CPCWiki forum

General Category => Technical Support => Hardware related => Topic started by: reno on 21:39, 31 May 19

Title: 6128+ screen blue+green screen of death
Post by: reno on 21:39, 31 May 19
Hi,


I bought an untested 6128 plus recently, and just received a PSU + scart cable.
Unfortunately, it doesn't work. With the Burnin Rubber + basic cartridge, I'm getting this light blue screen with a green border (see attachment)  :(

(https://imgur.com/6DM0GJs)
(https://i.imgur.com/6DM0GJs.jpg)
The previous owner gave me a 12V PSU to go with it, so he probably killed the machine with that thing !  >:(


People on one Facebook group tell me it's probably the RAM chips and I should just replace them.
Other people told me they got exactly this screen with a dead gate array, which would be a bigger problem because on a Plus it means the ASIC is dead, right ?


What do you think ?
Is there any more testing I can do with just a multimeter ?
Any tutorials / links welcome


Thanks !
Title: Re: 6128+ screen blue+green screen of death
Post by: ASiC on 22:27, 31 May 19
Bummer...
Pluses are a bit difficult to repair as almost everything is inside the asic.
Try touching the RAM chips to see if any feels hotter than it should.
Title: Re: 6128+ screen blue+green screen of death
Post by: gerald on 23:06, 31 May 19
Hi,


I bought an untested 6128 plus recently, and just received a PSU + scart cable.
Unfortunately, it doesn't work. With the Burnin Rubber + basic cartridge, I'm getting this light blue screen with a green border (see attachment)  :(

(https://imgur.com/6DM0GJs)
(https://i.imgur.com/6DM0GJs.jpg)
The previous owner gave me a 12V PSU to go with it, so he probably killed the machine with that thing !  >:(


People on one Facebook group tell me it's probably the RAM chips and I should just replace them.
Other people told me they got exactly this screen with a dead gate array, which would be a bigger problem because on a Plus it means the ASIC is dead, right ?


What do you think ?
Is there any more testing I can do with just a multimeter ?
Any tutorials / links welcome


Thanks !
Sounds like a RAM issue to me. To get to this point (screen geometry configured), a good chunk of the ASIC must be working.
Title: Re: 6128+ screen blue+green screen of death
Post by: llopis on 00:22, 01 June 19
Sounds like a RAM issue to me. To get to this point (screen geometry configured), a good chunk of the ASIC must be working.
Yeah, I just repaired a 6128 Plus that was connected to a hard drive power supply (ouch!) and the effects were very similar, just different colors (orange and yellow I think). It turned out to be just 4 really cooked RAM ICs. Everything else was fine. So hopefully that's it.
Title: Re: 6128+ screen blue+green screen of death
Post by: reno on 04:56, 01 June 19
Yeah, I just repaired a 6128 Plus that was connected to a hard drive power supply (ouch!) and the effects were very similar, just different colors (orange and yellow I think). It turned out to be just 4 really cooked RAM ICs. Everything else was fine. So hopefully that's it.


Thanks guys !
Indeed the RAM chips are hotter than they should be. There are just 4 of them, right ?
I just hope that nothing else was cooked by 12V and I'm not going to order RAM and do this in vain !

BTW, I haven't held a soldering iron for 15 years  ;)  Is it difficult to do ?

Title: Re: 6128+ screen blue+green screen of death
Post by: gerald on 10:42, 01 June 19
BTW, I haven't held a soldering iron for 15 years  ;)  Is it difficult to do ?
Just follow the instructions https://www.cpcwiki.eu/index.php/IC_Repair (https://www.cpcwiki.eu/index.php/IC_Repair)  ;)
Title: Re: 6128+ screen blue+green screen of death
Post by: dragon on 15:13, 01 June 19
But not solder the ics back directly. Put a socket. And then you don't need desolder it anymore.

Title: Re: 6128+ screen blue+green screen of death
Post by: reno on 15:35, 01 June 19
Just follow the instructions https://www.cpcwiki.eu/index.php/IC_Repair (https://www.cpcwiki.eu/index.php/IC_Repair) ;)



Thanks, exactly what I needed (well I just need to find the same kind of tips for soldering the socket now. Not even sure if I should solder from the top or the bottom of the MB :/ )


But not solder the ics back directly. Put a socket. And then you don't need desolder it anymore.



