GX4000 mod not going well console dead? :-(

[Badstarr]

Well I dunno, I followed this guide : How To Make a Real Plus Out of a GX-4000! to the letter, reassembled and fired it up and... nothing happened green light but no screen activity. Then I tied removing the mods, still nothing when I was prodding about I accidentally knocked ASIC pin 130 off its pad and can't solder it back, according to the schematic its a ground so I tried routing it elsewhere and still no luck. So why did it not work??? I'm absolutely certain I followed and reproduced the guide 100% accurately, I just hadn't connected a keyboard.   How frustrating !


So console seems dead, guess I will have to get another, it would be nice if I could figure out why it died! Can anyone see anything wrong with the guide I followed? I would scrutinise it a bit more against the schematic but I'm rather tired now


I just bought another off ebay, this next one better be a success as just paid £50 for it but, I'm at least getting pang with it! can't afford to just chuck £50 away though so I will have to think of something useful to do with the dead one!

[redbox]

Shame to hear that but expect that some other users here can help you with fault testing.


When trying to make my own DIY cartridge, I thought I'd fried some ICs, but in the end when Bryce looked at them for me I'd just done some dodgy soldering.


If you get another GX4000, at least the first one can always be used as a donor for parts should anything else go wrong.

[Zetr0]

I have to admit after reading the guide, the more I want to retro-fit a GX4000 into a CPC464 chassis!

While I am good with electronics, I dont know enough of the CPC hardware yet to really advise you, but what I can say is take some pics and I am sure some more knowledgeable persons will be along to help =)

[Badstarr]

Well I checked the schematic against the guide and I think I can see where there might be a problem. It says to cut pin 159 and reroute it via a resistor to a +5 volt connection. In the schematic there is supposed to be a a 1k resistor (I think that was its value) in series. I think the ASIC may be dead but I have a better idea on how do this next time. To be honest I think I'm just going to follow the schematic rather than the guide. Live and Learn 

[MacDeath]

That's courageous from you but this should teach you this : just buy a 6128PLUS.


GX4000 are rare stuff and it's a crime to destroy some.

Anyway now you have a dead carcass to cannibalize...


ASIC is quite a delicate Chip, so just to heat the stuff to solder some pins can be very damagefull.

I don't know if this is possible but you'd better cut the wire on the printed board than on the chip.

[Badstarr]

You are absolutely right MacDeath! The reason why I'm doing this is I've always wanted to try, as with most of my achievements in the past I just can't give up once I have set my mind on something and occasionally this has been expensive but in the end I have always triumphed even if it was a painful process to get there. I learn a lot along the way too!


I have been looking at the schematics and as far as I can see there is no reason to cut the 159 pin at all, the best way would be to splice in a 2.2k res in line with resistor 17 on the pcb (well this is just off the top of my head from what I remember from the schematics). If it is necessary to cut the connection then i will use a craft knife to cut the trace on the pbc itself like you suggested. The 6128 plus schematic concerning this pin is identical to a stock gx4000 apart from the 2.2k resistor.


Well at least I can now make use of some components eg the RAM ICs, Modulator etc! Every dark cloud has a silver lining!


The saga continues, there is only one way I will see this conclude, with a GX4000 happily humming along as a full CPC even if I devour the worlds supply of consoles in the process, if you want one it may be a good time to buy lol! 

[MacDeath]

While at it, perhaps you can even upgrade the joystick ports so you may get less "keyboard clashes"...

Or even a proper powered mouse port compatible with AMX mouse or Atari ST/Amiga mouse... (or whatever available to you) yet made so the Amstrad see it as an AMX mouse.

[fatbob]

The saga continues, there is only one way I will see this conclude, with a GX4000 happily humming along as a full CPC even if I devour the worlds supply of consoles in the process, if you want one it may be a good time to buy lol! 

So thats the reason I keep missing out at the last minute (7 attempts to buy one so far, 0 successes).

