CPC6128 12V into 5V socket. Grey Screen

[aleckon]

HI Everyone! New user...been lurking for a while...but never had a problem/questions I couldnt search for. But my luck ran out.....
I have a CPC6128 that had 12v put into the 5V port....I know this because I ordered the wrong power supply from amazon (browsing 5v supplies and this was in the list, right barrel jack size, polarity etc, so amazon suggested it...) and stupidly I plugged it in without double checking the voltage.  

I now have the correct power supply, but obviously I have damaged my CPC.

I get a grey screen with a black border.  No sound, keyboard etc.

Open the case...some hot ram chips about 4 in each bank. 

So I plug in my Dandanator...and the diagnostic test runs...but I never see the ram test part.  I just get alternating border colours and backgrounds that change on each border colour cycle. Also it beeps each change. Starts black then thin and thicker vertical white lines, back to all black screen.  Just runs in a loop.

Anyone seen this?  I will replace the ram chips that are hot (need to get some desolder tools)....but I did expect to see the bad ram detected.

[pelrun]

It's likely that the machine is just rebooting constantly due to the load the shorted ram is putting on the system.

Just get some sidecutters and cut the leads of all the hot ram chips on the top to remove them, then desoldering the pins individually is easy with a normal soldering iron.

The ram test should work at this point, use it to find which of the remaining ram chips still need to be replaced.

[Bryce]

Sounds like you got lucky and only the RAM is damaged.

Bryce.

[aleckon]

Thanks Pelrun.
I did your trick and cut all the hot chips off.  Thanks for the tip around desoldering as well - looks like it will take a while!

The test does still not function as I think it is supposed to - but I do get different screen colour - all white now instead of all black Before it used to cycle black screen and different colour border/backgrounds to thin and thick lines. I no longer get the black screen area - now it is all white and then thin thick white vertical lines with the different colour backgrounds. So its a change I guess

Ill get onto the ram sockets etc tomorrow and see if it makes a difference with them in.

[aleckon]

An update....
Though no change, unfoirtunately.  Got all the hot ram off (...plus an extra chip (1) while I was at it - traces look good etc. 

Havent installed the sockets / ram chips yet, but was hoping that might be enought to give me an look at the ram fault page. Unfortunatley nothing has changed. No change to the diag pattern. Colour backgrounds and screens alternating. No text or faulty ram page. 

Will get the sockets in on Friday and see if 
1. It works! or 
2. I get a different Diag.

Id take either at this point

[Bryce]

An overvoltage can damage a lot in a very short time. I would assume that there is more damage than just the RAM.

Bryce.

[aleckon]

Hey Team...
Well Im away again.

Put in all of the sockets, filled with RAM from aliexpress and ran the diag - unchanged....but for a moment without the dandenator I got a solid blue screen...super interesting. 
I watched some of Noel's troubleshooting videos and fired up the cheap aliexpress hantek oscilliscope (first time using one...had to watch a lot of videos)...hmm...something weird with one of the new ram chips. Swapped it and Voila! Boots to basic and everything is functioning fine!  
I retested using the diag - still have the same repeating pattern...so Im not sure what DIAG that one is...I need to replace it with Noel's as I have no idea what it is trying to tell me

Anyway - thanks for the help / tips....hopefully I stay out of the troubleshooting area for a while