Yes that's the plan
Title: Re: 6128+ screen blue+green screen of death
Post by: llopis on 16:48, 01 June 19
Thanks, exactly what I needed (well I just need to find the same kind of tips for soldering the socket now. Not even sure if I should solder from the top or the bottom of the MB :/ )
From the bottom :-)
I would even go as far as saying that you should get a "practice soldering kit" for 5-6€ that would let you practice some basic through-hole components before tackling the ones on the Amstrad.


This one might be perfect. It even has a socket!
https://www.amazon.co.uk/IPOTCH-Digital-Electronics-Soldering-Practice-As-picture-show/dp/B079S7392C (https://www.amazon.co.uk/IPOTCH-Digital-Electronics-Soldering-Practice-As-picture-show/dp/B079S7392C)
Title: Re: 6128+ screen blue+green screen of death
Post by: Bryce on 10:03, 03 June 19



Thanks, exactly what I needed (well I just need to find the same kind of tips for soldering the socket now. Not even sure if I should solder from the top or the bottom of the MB :/ )




Yes that's the plan


Desolder the individual pins from the top (as shown in my article that Gerald linked to), but solder the new socket from the bottom.

Bryce.
Title: Re: 6128+ screen blue+green screen of death
Post by: reno on 05:45, 09 June 19
Desolder the individual pins from the top (as shown in my article that Gerald linked to), but solder the new socket from the bottom.

Bryce.


So I'm a bit ashamed to say, somehow I completely forgot about your article and I did an attempt today the "normal" way, that is to say from the bottom with a soldering pump and wick.  :picard:


It didn't go well.  >:(


I broke at least 2 tracks :
(https://i.imgur.com/XqwiWBq.jpg)
(https://i.imgur.com/yh4GxM7.jpg)


And the bottom doesn't look great either:
(https://i.imgur.com/pq1SJL4.jpg)


And when removing the chips, something from the hole came with it
(https://i.imgur.com/W9ktuP4.jpg)


I ordered conductive wire glue to try and repair the tracks. Or maybe I'll simply have to use wire. But the holes at the top are really, really small.


Do you think the board is still in a repairable state or did I go too far ?  :'(
Title: Re: 6128+ screen blue+green screen of death
Post by: Bryce on 11:34, 09 June 19
Well now you (and everyone else) knows why I tell them to desolder the individual pins from the top. Conductive glue won't work, or if it does, it will be extremely unreliable. You'll have to use wires, but it will be a lot of work and it won't look very good when it's finished.

Bryce.
Title: Re: 6128+ screen blue+green screen of death
Post by: llopis on 12:06, 09 June 19
Well now you (and everyone else) knows why I tell them to desolder the individual pins from the top. Conductive glue won't work, or if it does, it will be extremely unreliable. You'll have to use wires, but it will be a lot of work and it won't look very good when it's finished.
Maybe it won't look pretty, but it's easily fixable. It's only 4 chips, so it won't be that many cables. I'd say it's worth a try.
Title: Re: 6128+ screen blue+green screen of death
Post by: reno on 16:31, 09 June 19
Believe me guys, I've been banging my head against the wall since yesterday, I don't know how I could forget your advice from 1 week ago.  :doh:  Maybe because I've read and watched so many things since, and I was focused on cleaning the PCB first.

I really hope I can save this CPC... I've already cleaned up the keyboard, case, changed the drive belt with a new one, cleaned the PCB using WD-40 contact cleaner then isopropyl alcohol.

But, because this CPC has had 12V applied by the previous owner, maybe I'm doing all of this in vain. Even if I managed to replace the RAM and repair the tracks / fix my mess, maybe it's not just the RAM that got killed by 12V ? And maybe the heat during desoldering killed more ICs.
Do you think it's worth trying ? Or would one of you be interested in buying it for spares ?