[Badstarr]

Hi fatbob, there are a few on ebay for reasonable cash, this one seems to be roughly the going rate these days just shy of £50 buy it now including postage AMSTRAD GX4000,TESTED WORKING,COMPLETE WITH GAME | eBay . There is also the odd one going cheap on the auctions but there tends to be a bidding frenzy in the closing minutes so it might be a good idea to try and snipe at closing seconds, I've been fairly successful obtaining stuff this way. If I hose the next GX4000 I will try to avoid getting into a future bidding war with you!    Hopefully this will be the last GX4000 I will need as I think I have learned how to make the process easier, heck, it will be all documented in the guide I'm writing along the way so at least I will have some good advice lol!


@MacDeath, I was going to do a built in version of Bryce's PS/2 mouse interface, but what would be cool is if I could have several options, eg, plug atari,amiga,amx mouse etc. What I have been thinking of too is using a scroll wheel for the eventual HxC Installation which would be great for multi functional DSK selection, scroll through, press down to select, only one thing required rather than 3 buttons, space is at a premium in the GX4000 isn't it! 

[TFM]

I tried to omit to read that thread...but by accident I clicked it.

As much as I didn't like to read that thread here, as much you will not like my opinion. But seemingly someone must tell it.

Please stop fecking up all this wonderful and scarce CPC / GX hardware!!! How stupid is that?

If you want to learn how to solder, then please, please do it with some PC trash, but STOP screwing up all these wonderful Amstrad products!!!

It's a shame to do so at all, but to post it here is just too much! Some people shall not solder!

[Bryce]

Hi Badstarr,
        I haven't checked the guide against the schematics, so I can't say whether the guide has mistakes or not. But there is some good news: Unless you've fried the ASIC or something else with the soldering iron, there are very few ways of permanently destroying a GX4000 by making a wrong connection, so chances are, the first GX can still be saved. I would guess (assuming that you didn't fry anything with the iron) that you've possibly caused a short circuit or open circuit somewhere on the board. If you've given up on it, you could always head down to your local Oifig an Phoist with it well packed and send it over. Then I can at least tell you what went wrong.

Bryce.

[redbox]

£50...?!

I bought my GX4000 with Burnin' Rubber cartridge for under £7, including delivery.

Admittedly it was sold as "untested", but it works absolutely fine.

[Badstarr]

Haha! Yup I fecked up but I tend to make my own decisions in life and if I feck up I feck up I don't get down about it, I'm probably going to see if I can get the GX4000 working again. I'm actually very good at soldering.


@Bryce, I'm pretty sure I haven't fried the ASIC etc as I had the iron at a low temperature. I knocked the 130 pin off its pad when I was half asleep at 2 in the morning, when I was using a small screw driver to aid in counting the pins on the ASIC, ( I have to do this sometimes due to a condition associated with being dyslexic ) I received a text on my phone and when I moved to pick it up I scraped it with a screw driver just being clumsy I suppose, anyway I will most likely repair it at some point if I can, it will be easier to do this project without having to trouble shoot the current console so in the interest of getting it done I got the other machine, and getting PANG is a great bonus for me!


Fear not the GX4000's of this world are safe I doubt I will screw up the new one as I have a better idea on how to proceed now. The guide does more or less reproduce the connections on the 6128 plus, however, I have an issue with the instruction to cut pin 159 from the ASIC and reroute it, it seems unnecessary judging by the schematic, and actually misses out R17 which is connected the exact same way on the 6128 plus. If anyone feels different then let me know I welcome any advise that will contribute to a successful outcome!

[CanonMan]

That's courageous from you but this should teach you this : just buy a 6128PLUS.


GX4000 are rare stuff and it's a crime to destroy some.

^^ What he says ^^ 

Seriously, there aren't many GX4000 consoles around to start with, and to waste one on some mad hack-job like this just seems silly to me.

Just my 2p worth.

[redbox]

Well if you look at eBay there are loads and loads of GX4000s for sale and hardly any Pluses.

I think Badstarr's project is great and we can all learn from it. When he's finished, I would definitely like to have a go modding my one...

But I promise to practice soldering on some old junk PC cards first TFM

[Zetr0]

I have to admit my friends, I would love to get a 464 and GX4000 and hack the latter into the bigger chassis.

