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General Category => Technical support - Hardware related => Topic started by: berks on 13:48, 02 September 21

Title: GX4000 LED on but no video over scart
Post by: berks on 13:48, 02 September 21
Hi folks,


I have recently got my hands on a battered gx4000. I tested it today with one of those multi-voltage adapters (positive in, 11v on the 11v port) and a scart cable to an old LCD that seems to support RGB over scart. The console powers on (green LED on) but there is no signal on the TV at all. I power it on with a Robocop 2 cartridge in the slot.


Any ideas what could be the problem here?

Edit to add: I have a CTM640 on my CPC464 and the thought just crossed my mind... would I be able to use the CTM640 with the GX4000?
Title: Re: GX4000 LED on but no video over scart
Post by: Bryce on 13:53, 02 September 21
Yes, you can use it on the monitor, but you'll need an adapter. Are you getting any picture on the screen? Blue background or whatever?

Bryce.
Title: Re: GX4000 LED on but no video over scart
Post by: berks on 22:35, 02 September 21
Hi Bryce,


Unfortunately there's nothing on screen and the TV shows the "no signal" message.


I'll spend some time with it this weekend and report back any progress, but I'm not too hopeful :-)
Title: Re: GX4000 LED on but no video over scart
Post by: Marian on 23:00, 16 January 22
Hi Guys,
having exactly the same symptoms however trying via Scart to an old Sony CRT. But unfortunately no luck ;( Have checked Voltages on the Diode D183 and C128 as well LM8705 and having 9V and 5V. Just black screen. What else can I check ? (Revision A -board PAL without TV modulator ;(
Title: Re: GX4000 LED on but no video over scart
Post by: Bryce on 10:37, 17 January 22
What test equipment do you have?

Bryce.
Title: Re: GX4000 LED on but no video over scart
Post by: Marian on 12:00, 17 January 22
Hi Bryce,


Just a regular Multimeter/Soldering Iron and C4CPC however as no video it`s quite hard for me ;(
Title: Re: GX4000 LED on but no video over scart
Post by: dragon on 12:24, 17 January 22
Try put the burning rubber in a slot directly in the c4cpc.


Then put a headphone in the audio jack and view if you can hear the burning rubber sound.


Thats little easy test to know if the console is working in some manner and if the problem is in the dac, the sony chip or something in the out video part...


The headphone jack is connected practically directly to the ay chip same as the monitor connector.


It there is not sound the problem is more back, asic, RAM, z80.. Or something else.
Title: Re: GX4000 LED on but no video over scart
Post by: Marian on 16:45, 17 January 22
Hi Guys,
[/color] Have tried that out ...I see red light flashing for 1-2sec on the C4CPC (D3)and hear a short 0.1sec. short electric buzz trough the headphones however no real sound ;( Any other suggestions what I could try out ?
[/size][size=78%]Ps>thanks already for all your knowledge and help.[/size]
Title: Re: GX4000 LED on but no video over scart
Post by: dragon on 17:28, 17 January 22
That's because the z80 try read de c4cpc at least.


The gx4000 the first do was read the cartridge.


Try these ram test and view if something is displayed.


https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/quick-and-dirty-ram-test-for-cpc/
Title: Re: GX4000 LED on but no video over scart
Post by: Marian on 19:05, 17 January 22
Hi,


Have tried this RAM test...
https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/quick-and-dirty-ram-test-for-cpc/msg106676/#msg106676

however unfortunately still nothing just black screen ;(
Title: Re: GX4000 LED on but no video over scart
Post by: Bryce on 20:09, 17 January 22
Where are you located?

Bryce.
Title: Re: GX4000 LED on but no video over scart
Post by: Marian on 00:01, 18 January 22
Hi Bryce,


Slovakia...(east of Czech)
Title: Re: GX4000 LED on but no video over scart
Post by: Bryce on 19:58, 18 January 22
Quote from: Marian on 00:01, 18 January 22
Hi Bryce,


Slovakia...(east of Czech)

Ok, if it turns out to be something other than the ASIC (ie: fixable), you can send it to me (in  Germany) for repair without any customs issues. However at the moment it sounds like an ASIC problem.


Bryce.
Title: Re: GX4000 LED on but no video over scart
Post by: Bryce on 13:07, 05 February 22
Hi Marian,
I just took a look at your GX4000. You didn't mention that it had already been attempted to be repaired by someone who really shouldn't be allowed near electronics. Here's a close-up of the RAM pins. They are mangled and most of the traces are broken. I'll evaluate exactly how much damage this person did and let you know later if it can be saved. The "butcher" didn't stop at the RAM, there's several other parts around the power regulator which were swapped too.

Bryce.


Title: Re: GX4000 LED on but no video over scart
Post by: Animalgril987 on 19:06, 05 February 22
Jeez, that guy should have his soldering iron confiscated.
Title: Re: GX4000 LED on but no video over scart
Post by: Bryce on 15:01, 12 February 22
First analysis after removing the RAM IC's: IC110  9 out of 18 pins weren't connected. The red arrows are the pins where the entire pad and via were ripped out of the PCB. The yellow arrows still have the via, but it's no longer connected to the trace. Why would anyone think that this was going to work?? If you don't know that the current is travelling through the copper, then you really shouldn't be anywhere near electronics.

I should mention, Marian bought this GX4000 in this condition, he didn't do this butchery.

Let's see if it still works when everything re-attached as it should be. Unfortunately, those black marks are where the PCB has been burnt, which means that the butcher put massive amounts of heat into the board which may have caused other issues.

Bryce.

Title: Re: GX4000 LED on but no video over scart
Post by: Bryce on 16:42, 12 February 22
So... Unfortunately after soldering many jumper wires I was able to test the board and... The ASIC is fried :( I suspect the original owner had given it the typical >9V into the 5V socket. Having almost identical power sockets with one of them being a completely unprotected 5V input has to be the most stupid design decision that Amstrad ever made.  :picard:

Bryce.
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