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Author Topic: Mod for the European G7000 to an A/V (Composite or FBAS output)  (Read 28799 times)
grgh
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george.r.g.hayward
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« on: May 17, 2008, 11:19:19 AM »

I've received a question, can anyone help me with:
Is there a mod for the European G7000 to an A/V (Composite or FBAS output)?
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Rene_G7400
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« Reply #1 on: May 17, 2008, 09:41:41 PM »

Is there a mod for the European G7000 to an A/V (Composite or FBAS output)?

Of course it is possible, but:

- the 1-transistor method I use for the Odyssey2 and G7400 does work for the G7000 too, but not very well, since the video-output level of the G7000 is too low, which will result in a darker picture.
- I've used a 2-transistor video-buffer with frequency compensation which does produce the correct video output level, but it is less easy to build, and looks messy inside the console or requires a small extra PCB.

It would be better to mod a G7400, which is easier and results in a better picture.
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Seob
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« Reply #2 on: June 24, 2008, 08:01:15 PM »

Rene do you have a schematic of the g7000 2 transistor hack? Or some pictures?
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Rene_G7400
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« Reply #3 on: June 24, 2008, 11:52:05 PM »

Rene do you have a schematic of the g7000 2 transistor hack? Or some pictures?

Not at the moment.
I've used a standard video amplifier circuit consisting of two CE stages, the first stage with an NPN transistor, followed by a stage with a DC coupled PNP transistor, and adjustable feedback from the second collector to the first emitter.
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Rene_G7400
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« Reply #4 on: June 25, 2008, 10:51:25 PM »

I've checked the circuit again, it sounded more complicated then it actually is. Apparently I had already reduced the number of components. This is the circuit:

« Last Edit: November 29, 2009, 04:00:54 PM by Rene_G7400 » Logged
Plink
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« Reply #5 on: August 07, 2008, 01:02:20 PM »

Hello guys,

i'm new to the videopac scene.
Recently got a G7000 European (made in France)....

I can't get a clear signal through the RF connection.

Is there any EASY (like the G7400) mod? or any way to make the RF signal clear?

I'm totally confused with all the mods that require 1 or 2 transistors...i can only do simple electronics...not very comfortable with making a whole circuit...

btw...what are the four cables that go to the RF box? can I do something with them?
is there a way to maybe find and install a new RF box?

 
thanks in advance for any answers...

 
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grgh
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george.r.g.hayward
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« Reply #6 on: August 07, 2008, 02:28:35 PM »

Howdy Plink & welcome,
Where is the world are you? Do you know if your TV is PAL/SECAM/NTSC?
Where exactly did the G7000 originate from?
Does this mean you do get a signal, but its just not clear?
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Plink
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« Reply #7 on: August 07, 2008, 02:36:12 PM »

I live in Greece and my TV has settings for Pal/Pal1/SECAM ...
the videopac i bought it from England through ebay...but it is made in France (dunno if it makes any difference.

I can get an RF signal, but its not clear.
I opened the console and tried to play with the "trimmers" inside the rf modulator, but I couldnt clear out the picture.

Thus, i'm looking into other solutions.
Like the av mod.

I have now opened the console and have the pcb on my hands...I also removed the 1 of 2 silver shielding boxes it had.
And as far as I understand there is the PAL encoder thing and the respective points that I've seen in the simple odyssey 2 mod
Audio output = junction of C45 and R49
Video output = junction of C44 and R7
But on my videopac the reference numbers are not the same.
The 2 capacitors have the numbers 7875 and 7854 and the Resistances are 7766 and 7743

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Sweersa
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« Reply #8 on: August 07, 2008, 02:52:17 PM »

I have an odyssey 2 with a worse than normal RF connection, even when I swap the RF modulator with a known normal/good RF box from a good O2 the picture is still iffy on that one particular console.  I am hoping the AV Mod will correct that.
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Plink
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« Reply #9 on: August 07, 2008, 03:04:03 PM »

Can't I use the cables that connect the RF modulator with the motherboard to connect av ports?

This is how my motherboard looks like....can anyone tell where I should solder the RCA jacks in order to get one video out and one audio out?



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Rene_G7400
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« Reply #10 on: August 07, 2008, 03:18:41 PM »

I can't get a clear signal through the RF connection.

So you DO get a recognizable Videopac signal, but it just has a lot of noise/snow.... ?

Is there any EASY (like the G7400) mod? or any way to make the RF signal clear?
btw...what are the four cables that go to the RF box? can I do something with them?

There might be something wrong with the RF cable or connector. Adjusting the trimmers of the RF box is definitely NOT a good idea (even the service manual says never to re-adjust them).

The 4 wires that go the the RF box are:
+5Volt, GND, audio, composite video.

The composite video signal which goes into the RF box is too weak to be sent to the video input of a TV directly, that's why you need 2 transistors.
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Plink
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« Reply #11 on: August 07, 2008, 03:26:41 PM »


So you DO get a recognizable Videopac signal, but it just has a lot of noise/snow.... ?

Exactly

There might be something wrong with the RF cable or connector. Adjusting the trimmers of the RF box is definitely NOT a good idea (even the service manual says never to re-adjust them).

The 4 wires that go the the RF box are:
+5Volt, GND, audio, composite video.

The composite video signal which goes into the RF box is too weak to be sent to the video input of a TV directly, that's why you need 2 transistors.

So in theory I can connect rca jacks on the audio and composite video cables and I will have - weak - signal?
And if I put the transistors inbetween the cable and the video jack I will get the proper strong signal?

Do you know which color cables are audio and composite?

There are orange (it is ground Icheckes) red, brown and black.


The transistors needed are special hard-to-find parts?
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Rene_G7400
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« Reply #12 on: August 07, 2008, 04:54:35 PM »

So in theory I can connect rca jacks on the audio and composite video cables and I will have - weak - signal?

The signal might be so weak that your TV won't recognise it. If it does, the picture will be very dark.

And if I put the transistors inbetween the cable and the video jack I will get the proper strong signal?

Correct.

Do you know which color cables are audio and composite?
There are orange (it is ground Icheckes) red, brown and black.

I will check that.

The transistors needed are special hard-to-find parts?

No, you can use any general purpose transistor (low power, silicium), the only thing you have to take notice of is that you need one PNP transistor and one NPN transistor.
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Plink
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« Reply #13 on: August 07, 2008, 05:02:46 PM »



No, you can use any general purpose transistor (low power, silicium), the only thing you have to take notice of is that you need one PNP transistor and one NPN transistor.


Thanks for all the help!!!

I'll try go today at a store with electronic parts and ask for two transistors one PNP and the other NPN.
Do i need anything else to buy for the mod? and resistances or some capacitors?


As for the cables, i dunno if it helps but this is how my rf modulator looks like


The orange is ground, but I can't figure out the others.
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Rene_G7400
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« Reply #14 on: August 07, 2008, 06:18:34 PM »

I'll try go today at a store with electronic parts and ask for two transistors one PNP and the other NPN.
Do i need anything else to buy for the mod? and resistances or some capacitors?

Check the schematic in the other post: you need two resistors (220 and 680 ohm) and one variable resistor (1k).
The capacitor does improve the signal, but it will probably work without it too.
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