The GX4000 looks quite ugly compared to the VERY iconic 464!

it would be nice to have all the features of the moto-graphics chipset under the 464 hood, with some very taste-full remodleing...

Hmmm I might see if I can find a *untested* GX4000 and a broken / untested 464 =)

[Bryce]

I can understand modding the GX to a plus if you can't get a plus, but if the case is all that's important, then I'd just get a 6128 which are very easy get and put it in a 464 case. Much less work and more or less the same result.

Bryce.

[Badstarr]

UPDATE: The console is not completely dead! I did a quick and dirty repair again on pin 130, I also noticed 128 and 129 were shorted, probably when I bumped the screwdriver against the asic. This time burnin rubber flashed up on the screen, must be something else not quite right somewhere as it only seems to work every now and then and crashes but at least I can have it working again when I nail down the problem. Off to bed now 12 hr shift in the morning but feeling a little happier!   

[Bryce]

Congrats! As I said, it can only be a short or an open, and neither could damage the GX permanently, unless it was from the 10V supply, but that's only one single track on the whole board. So the chances of it being revived was very high.

It also means you can continue the mod on that device and don't need to buy another one.

Bryce.

[TFM]

Craniums way to make a 6128 Plus out of an GX4000 does definitely work. I saw the machine running and I know him in person. He is professional in electronics/soldering. To solder wires at the pins of the ASIC though is not an easy task and should be done in good physical/mind condition with enough daylight. Then it will work 100% 

[MacDeath]

when I bumped the screwdriver against the asic

You what



Please, why don't you try your moddings on some C64 or Speccy ? please...





Nah, mre seriously, ok you may break some circuit in the process... but your experience will certainly be precious to prevent more damage by peoples who may try  this at home.

The tutorial to mod a GX4000 into a PLUS is old and not that well documented, as it wasn't officially tried more than ... once ?

It is good to get someone try this so we may know what could be wrong or right in it, and have some update and comments on  this...


Sharpen your soldering iron, get the flux flow, clear your mind, deepbreath.... and don't you ever put that screwdriver into this ASIC again evermore !!!!

[Badstarr]

That's good advice MacDeath, I will be more careful should I need to use something to keep my orientation while tracing stuff in the future!


I have scotopic syndrome, I think it mainly effects people who are dyslexic; basically stripes, like the arrangement of pins on the asic for example, seem to jump about or go into a weird 3D effect so I often have to use something to guide my eye so to speak so I dont solder to the wrong part. I actually think what I need to do is use something a little less abrasive shall we say, like for example a piece of tape to line up against the pin I need to solder rather than pointing at it with a (albeit very small) screwdriver.


Fingers crossed for a more smooth run this time!   


Quick Update: This post got me to thinking after I wrote it, perhaps my weird vision problem caused me to route pin 159 to an adjacent point and not a +5v line, I have examined the board and I can see now I've gone and soldered the 2.2k resistor to a ground point not the +5v I thought I had. I haven't got much time to correct this right now and pin 130 is in a delicate state until I fix it down permanently which I think is making this console a bit unpredictable at the moment but, at least I'm armed with this knowledge now and the next console wont meet the same fate! Bering in mind I'm prone to this sort of error I think its going to be a case of "more haste less speed" 

[Gryzor]

Scotopic syndrome - wow, had never heard about it before, but I read a bit and it sounds fascinating... well, at least for a non-sufferer. Tinted lenses, experiments, explanations... wow. It must indeed make it more difficult...

[Bryce]

Never heard of it either, that must make soldering such a tiny pitch a nightmare. Although I have to admit, when I read up on it, my first thought was , where's the issue, other people pay €50 a gram to get exactly this effect. Sorry.

Bryce.

[Badstarr]

Lol! It can be quite mind bending, it only seems to happen to me when I'm really concentrating eg when soldering, or a little on the tired side. Patterns on carpets and wall paper or words on a page turn 3D so yeah, quite trippy dude! It's happened to me when I was driving late at night from work and the road looked like something out of TRON. Even my eye sight is Retro!