I'am new in this forum and also in console restoration.
My first machine was an Amstrad CPC 6128 and I am try ot restore a GX400 (a flagship console :o ) to play again to my favorite games.
The GX4000 I bought (a french model) had problems with DB9 ports (missing pins). I was able to unsolder them and change them with DB9 ports from an English version of GX4000.
After the changes last night late, I was able to test the console which worked perfectly (We still had 1 time 1 red screen with horizontal black bars)
Stable image, perfect sound and the children even tested it.
But this morning ... : sound, but no image.
The TV detects a source but the screen remains definitively black
The game (burning rubber) starts correctly and the joysticks respond (I can start the game, accelerate and hear my racing car).
What I tested:
- clean the cartridge port and the cartridge
- try another copy of burning rubber
- change SCART cable
- change for a SCART cable to RGB (and therefore change the source at the TV)
- the memories are not hot and therefore a priori not faulty.
My diagnosis.
- Z80 and asics work, otherwise games would not start
- The food is correct, same reason as above
- memories had to be ok for the same reason
What I did not do: I did not make the wrong entry for the power supply -> I obstructed the 5V port with a plug from the English GX4000.
If you see points to test, I am interested. I can test with an oscilloscope and a voltmeter.
Sorry for the english ...
Best regards
Hello again
I am self-editing after some additional tests.
I tested the outputs directly at the scart.
I find a signal at 50 Mhz signal which seems normal.
I tested the DAC (IC15) which also seems to give me a signal on pins 15 to 17.
I'am stuck :'(
Thanks for your help
Try a din 8-> scart cable with a 5v power supply. Then you jump all the scart conversion zone and can check if the problem is in the asic or in the scart zone.
Hi
Thanks for your reply !
I have 2 questions to do the right test :
- I have a din 8 -> scart cable coming from another console (a twin famicom). Is it ok ? or should I have a specific Din 8 ? In my understanding all cable in Din8 should be good but I prefer to validate with you.
- Could I power the console with the 11v power supply (in the appropriate hole of course) instead of the 5V? When I see the PCB in the Service Manual schema I understand that for french version the 11v is also used to power the 5v circuit (but As I'am beginning I'am probably wrong .. but I try ;) )
Thanks for your help
Yo need the plus computer scart cable.
http://www.cpcwiki.eu/index.php/TV_SCART_cable
The 5v is the plug used to connect it with the din 8 cable. The diference is it not power the scart and rf part.
It should be o.k with 11v in the apropiate connector.
DO NOT plug in 11v to the 5v socket otherwise you'll have a nice doorstop!!!!
Quote from: freenutella on 21:23, 02 June 20
Hi
Thanks for your reply !
I have 2 questions to do the right test :
- I have a din 8 -> scart cable coming from another console (a twin famicom). Is it ok ? or should I have a specific Din 8 ? In my understanding all cable in Din8 should be good but I prefer to validate with you.
- Could I power the console with the 11v power supply (in the appropriate hole of course) instead of the 5V? When I see the PCB in the Service Manual schema I understand that for french version the 11v is also used to power the 5v circuit (but As I'am beginning I'am probably wrong .. but I try ;) )
Thanks for your help
The Twin Famicon uses the same physical connector, but the pinout is completely different. It definitely won't work on the GX4000. In fact it may even damage either the TV or the GX4000.
Bryce.
Hi
Thanks for your reply. I was about to test with the twin famicom cable :o
I just bought an "AMSTRAD 464 / 6128 PLUS RGB STEREO" cable so I could test the DIN part.
For the power supply, of course I won't plug the 11V in the 5V socket, :) I promise !
I was about to buy a Universal supply to obtain the 5V but I understand from Dragon answer that I could also test with the 11V supply as this circuit power the Scart / RF (even if we don't have it in France) and the DIN. Is it correct ?
Best regards
Quote from: freenutella on 21:36, 03 June 20
Hi
Thanks for your reply. I was about to test with the twin famicom cable :o
I just bought an "AMSTRAD 464 / 6128 PLUS RGB STEREO" cable so I could test the DIN part.
For the power supply, of course I won't plug the 11V in the 5V socket, :) I promise !
I was about to buy a Universal supply to obtain the 5V but I understand from Dragon answer that I could also test with the 11V supply as this circuit power the Scart / RF (even if we don't have it in France) and the DIN. Is it correct ?
Best regards
If you are using the Monitor DIN socket, then there is no difference between using a 5V or 11V supply. Use what you have.