Assuming I'm gonna try some more, I think I have 2 problems now :

Problem 1 : The 2 broken tracks going from pins 2-3 of IC11 to the 2 smaller holes above. On the bottom side of the board, 2 tracks then go from these 2 holes to the group of 5 holes above R56. Then on the top side again, 2 tracks go from there to the ASIC.
What do you think is easiest ?
Option A : repair the original tracks on the top side of the PCB, using ... I don't know what ? A very small wire directly soldered flat along the PCB track (like this guy did (https://www.youtube.com/watch?v=a5A61fIu0kk), but it looks really difficult to me) ? Or a short jump wire, like this (https://www.youtube.com/watch?v=KRSQOOY67DU), but it's already going to be a busy area on the top side, so maybe better to do this from the bottom side ?
Option B : Bypass the broken tracks and directly connect 2 longer jump wires directly from pins 2-3 of IC11 to the 2 small holes above R56... this also bypasses one of the bottom tracks which I think could be damaged too. Again, better to do this from the top or the bottom ?

Problem 2 : I have at least 8 missing copper eyelets that came from the holes when I pulled the ICs. I have recovered most of them but I'm not sure if it's enough to just put them back in. Some are pretty damaged. Are they 100% needed, can I not replace them with more solder alongside the socket pins ?

Here are photos to illustrate (scroll from left to right if needed)

(https://i.imgur.com/3EtXWYv.jpg)








(https://i.imgur.com/MM3nBv3.jpg)


What do you think ?
Thanks for your help, and fingers crossed !

Title: Re: 6128+ screen blue+green screen of death
Post by: Bryce on 18:07, 09 June 19
The torn out vias are useless, throw them away. Firstly, for every via that actually connected a trace on BOTH sides of the PCB you'll need to find a point on each side where you can join them with a link wire. Luckily in most cases here they probably only had a trace on one side. After that, when the sockets have been installed, solder jump wires from each of the pins that have a damaged via/trace to the nearest solder joint on that circuit. Don't solder to a via, use a proper pin such as the next resistor.
As for heat damage to other OCs. This is unlikely, the heat drops as it travels along the copper and is unlikely to have damaged anything else. Whether or not the 12V has fried anything else is hard to say. You only find out when the RAMs are back in place.

Bryce.
Title: Re: 6128+ screen blue+green screen of death
Post by: reno on 18:57, 09 June 19
The torn out vias are useless, throw them away. Firstly, for every via that actually connected a trace on BOTH sides of the PCB you'll need to find a point on each side where you can join them with a link wire. Luckily in most cases here they probably only had a trace on one side. After that, when the sockets have been installed, solder jump wires from each of the pins that have a damaged via/trace to the nearest solder joint on that circuit. Don't solder to a via, use a proper pin such as the next resistor.
As for heat damage to other OCs. This is unlikely, the heat drops as it travels along the copper and is unlikely to have damaged anything else. Whether or not the 12V has fried anything else is hard to say. You only find out when the RAMs are back in place.

Bryce.


Ah ok, thank you for all of this.
So, I definitely can't replace a via with some solder or wire that goes through the hole and connects both sides ?


What about the damaged tracks ?
In the case of the 2 damaged tracks from pins 2-3 of IC11, I don't think I have a choice but to solder to a via, because the circuit ends up at the ASIC on the other side (pins 98-99), and I can't possibly solder directly on an ASIC pin, they're too small. Even these small vias will already be a challenge to solder to I think, because they're so close together.
The only other option is to repair the track I guess.
Title: Re: 6128+ screen blue+green screen of death
Post by: Bryce on 13:31, 10 June 19
The vias you've destroyed will have a socket pin going thorugh them, so you just need to solder to both/either side of that pin. If the circuit goes directly to the ASIC with no components between, then solder to the via, ASIC soldering isn't a good idea.

If you decide the job is too much of a challenge and you want this board working, you can send it to me for repair.

Bryce.
Title: Re: 6128+ screen blue+green screen of death
Post by: Overkill on 16:58, 17 June 19

@Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225) How much would you charge for a board fix?  I bought a non-working 6128 Plus and thought it might just be the RAM, but I assume a few of the vias and tracks must be damaged, because it has small repair wires on the RAM chips, so I didn't fancy going any further.


Sorry reno to butt-in on your topic :)

Title: Re: 6128+ screen blue+green screen of death
Post by: Bryce on 09:28, 18 June 19
@Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225) How much would you charge for a board fix?  I bought a non-working 6128 Plus and thought it might just be the RAM, but I assume a few of the vias and tracks must be damaged, because it has small repair wires on the RAM chips, so I didn't fancy going any further.


Sorry reno to butt-in on your topic :)

PM sent.

Bryce.