertical blanking, do the following:
- interrupt the signal that goes to pin 15 of IC680 (74LS157)
- combine the signals from pin 12 (M/S) and pin 10 (TL/64) of IC664 (74LS393) in a NOR gate (74LS02)
- combine the output of the NOR gate and pin 7 of IC652 (8245) (HBL) in a second  NOR gate, and connect the output to a third NOR gate to invert it (or use an OR gate instead of 2 NOR gates)
- connect the output of the inverter (NOR) to pin 15 of IC680.

It would be best to connect pin 15 of IC680 to the output of a switch, so you can choose between the original blanking signal and the new blanking signal.

This should work on a G7000 too, but then use pin 9 of IC679 (PAL encoder) instead of pin 15 of IC680.
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