GX4000 Not displaying
Pretty sure this is something I am doing wrong but I have a GX4000 that is not displaying when using the Scart connection on either a flat screen or an old CRT tv so could this just be the cable?
Was the machine working with a display before? Do you have a 5v power supply and a Plus style RGB to SCART cable? IF you do try powering the machine with the 5v PSU by connecting it to the GX4000s 5v connection and connect to the display via the RGB connection instead of the SCART. Make sure the 5v PSU is rated at least 1.7 Amp.
This could be either the TVs don't like the display signal or you have what I call the GX4000 "Black Screen Of Death" which seems to be caused by the RGB to SCART decoder IC or associated component failing. In the majority of cases that I have seen, the 5v option and RGB output continue to work. It's just a hunch and I have no solid evidence but I suspect this has something to do with a problem with the 12v side of things.
Thank you for the reply so in effect its a dead device now oh well can get another.
I would try another scart cable before throwing your gx4000 in the bin. ;)
That's on the agenda treid the old CRT TV I use for the BBCs
Treid two different scarts and the RF cable no output other than a black screen so I guess this means a repair is needed or replacement.
I would prefer a repair personally anyone know of any place that can do that?
Yup cover all bases before you write it off! :-) Did you try with a RGB cable connected to the monitor output? If you don't have one, try plugging a set of headphones to the audio out connector at the front of the machine and boot up with Burnin Rubber in the cartridge socket. There is a switch on the back put the headphones on and with the machine powered up try moving the switch both ways, if you can still hear the Burnin Rubber theme tune playing then the machine isn't dead, its just lost its SCART capability!
I cannot hear any music ut I know the sound connector is live moved the cable a bit and got some sound but white noise.
And the monitor I have is the original CPC6128 one the console is getting power.
Ok might be time to consider a new GX4000 then, unless you fancy trying to trace the fault could be something simple, if it was something like a blown ASIC there would likely be some odd things happening on the screen but then again its hard to say.
I personally prefer to power my GX4000s via the 5v socket, I have had the Amstrad PSUs drop to pieces when unplugging them. The power scheme on these machines is pretty eccentric and its all too easy to accidentally attempt to plug the 12v supply to the 5v input, it won't physically fit but you can get enough of a connection to send 12v into the wrong socket which won't do the console any good.
As far as I know the built in SCART will not work when powered by 5v but you just use the monitor output with a 6128 Plus RGB to SCART cable and from your end of things you really shouldn't notice any difference.
If you can't find someone locally, you could send it to me and I'll take a look at it, but I doubt it makes financial sense. For the postage (to Germany and back) alone you could probably buy a new one.
Bryce.
Thanks for the offer I am now bidding a 464+ so here is hoping
I might just send it Bryce only 15,000 of these were made and it would be nice to get it functioning normally again just for that reason alone.
@dcdrac
I'm sure Bryce won't mind as I am in the UK and I believe you are sending me some beebs to repair, if you want to chuck in the GX4000 and a cart in the box too I will diagnose and hopefully repair it for you.
TC :)
OK will do sending one beeb now as a colleague expressed an interest in the other so I gave it to him and hes tinkering with it, I shall be sending both off next weekend via parcel force.
It does seem a crying shame to not at least try to get ti going, it powers on but does not display anything via scart or the UHF cable I have.
Be my guest Corfiot, I'm pretty sure you'll get it fixed too :)
Bryce.
Amstrad gx4000 problems (http://www.youtube.com/watch?v=UyKg46amILI#ws)
Another display issue with the GX4000, some one elses.
It looks like they are hooking the GX up via a composite SCART connector, colour information won't be sent this way as the SCART only outputs RGB. I'm not sure if the part of the clip where they connect the RF cable is supposed to indicate that the problem persists via RF?
That's not black and white, it's green and black, so it's not a composite signal, it's RGB, but R and B aren't coming out. You'd need to trace the R and B signals from the ASIC to the output and find out where it stops. If the ASIC isn't outputing these colours, then it's an ex-GX4000. But my guess is that the video IC has failed.
Bryce.
The R, G and B signals come from a triple-DAC, rather than direct from the ASIC, if I remember correctly.
Well the full path of the RGB is:
1 - ASIC produces a 4bit value for each of the colours (R = Pins 113 to 116, G = Pins 109 to 112, B = Pins 104 to 107)
2 - These get fed into the DAC (IC15 = AMS40464) and leave this IC as 3 analogue signals.
3 - These analogue signals are sent directly to the monitor socket and using some discrete components a LUM signal is also produced.
4 - The analogue signals are also sent to the RGB decoder (IC101 CXA1145) which produces the signals for the SCART socket and a composite video signal which is fed to the RF modulator.
If the colours are missing from all outputs (especially the monitor output), then the problem is most likely with the ASIC or the DAC.
By the way, the CXA1145 also produces a rather good S-Video signal, so an S-Video output mod is very to do on the GX4000, with just some wire and the correct socket.
Bryce.
The thing that made me think it was connected via composite is due to the way it seems to be connected in the video as there is a composite adapter hooked up to the scart output. My theory was that he has mistakenly connected the machine up via the adaptor and is getting a B&W picture on a screen that has a bias towards green (?). Does anyone know if the signal he is showing on the tv is the RF one?
It may be just my ipad screen but it appears that thar tv is flickering between green and black and white?