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Author Topic: RGB for G7000  (Read 31534 times)
VideopacBelgium
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« on: June 16, 2009, 12:45:43 AM »

Hi!
Can we add a RGB output on the G7000 same as on the G7200 ?
Thanks.
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Rene_G7400
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« Reply #1 on: June 16, 2009, 09:43:26 AM »

Sure, if you make a PCB with the required components on it. (2 TTL IC's, a transistor and a couple of resistors and diodes.)
Only the 12V switch signal won't be available.
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VideopacBelgium
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« Reply #2 on: June 16, 2009, 05:42:06 PM »

Hi!
Thanks Ren?.
Yes I'm very interested for that.
Do you have the circuit diagram?
For the 12v switch, can I use a system with IC TL497 ? (VCC - VDD)
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Rene_G7400
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« Reply #3 on: June 17, 2009, 11:52:58 AM »

For the 12v switch, can I use a system with IC TL497 ? (VCC - VDD)

That should be possible (5V to 12V converter), but it might not be necessary if you just switch your TV to the external input manually.

Do you have the circuit diagram?

Not really.
Take a look at the circuit diagram of the G7200.
You'll need to add the following part numbers of this diagram to your G7000:

RGB:
IC653 (74LS08), IC652 (7407),
D692, D693, D694, D695, D696, D697 (6x 1N4148),
R746, R747, R748 (3x 1k5), R735, R736, R737 (3x 560E)

Audio:
R738 (470E), R751 (100E according to diagram, but 180E might be better)

Status RGB:
R723 (47E)

Sync:
TS681 (BC548B),
R733 (4k7), R772 (4k7), R773 (680E), R774 (180E)

This mod will be RGB only, no composite video.

http://home.kpn.nl/~mdr.vd.enden/download/g7200_2.jpg
« Last Edit: May 09, 2010, 10:31:14 PM by Rene_G7400 » Logged
VideopacBelgium
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« Reply #4 on: July 17, 2009, 01:13:46 AM »

Hi Rene,
I don't understand some connect:

IC 653: Pin 2,5,9,12 must be connected to which point?

Connections IC 653 and IC 652:
IC 653 pin 11 (L) to connect to IC 652 pin 11 + pin 9 + pin 13 ?
IC 653 pin 3 (G) to connect to IC 652 pin 1 ?
IC 653 pin 6 (B) to connect to IC 652 pin 5 ?
IC 653 pin 8 (R) to connect to IC 652 pin 3 ?

Thanks.
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Rene_G7400
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« Reply #5 on: July 17, 2009, 12:32:18 PM »

IC 653: Pin 2,5,9,12 must be connected to which point?

That's the blanking signal. It should be connected to pin 39 of the 8048 (or pin 8 of IC 670), but you'll need an inverter like on the schematic of the G7200.

Connections IC 653 and IC 652:
IC 653 pin 11 (L) to connect to IC 652 pin 11 + pin 9 + pin 13 ?
IC 653 pin 3 (G) to connect to IC 652 pin 1 ?
IC 653 pin 6 (B) to connect to IC 652 pin 5 ?
IC 653 pin 8 (R) to connect to IC 652 pin 3 ?

Yes, that's correct.
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VideopacBelgium
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« Reply #6 on: July 21, 2009, 01:41:19 AM »

Oops! the RGB PCB works but the screen scrolls from left to right...
Problem with the inverter 74LS04?



« Last Edit: July 21, 2009, 11:50:10 AM by VIDEOPAKBELGIUM » Logged

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Rene_G7400
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« Reply #7 on: July 21, 2009, 12:31:55 PM »

Looks more like a problem with the Sync signal (the transistor circuit).
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Seob
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« Reply #8 on: July 21, 2009, 06:11:04 PM »

nice clear font.
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VideopacBelgium
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« Reply #9 on: July 21, 2009, 06:45:57 PM »

Looks more like a problem with the Sync signal (the transistor circuit).

I re-checked the transistor circuit, it seems to me this is ok.
On the G7200 diagram, R733 (4k7) was connected to the pin 6 of the IC 656.
However on my RGB PCB, the resistor 4K7 was connected to the pin 11 of the IC 669 = P.6.6  (composite video) of the G7000. Is this correct?
Thanks.
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Rene_G7400
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« Reply #10 on: July 21, 2009, 11:02:24 PM »

On the G7200 diagram, R733 (4k7) was connected to the pin 6 of the IC 656.
However on my RGB PCB, the resistor 4K7 was connected to the pin 11 of the IC 669 = P.6.6  (composite video) of the G7000. Is this correct?

That should be the same signal.

Maybe a silly question, but: have you switched your TV to the external input? I've seen this problem before on older TV's with an RGB input. The SCART connector has two switch signals, one for switching the TV to the external input (pin 8, 12V), and one to switch from composite video to RGB (pin 16, 2V). Because the G7000 doesn't have a 12V power supply, you probably haven't connected the signal for pin 8 of the SCART connector, but you have connected the signal for pin 16. The result is that the TV does switch to the RGB input, but not to the external input. As the Sync signal goes through the external input, you will see the RGB signal, but without sync.
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Seob
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« Reply #11 on: July 23, 2009, 06:30:28 PM »

@Videopakbelgium

Can you draw a circuit diagram of your pcb? I don't understand the diagram rene has put on the net. I want to build one as well.
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VideopacBelgium
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« Reply #12 on: July 24, 2009, 02:07:32 AM »

On the G7200 diagram, R733 (4k7) was connected to the pin 6 of the IC 656.
However on my RGB PCB, the resistor 4K7 was connected to the pin 11 of the IC 669 = P.6.6  (composite video) of the G7000. Is this correct?

That should be the same signal.

Maybe a silly question, but: have you switched your TV to the external input? I've seen this problem before on older TV's with an RGB input. The SCART connector has two switch signals, one for switching the TV to the external input (pin 8, 12V), and one to switch from composite video to RGB (pin 16, 2V). Because the G7000 doesn't have a 12V power supply, you probably haven't connected the signal for pin 8 of the SCART connector, but you have connected the signal for pin 16. The result is that the TV does switch to the RGB input, but not to the external input. As the Sync signal goes through the external input, you will see the RGB signal, but without sync.

I re-checked again and again ...
Finally, I find 12v on the G7000. I connect pin 8 (scart) through 1k resistor + 1N4148 to the pin 11v from the external power supply. The TV switches to RVB when I turn on the G7000 such as the G7400 .... but this is the same screen which roll and roll and roll from left to right .....
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Rene_G7400
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« Reply #13 on: July 24, 2009, 09:13:03 PM »

I think I've found the problem: there's an error in the circuit diagram of the G7200! For IC 656 they've used a NAND symbol, but in reality it is an AND gate! So if you connect the input of a free inverter to pin 11 of IC 669 of your G7000, and the output of the inverter to your transistor circuit (4k7 resistor), it should work.
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VideopacBelgium
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« Reply #14 on: July 24, 2009, 11:26:50 PM »

?::: P:::? ?:::E:::? ?:::R:::? ?:::F:::? ?:::E:::? ?:::C:::? ?:::T:::?

Thanks Ren?, it works !!!


Marvellous sharp screen with RGB mod !

Sync signal from pin 11 IC 669 to the inverter IC 74LS04

12v on G7000 from ext. power supply
« Last Edit: July 24, 2009, 11:43:45 PM by VIDEOPAKBELGIUM » Logged

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