G7400 - screen is broken

Started by gehtjanx, August 18, 2023, 01:08:02 AM

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gehtjanx

Hello,
I had a working G7400 and when I now tried to use it, it has a strange "scrolling" image. It is _NOT_ the TV/RF, it is the actual console. The game also works fine on G7000.

Also note: Sound and keyboard is okay, but the image is not only looking bad, but actually has influence on the gameplay. What I mean: It does not only look bad, but e.g. in thie game (it is a maze) the player will go through walls or will make beep sounds even it I dont touch the controller, I am not moving, but the "walls" on the screen are so distorted that it registers it as if I moved into it.

I took out the ICs and put them back in after cleaning, but no real chang (or maybe even more distorted). When I let it fall, also no change.

HERE IS A VIDEO OF WHAT IT DOES:
https://youtu.be/nsfiHBugJTM

Is there any known fix or does anyone know what the problem is? I guess the IC is broken and I can throw it away now? This is the second broken G7400 that I saw (other one was already broken), it seems there is something very unreliable about this machine in particular.

I dont know, let me know if I can toss it because if the custom IC is bad, nobody can fix it anyway. Takes a lot of space and I am really angry about it now.

Thanks

Xuul

Hi,

could be IC651 (CPU) or IC652 ( object generator + sync generator ).
Do you have any replacement ICs so you could test which one is faulty?
Do you have the service manual with the nice troubleshooting guide?

Cheers

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

gehtjanx

Hello,

Thanks for your reply, I was assuming something custom died.

I only have a G7000, if that would help? Is that chips the same?

Thanks

Xuul

Nope, the G7400 CPU IC has a special G7400 only ROM, so IC651 MUST be the G7400 version.
Programmers don't die.
They just gosub without return.

gehtjanx

Hello again,

and that one: IC652
Can I try that one from a G7000 somehow?

Maybe worth a try?


And does anyone know why they die so often? I mean all the consoles are pretty sturdy and the G7400 seems to die so often, I guess Philips also made bad capacitors, has it something to do with that? This G7400 worked and I did nothing. I have the power switch IN all the time, I just plugged in the game, and then the power cord, and this happened, so it died while sitting around or by applying the power

Thanks

Xuul

IC652 should be interchangeable.

Do you have the service manuals? They contain an excellent trouble-shooting guide which guides you through replacing/checking the ICs step by step.

Well, the consoles are now about 40 years old. Almost all electrolytic capacitors inevitably dry out or leak sooner or later. Replacing them is never a mistake.
Another known problem with the G7400s is the disastrous solder joints on the power lines between the motherboard and the internal PSU. Not to mention the inferior power switches. I also had several failures with IC679 ( TEA1002 - PAL encoder chip ).

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

gehtjanx

Hello,

Thanks, I will maybe try but maybe give up on the G7400 it is cool but I cannot keep buying things that are breaking every time I use it.

I dont have any service manuals, usually the chips should have a print on them to see what is the same part or no.

In my experience, Philips has very bad capacitors. I had a broken VG 8000 PSU that only came on after some time, my G7200 also has a very tiny screen and it slowly gets bigger and bigger, etc.

I had a broken wire when i turned it around but that was not the main problem on this unit. I also noticed they use single contact sockets, not double wipe ones (the contact is only made on one side of the IC pin leg instead of squeezed on both sides). But all looked clean and it seems to me like something is faulty.

Thanks, hmm, I will maybe try to change the one IC you mentioned. Then, I have a broken G7000...

Xuul

The manuals are great for trouble-shooting. I use them all the time.
If you want them, send me your email via PM
Programmers don't die.
They just gosub without return.

gehtjanx

Are you sure I can swap this???

G7000
- has one 40 pin DIP chip
- says 8325

G7400
- has three 40 pin DIP chips
- says: 8332, 8341, 8342

NOT THE SAME NUMBER?

So which one can replace the 8325?

Thanks.

Xuul



This is from the service manuals.
IC652 has identical part numbers on both systems as you can see.
Also, there are logic and circuit schematics where you can see exactly which IC is which.
Repairs are so much easier with the manuals.
As I already said, PM me with an email and I'll send the PDFs

Xuul

(edit) link edited, should work now

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

gehtjanx

8045 seems to be a Intel CPU and seems to be the same.

I guess the numbers I posted are the DATE of production (week 32 / 41 / 42 of 1983)
THAT IS SO WEIRD that they do that. Usually, date code is on the bottom and not on the top. Usually it is
manufacturer, IC number
part number
date code

That is so strange, I never saw anything like that. Well, a Philips move ??? , I dont wonder why they went out of the computer and console business. Missing best practise, bad quality, strange construction with various versions (internal/external PSU, controllers etc), high production costs, etc., they just screwed in a modulator but all other companies integrated it on the board.

I cannot repair the IC itself, I can only take it from the other unit, dont think that it will help but maybe worth a try.

thanks.

Xuul

Quote from: gehtjanx on August 21, 2023, 10:39:07 PM8045 seems to be a Intel CPU and seems to be the same.
The CPU ( IC651 ) is basically the same IC on both systems but the G7400 version has a special ROM so you can't swap the G7000 IC651 with the G7400 IC651
Programmers don't die.
They just gosub without return.

Xuul

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

gehtjanx

Thanks, I was so concentrated on the big ICs, I swapped the one IC but made no difference. I also swapped the 2 RAM chips with each other, but also no difference.

I cannot repair it and there is no parts, so nothing that I can do.

I will sell it off as broken and be done with it.

Sad story, just a bad experience with G7400 altogether. It looks cool but 2 broken ones, no real advantage, if I used it for 10 minutes it would be a lot, I just tried it and then it died the next time I wanted to use it.

Thanks, but it is what it is, it's hard for me to wrap my head around, I tried my best but it is just a unit I cannot keep working no matter what I do or try or how many I buy or how much I invest, it just dies every time. I guess the other one (I received that already broken) had a similar problem.

Xuul

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