Videopac 7400 strange things

Started by Turbosoni, June 29, 2023, 04:53:32 PM

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Turbosoni

Hi everyone from Spain, I'm a retro fan and I got a 7400 that doesn't work, the console didn't connect for 20 years, when you put in a game it shows a black screen, sometimes the select Game thing comes out but it sort of disappears little by little and when you select a game weird glitches appear and in most cases black or grey screen

The console has the power switch hooked but it always stays on, I don't know if that could be the fault that the correct current does not reach it.

It seems that if I move the game it wants to start but it doesn't come, on the second or third attempt without moving this no longer appears, but a black screen. The select Game thing is supposed to stay fixed and it doesn't go away as is my case. From what I thought, it may be something related to the slot or the pins, but I have cleaned both the slot and the games and this continues to happen.

Do you see them too far apart?

Failure video:
[embed]https://youtu.be/Wb9rydxuIRI[/embed]

Pins:

Xuul

Hey,

strange behavior. The power switch is not the problem causing the malfunction.
Wipe the contacts of the game cartridge with a Q-tip soaked in 99.9% Isopropanol and insert and remove the cartridge several times. Soak the Q-tip again and repeat the process at least 3 times.
If it still does not work, open the console and replace IC651, IC652, IC661 and IC662.
IC651 is the C.P.U., the rest are for video/GFX.
These are all socketed ICs and easy to replace. You just need a different videopac for it. Or you could try eBay for the ICs.

Xuul

Programmers don't die.
They just gosub without return.

Turbosoni

Quote from: Xuul on July 17, 2023, 12:24:44 AMHey,

strange behavior. The power switch is not the problem causing the malfunction.
Wipe the contacts of the game cartridge with a Q-tip soaked in 99.9% Isopropanol and insert and remove the cartridge several times. Soak the Q-tip again and repeat the process at least 3 times.
If it still does not work, open the console and replace IC651, IC652, IC661 and IC662.
IC651 is the C.P.U., the rest are for video/GFX.
These are all socketed ICs and easy to replace. You just need a different videopac for it. Or you could try eBay for the ICs.

Xuul



It can't be the separate pins? I've got a working videopac 7000 and the pins are closer together. Is a damaged 7000 used to make the change of the chips or does it have to be a 7400? Thanks

Xuul

The pins look ok to me.
I fixed a G7000 a while ago that had a broken pin ( one half of one of the separated pins had broken off ). I had to put a toothpick behind the remaining pin, so there was enough pressure to push the pin against the cartridge when it was inserted. Worked like a charm.

I re-read your original post. How exactly is the power switch "hooked"? Is it just stuck by itself?
To really make sure that the problem is not caused by the power switch, you should bypass the power switch first.

Most ICs ( I think ) can be swapped between 7000 and 7400, others cannot. You should use a spare G7400 if you want to swap ICs. You definitely can't swap the CPU because it contains a special G7400 only ROM.

P.S. If you PM me your email, I can send you a service manual PDF for the G7400 with an excellent step-by-step trouble-shooting guide, circuit diagrams and IC listings.
Programmers don't die.
They just gosub without return.