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Author Topic: Philips G7400 video problem  (Read 126 times)
Macross_VF1
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« on: August 09, 2019, 09:20:51 PM »

So I have an issue with my Philips Videopac G7400. It outputs a piss poor RF signal, no matter how much I try to tune the TV. When I started digging around the net I saw that it was easy to convert to RGB, just a matter of installing a number of components.

https://www.the-nextlevel.com/odyssey2/articles/g7400guide/rgbmod.php

Unfortunately, nothing improved. As can be seen in the attached image (the image was taken while using RGB), the signal is still distorted and it does not matter if it is RF, composite or RGB. Anyone have any idea what the problem might be? I have tested the internal AC adapter and it outputs pretty much the correct voltage, 4.95V on one line and 11.43V (should be 5 and 12V respectively) on another.

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Macross_VF1
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Posts: 6


« Reply #1 on: August 10, 2019, 12:47:24 PM »

No matter, it's dead now. I tried reseating the socketed chips and I must have damaged at least one because it only shows a black screen. FML
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VideopacBelgium
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« Reply #2 on: August 10, 2019, 02:04:11 PM »

Hi !
Which piece / component have you damaged?
I have a lot of spare component.

Regarding the screen, it seems like a bad synchro.

 Cool Cool Regarding the screen closer, it's not the synchro.
I've the same screen before and it was 940 and 941 chips.
« Last Edit: August 10, 2019, 05:11:19 PM by VideopacBelgium » Logged

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Macross_VF1
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Posts: 6


« Reply #3 on: August 10, 2019, 02:44:15 PM »

That's the problem. I don't which, if any, part I might have damaged. Considering there are several socketed chips (10 I think), that would mean a lot of testing just to get right one. If I owned another G7400 it would have been much easier but since I don't I can't do much.

As for the video problem, I first thought of the sync as well, so I rigged a simple circuit and took Csync directly from the point where Hsync and Vsync are mixed into Csync but that didn't help at all.
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VideopacBelgium
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« Reply #4 on: August 10, 2019, 03:53:03 PM »

The better way is to find (or buy) a complete working french mainboard.
The french G7400 has factory RGB output (but not video output, only sync.)
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Macross_VF1
Trying to get the cartridge in...
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Posts: 6


« Reply #5 on: August 11, 2019, 02:01:34 PM »

It's alive again! Granted, the bad picture is still there, but it's an improvement. Turns out, the chips in the sockets really didn't want to connect unless I bent the legs in underneath the chips slightly. I suppose I shouldn't be surprise, the sockets are single wipe only and oxidized as well. So! Back to figuring out what can be done.

Cool Cool Regarding the screen closer, it's not the synchro.
I've the same screen before and it was 940 and 941 chips.

Which chips are those and where can I get some replacements?
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VideopacBelgium
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« Reply #6 on: August 11, 2019, 06:51:51 PM »

IC661 : EF9340
IC662 : EF9341
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Macross_VF1
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« Reply #7 on: August 11, 2019, 10:05:09 PM »

I suspected as much but I wanted to be certain.

I've been searching around a bit and these chips are not easy to find. There are some on ebay, but the cost is a bit high for the 9341 chip. Damn ebay prices.
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VideopacBelgium
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« Reply #8 on: August 14, 2019, 02:03:10 PM »

I suspected as much but I wanted to be certain.

I've been searching around a bit and these chips are not easy to find. There are some on ebay, but the cost is a bit high for the 9341 chip. Damn ebay prices.

Hi! I have a few spare chips EF9340 & EF9341 for the G7400.
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Macross_VF1
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Posts: 6


« Reply #9 on: August 15, 2019, 10:53:21 PM »

Spare chips you say? Well I'm certainly interested. Better than paying the Ebay scalpers at the very least.
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