Killed my CPC 464.. help with diagnosis please

[LambdaMikel]

 
I knew it was going to happen one day... and this was NOT caused by LambdaSpeak hardware development.
I simply confused 4.5 V  position on my PSU with the 12 V position... that didn't go to well with my 464 
It still powers up, but shows gray screen. See screenshots attached. Any ideas, what's the most likely component that I fried? So stupid... well I still have some other CPCs, but that was my favorite  Please help me fix it.
Thanks, friends!

[Bryce]

Candidate number one is the RAM. If you are really lucky one of the RAMs shorted and stopped the 12V from damaging anything else.

Bryce.

[LambdaMikel]

Candidate number one is the RAM.

Thanks Bryce.
Is there a straight forward way to figure out which RAM chips got burned, using logic probe or similar?
Also, can I just use the RAM from another CPC, are they all compatible? (Same question I would have
about different Gate Array / ASIC / ... versions - all plug and play and 100% pin compatible?)

[ASiC]

Is there a straight forward way to figure out which RAM chips got burned, using logic probe or similar?

Usually when a RAM chip is dead, it tends to heat up, way more than the good ones.
Give 5v to the motherboard and take temp readings of the chips.


You might be able to tell just by touch.

[LambdaMikel]

Same question I would have about different Gate Array / ASIC / ... versions - all plug and play and 100% pin compatible?)

Seems the answer is no:
http://www.cpcwiki.eu/index.php/Gate_Array_and_ASIC_Pin-Outs

[LambdaMikel]

Looking at my board, it seems it has support for 40010 and the older 40007 and 40008!
Has anybody tried swapping another Gate Array into the empty extra socket before?
I am asking because I still have another 40007 / 40008, but no 40010 for Gate Array testing.

[Audronic]

Have a look here
Gerald Ram Test ROM


Quick and dirty RAM test for CPC


Ray

[LambdaMikel]

Great, thanks for the link the MEMTEST.bin
Now I only have to figure out how to burn a lower ROM with my XMem.

Btw, the RAM chips indeed all get quite hot.

[LambdaMikel]

Can someone give me hint how to install RamTest.bin please? I have an XMem. I am using "exrom.bas" from XMem tools disk A, and then it shows that ROM 0 = 64,  ROM 1 = 01, and LOWER ID = 71. So after "filename? " I loaded ramtest.bin, and tried all 3 IDs, but when  I booted in XMem boot mode, I either got a pixelated screen or colorful vertical stripes. What am I doing wrong? I am using a 6128.  After that, I have to run "setup" from XMem tools disk again, in order to get the XMem Firmware 3.14 back again, so it seems to be replacing some system roms, but it doesn't work.

[CraigsBar]

Can someone give me hint how to install RamTest.bin please? I have an XMem. I am using "exrom.bas" from XMem tools disk A, and then it shows that ROM 0 = 64,  ROM 1 = 01, and LOWER ID = 71. So after "filename? " I loaded ramtest.bin, and tried all 3 IDs, but when  I booted in XMem boot mode, I either got a pixelated screen or colorful vertical stripes. What am I doing wrong? I am using a 6128.  After that, I have to run "setup" from XMem tools disk again, in order to get the XMem Firmware 3.14 back again, so it seems to be replacing some system roms, but it doesn't work.

Flasher from the disc can do it. Program the required lower rom into slot 7. The xmem does not remap slot 7 as only a small number of cpc 6128 machines can support it. So the xmem uses slot 7 for the lower rom.

Sent from my ONEPLUS 3t using Tapatalk

[LambdaMikel]

Thanks guys. OK, so I tried |flash,"ramtest.bin",71 (= &47) and after that, when I boot the 6128 from XMem
Boot, I am getting pixelated screen.

[LambdaMikel]

OK, figured it out by now... it was my DSK / HFE image creation process which was bad.
Was able to flash and run it  now - thanks to all who helped!

Unfortunately, I am seeing a lot of red... probably not a good sign, uhh? 

[LambdaMikel]

I think from this we can assume that I burned ALL my RAM chips??   

[Audronic]

No Not yet


Just replace 1 (One) Ram Chip and re run the RamTest.
Good luck


Ray

[||C|-|E||]

It could be a good time to install socketed RAM though  . I mean, Bryce always says that if it is not broken don´t fix it, and it could be that only one chip is damaged. However, nothing stops you now from removing all of them and install new ones. Even if only one chip is not OK, you will probably heat all the others by removing and reinstalling it and since you have the board outside and so on... 

P.D: besides, a board with only one socketed RAM chip does not look nice! 

[robcfg]

I do agree.


While you are at it, socketing the ram chips will make your life a lot easier while trying to find the faulty ones.