Bryce.
Thanks :)
Finally I will do the cable by myself as I have an old peritel cable and a DB9 plug.
I will update as soon as I will make the test.
Best regards
I found 2 schema for the cable with does not seems the same.
Coudl you indicate me which one is good one?
The two seems to be for 464Plus or 6128plus
A last question: is the RGB commutation needed? and how should I bring the 5V?
(http://pixnet.fr/pixelworld/img/articles/6128_464_sur_tv/DIN8.jpg)
1 Synchro Composite 16
2 Vert 11
3 Luminance 20
4 Rouge 15
5 Bleu 7
6 Sortie 2
7 Sortie Audio Droite 6
8 Masse 17
and this one
(http://www.cpcmania.com/Docs/Scart/scart2cpc02.jpg)
Best regards
What do you need the DB9 plug for?
You don't seem to have looked at our very own Wiki: http://www.cpcwiki.eu/index.php/TV_SCART_cableI'd (http://www.cpcwiki.eu/index.php/TV_SCART_cableI'd) recommend the "Alternative Wiring" shown on that page because it doesn't need a voltage source, but you will need to change the pinout to match the GX4000 (the diagram is for the classic CPC).
And YES, you definitely need the RGB comms, how else do you intend the colour information to get to the TV??
Bryce.
Thank you Bryce !!
DB9 is an error : I mean DIN8 ... sorry
For the cable I didn't verify the CPC Wiki -> shame on me :-[
For the wiring do you suggest me this one? this one seems to be also for GX4000 and without a voltage source
(http://www.cpcwiki.eu/imgs/9/92/Circuit2.gif)
I have all material needed :) After your answer and I will begin to solder
Best regards
Try it without the voltage source first. If the TV can be manually set to RGB input then the voltage source isn't required. If it's a TV that regularly scans for inputs you may find that it either keeps displaying the "RGB" OSM on the TV screen or the picture flickers (goes black and comes back) every few minutes, then you can always change the cable afterwards.
Bryce.
Hi
To give you an update.
I finally bought an AMSTRAD CPC 464/6128 RGB SCART CABLE for PLUS models.
I plugged it and it works but the screen was really dark (i can see the screen but even with the light at maximum it was really dark)
Do you now with the screen was almost visible?
I decide to retest with a normal scart cable just after and ... It worked perfectly (image is perfect and bright). Strange :o
I will retest tomorrow morning (last time it worked at night but not in the morning).
I try to understand bit I'am a little bit lost.
Best regards,
Im not an expert. But in the service manual luminance appears generated in parallel to the rgb signal.
Maybe something is wrong in these zone. A resistance?. Condenser?, transistor?.
The scart zone should be ok.
What is the iref signal of the dac?
Quote from: freenutella on 18:18, 12 June 20
Hi
To give you an update.
I finally bought an AMSTRAD CPC 464/6128 RGB SCART CABLE for PLUS models.
I plugged it and it works but the screen was really dark (i can see the screen but even with the light at maximum it was really dark)
Do you now with the screen was almost visible?
I decide to retest with a normal scart cable just after and ... It worked perfectly (image is perfect and bright). Strange :o
I will retest tomorrow morning (last time it worked at night but not in the morning).
I try to understand bit I'am a little bit lost.
Best regards,
How are you powering the GX4000 ?
When using the RGB (DIN) output, the GX4000 is expecting to be powered with the 5V supply (from the CM14)
When using the Scart output, the GX4000 is expecting to be powered with the 11V input.
If you use the DIN with a 11V supply, the image will be darker than expected.
On the other hand, using the scart with a 5V will give you an image brighter than expected.
To answer @dragon (https://www.cpcwiki.eu/forum/index.php?action=profile;u=251) question regarding iref : that the reference current that set the relationship between the voltage generated by the DAC according to its input value. And on the GX4000 this reference current is lower when the 11V input is used.
hello
Thanks for both answer.
@Gerald : I powered with the 11V :D and tested first with the Din cable.
My objective was to test the RGB circuit independantly of the scart circuit (the scart output didn't generate image)
I tought it has no effect on the image but it was not the case.
Your explanation is clear : thanks.
I also retest the console this morning with the Scart cable and it also worked.
Finally the console seems to work. I will restest this evening and if it work: I will considered the case closed (but not elucidate).
Best regards
Hello
I tested the console this morning and it worked perfectly!
Thanks a lot for all your answer : they helped me a lot.
Long life to CPC Wiki !!!