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Author Topic: Videopac + G7400 not working, some help need.  (Read 4910 times)
Willy
Trying to get the cartridge in...
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Posts: 10


« on: March 03, 2013, 09:51:05 PM »

Hello.
I'm new here Smiley
Some days ago, I have bought a Videopac + G7400 as a bonus to another item. That was not tested, dirty etc.

First of all i've found that power switch is faulty. After 2 patient hours with tweezers finally it is working as (almost) new one.

So ... time to test. After few minutes I've tuned up the TV and got a partial picture, some pink lines on black background, or black on pink ... cant remember.
power off/wait/on ... and black screen ...  Cry

My question is, can somebody help me with repration? Maybe it is an common, known problem. I have necessary tools etc, but absolutelly no experience with those machines  Evil

Best Regards Willy.
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Seob
Give this man a Jopac!
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« Reply #1 on: March 03, 2013, 09:59:41 PM »

The power switch is a know problem. One of the members here has a work around using a different switch.
On the other problem i don't know. Is you're tv having problems tuning in on other older game systems like the atari 2600?
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8 bits of fun
Willy
Trying to get the cartridge in...
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Posts: 10


« Reply #2 on: March 03, 2013, 10:10:59 PM »

The switch has been disassembled, refurbished, and assembled again Smiley
 
There is no problem regarding TV, it is tune up well at channel 32.

I have stable picture with both syncs, but there is nothing on the sreen. Just stable black screen.
(maybe some very very little noise on black, but it can be noise from my other equipment.)
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gertk
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gertk64
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« Reply #3 on: March 04, 2013, 07:28:32 AM »

Obvious question: you did insert a cartridge in the G7400 ?
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>>G7000 G7200(P+S) G7400 N60 JET27 VG5000 ZX80 ZX81 ORIC-1 COMX35 Aquarius<<
Willy
Trying to get the cartridge in...
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Posts: 10


« Reply #4 on: March 04, 2013, 08:02:28 AM »

Yes.
I have also cleaned the cartridge slot.
I have oscillation on both cristals, All IC's are cold, only one is a bit warmer but no hot.
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Rene_G7400
Pedit5
I take the Videopac and leave the Canoli!
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« Reply #5 on: March 04, 2013, 09:17:02 AM »

Does the sound of the G7400 work? Do you hear the standard startup sound when you've inserted a cartridge and press RESET?
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Willy
Trying to get the cartridge in...
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Posts: 10


« Reply #6 on: March 04, 2013, 09:55:29 AM »

NO sound at all...
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Rene_G7400
Pedit5
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« Reply #7 on: March 04, 2013, 01:42:48 PM »

Do you have an oscilloscope and/or frequency counter?

Have you checked the circuit diagram of the G7400?
http://home.kpn.nl/rene_g7400/vp_info.html
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Willy
Trying to get the cartridge in...
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Posts: 10


« Reply #8 on: March 04, 2013, 05:11:43 PM »

Hi.
I have digital osciloskop, so I can manage that.

Thanks for the link. Tomorrow i'll try to look a bit deeper Smiley
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Seob
Give this man a Jopac!
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« Reply #9 on: March 04, 2013, 06:08:38 PM »

More info here: http://videopac.nl/forum/index.php?topic=1199.0
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8 bits of fun
Willy
Trying to get the cartridge in...
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Posts: 10


« Reply #10 on: March 05, 2013, 06:46:43 PM »

Hi.
It doesn't look good  Sad

There is almost no live on the CPU ...
I've found service manual, and checked some signals in connection to mode 3 no cart.

I can see only ALE signal and Clock.
All other lines are static ...
Additionaly pins 13 and 15 (B1 , B3) are changing state when I press reset. Does it means that CPU is dead ?

Regards
Willy.
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Rene_G7400
Pedit5
I take the Videopac and leave the Canoli!
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« Reply #11 on: March 06, 2013, 09:15:19 AM »

Does it means that CPU is dead ?

That is possible, I've seen that before in a G7400.

You could remove all other IC's that are connected to the 8048 and then check the 8048 again without cart. (remove IC's 8245, 6810, 8243 and EF9341.)

The only way to get a new 8048 is to get it from another G7400 (or program a 8748).
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Willy
Trying to get the cartridge in...
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Posts: 10


« Reply #12 on: March 06, 2013, 09:35:08 PM »

IC's removed ... no change
MPU is dead ...

I've ordered 8748.
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Rene_G7400
Pedit5
I take the Videopac and leave the Canoli!
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Posts: 2519



WWW
« Reply #13 on: March 07, 2013, 09:07:01 AM »

So you've got a programmer for the 8748?
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Willy
Trying to get the cartridge in...
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Posts: 10


« Reply #14 on: March 07, 2013, 10:43:44 AM »

Yes, I'am using Vellon vp-990
the 8748 is on the list.
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