[LambdaMikel]

However, nothing stops you now from removing all of them and install new ones.

Only my extremely bad desoldering skills. I am ok soldering, but never figured out how to desolder properly. I already damaged 2 trace trying to remove the first RAM chips... I am afraid I won't have enough time to do this (took me 2 hours for one chip - family is getting mad) 

[pelrun]

If you're desoldering a bad through-hole IC, don't even bother trying to take it out in one piece. Use sidecutters to cut all the pins, then you can remove each pin individually.

[LambdaMikel]

Thanks Pelrun, thats a great suggestion.

[||C|-|E||]

To desolder, what I like to do is to use quite a lot of braid and flux  . Before cutting the pins of the ICs, I remove as much solder as I can with the braid and then I proceed to cut. This is good because it prevents tensions on the board that otherwise can appear when cutting. Once the IC is completely gone, I take the pins, one by one, with a pair of pliers. You grab the pin, heat it a little bit with the iron and it is dead easy to remove it. Having the proper cutter it is very important too. Actually, if the tool is very good, you can cut the pins without removing the solder first, but I prefer to do it anyway.

I removed the IC from this 6128 board using the technique above and, as you can see, it looks nice and clean 

[LambdaMikel]

Once the IC is completely gone, I take the pins, one by one, with a pair of pliers.

Thanks, that is a good technique - I used tweezers, and it worked pretty well. The remaining pin fragments from the ICs I was able to push through by heating the solder point and pushing some wire through, such that I could pick it then up from the other side. Thanks for suggesting it. All solder points are empty now.

Now I need to remove more solder because the holes are still blocked by solder. Desoldering braid is difficult to handle, too, IMHO. Maybe I have the wrong iron for that kind of work... I have this pump, but frequently it doesn't suck up all the solder. Just enough for the hole to remain to be blocked 

I guess before putting in sockets I will also need to figure out how to reconnect the two brocken tracks / traces.

Btw, the 40010 Gate Array didn't get damaged -  I tested it in a 6128. No problems.

[Audronic]

I guess before putting in sockets I will also need to figure out how to reconnect the two brocken tracks / traces.

Hi Mike

I just run a length of wire wrap (Kynar Wire .025mm  30AWG) or equivalent (Solid Insulated wire).

From the pin on the socket back to where the Track (Trace) starts , Please don't try and fix the Track (Trace)
Good luck

Ray

[Bryce]

Thanks, that is a good technique - I used tweezers, and it worked pretty well. The remaining pin fragments from the ICs I was able to push through by heating the solder point and pushing some wire through, such that I could pick it then up from the other side. Thanks for suggesting it. All solder points are empty now.

Now I need to remove more solder because the holes are still blocked by solder. Desoldering braid is difficult to handle, too, IMHO. Maybe I have the wrong iron for that kind of work... I have this pump, but frequently it doesn't suck up all the solder. Just enough for the hole to remain to be blocked 

I guess before putting in sockets I will also need to figure out how to reconnect the two brocken tracks / traces.

Btw, the 40010 Gate Array didn't get damaged -  I tested it in a 6128. No problems.

If you cut the pins at the right point you don't need to poke the pins out with wire. I did a tutorial (with pictures) here of how to do it: http://www.cpcwiki.eu/index.php/IC_Repair

Bryce.

[LambdaMikel]

If you cut the pins at the right point you don't need to poke the pins out with wire. I did a tutorial (with pictures) here of how to do it: http://www.cpcwiki.eu/index.php/IC_Repair

Very useful tutorial! Yes, I didn't have these very fine cutters, so I couldn't get too close to the pins somehow. Need to get better equipment for that kind of job.

Has anyone ever tried compressed air to blow out the solder from the holes? This is really the hardest part of the job I think.

Bryce, what kind of iron are you using for the wick. It never seems to be doing a lot for me. Maybe the tip of my iron is to fine, or it doesn't have enough watts?

[00WReX]

Not sure what desolder wick/braid you are using, but the difference between good and bad is night and day.
Or more importantly, the difference between removing solder really easily, or actually destroying a board...and I am not exaggerating.
I once purchased some cheap Chinese braid, that you could probably call a clone as the labeling looked similar to a brand name one.
It was simply unusable, and if I had persisted, would have started destroying things.

My brand of choice is Goot Wick.  I actually, swear by it.
I just recently removed all eight RAM chips in an Atari 800XL with this alone and it took me roughly an hour and a half.
And that was non destructively removing the chips, in the end I re-used seven of the eight as only one was dead.
I even have a cheap desolder station that works well, but for me, the wick is my go too.

Cheers,
Shane