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avatar_twox

Me and my Schneider CPC 464 again.

Started by twox, 16:17, 12 January 19

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Bryce

You should have told me and I could have included some in the package.

Bryce.

twox

Well, i look forward to replacing the AY the same way a convict waits for trial (and sound isn't that vital for playing around with MAXAM).. It will definitely clear some things out but may also fuck up everything. I already had a nightmare where i press a key andddddd ttttttttthhhhhhhiiiiiiiiiissss *coughs* happens. Good thing that the AY chip is not as small as those pesky RAM. Cheers

Bryce

If you haven't read this before, then read it before you start your "conviction trial": http://www.cpcwiki.eu/index.php/IC_Repair
DON'T try to remove the old IC in one piece, you will definitely damage the PCB, and that's not a good idea.

Bryce.

twox

Youre not the only one that heard horror stories about people removing IC's by placing them above gas stoves..
Dont worry, i have read your guide more times than i have fingers. And, i still have 20 of them, despite that the fact that the rest for hot soldering iron i just bought tried to dec that amount.
Spoiler: ShowHide

twox

#54
Is it normal to fuck up the first time?Now, when i turn the computer on i get all kinds of weird situations.. Weird characters appearing on screen, a loud hum from speakers (and the whistle did not change at all), keyboard not working, keyboard partially working or not at all, the sound is working or not. At least one time it worked as good as before, and that wouldn't be the case if i fucked up something else. I think that one of my solders is bad, the pin 14 doesn't have almost any solder on it.
I also noticed that my mainboard is sticky and has a white residue on it, i suspect that the "ethanol" i used to clean it has some additives. I will buy some proper isopropyl for cleaning electronics, and correct my solders. If this wont fix the issue, i am at risk of devoloping alcoholism.
Are the solders supposed to be big and pear-shaped? Because all of mine are small and flat, and in like 4-5 pins i still can see the inside of board. Truth to be told my hands were shaking like crazy and i wanted to finish the job ASAP, so applied very little solder.

LambdaMikel

Quote from: twox on 20:33, 21 February 19
I also noticed that my mainboard is sticky and has a white residue on it, i suspect that the "ethanol" i used to clean it has some additives. I will buy some proper isopropyl for cleaning electronics, and correct my solders. If this wont fix the issue, i am at risk of devoloping alcoholism.


If this is your first time using a soldering iron, then I'd suggest to start with something more simple first, or let somebody else do the the job.


For the cleaning, take out the whole board, turn on the shower with WARM WATER, a clean soft brush, some liquid soap, and shrub it down. When clean, shake of as much water as you can, put it on a towel, and then use the hair dryer. This procedure works best for thorough cleaning of a f****** motherboard.


The only thing that can get negatively effected by that are some old electrolytic capacitors, which need replacement anyways.




Bryce

Sounds like your solder joints aren't good. You should not be able to see into the hole if it's done properly.
Here's a one page guide...

Bryce.

LambdaMikel

There should also be a YouTube video somehwere....

twox

I really hate to bring news this bad...
The repair was botched completely, but at least it was not completely my fault. Initially i mistakenly made like 3-4 bridges (nothing you couldn't save), but then the person who i asked to help almost dragged me out of the chair and tried to proceed with the repair. Results - at least 1 track pulled out of PCB like a thread from fabric, at least 4 scratched, God knows how many burned, and like 1/2 of the copper sleeves inside of PCB (i dont know how they are called) missing. The only hope of repair is to wire the thing together, good thing that there are schematics. The AY's original place in the board is broken beyond any sensible repair (at least for me). I fell like a let down, i managed to make a problem even worse than it was (and injured myself in the process of doing so)... At least there is one good news - the AY isn't the culprit of whining.

Will wiring it together do any good?


LambdaMikel

Seems your CPC is ripe now to receive the miracles of Bryceification (if he accepts it)  :D

twox

#60
Quote from: LambdaMikel on 18:14, 22 February 19
Seems your CPC is ripe now to receive the miracles of Bryceification (if he accepts it)  :D
This definitely would be one of the messiest jobs..
I fell like shit for having to do it 2nd time... Especially that what he would see upon opening the packet would be the effect of EXACTLY what he have just told NOT to do (aka unsoldering from the bottom). I told the person that tried to help me that the tracks are going to be raped, but by that point i was iterchangeably hyperwentilating and panicking, and couldn't do anything to stop it (because the helper had much more experience in soldering, and i had none - therefore my voice didn't count). To recap the whole botched job;

       
  • I cut all the pins of old AY
  • I remove the old solder and clean the sockets with desoldering pump
  • I solder in the socket and put in the AY, by that point the fault was some bad joints
  • I tried to correct it once, but without any effect
  • I tried to correct it once again, but this time i accidentally created some bridges between the board and body of the socket (solder leaked thru the hole when i was soldering)
  • My helper took the job, and decided to remove the socket completely
  • He tried to unsolder it from the bottom to no avail, burning all solders and possibly the traces leading to them
  • He ripped it out with pliers, destroying from 3/4 to all holes and severing 3-6 traces.

Bryce

Try not to get "help" from that person any more, I think he is overstating his electronics skills. I have no problem with you sending me the PCB again if that's what you choose to do.

Bryce.

Bryce

Oh.  :picard:

Your PCB just arrived. For anyone who didn't get my message: Never unsolder an entire chip from the bottom unless it's a single sided PCB. And this is why.

Bryce.



Bryce

Not that the bottom of the board looks any better. Not a single via survived. Work ahead, iron fired up...

Bryce.



twox

Well, now my only option is to beg pardon..But in exchange (that also counts as part of VERY GOOD DEAL), you can use those images in your IC desoldering tutorial as an example of what happens if you try some counterintuitive (and counterproductive) means of repair. :P

Bryce

True. I've started fixing it up tonight, but it's a long job, so I won't be finished for a few days. Then I'll post a picture of the repaired board. All repairable by the way.


Bryce.

Bryce

#66
Well it's back to a working state again. From the top it looks like new. From the bottom less so.  ::)
I'll try to hook up some sort of amplifier and see if I can find the whining noises now.


Bryce.


Audronic

@Bryce


Ahhhh Al Dente. 

Well done. Youch.
Very neatly laid out
Well done

Ray
Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

twox

It doesnt have to look good, it is a veteran now!I think it deserves a DDI disk drive now - i'll have to spend some more money.Thanks and Cheers

twox

Have you identified the whine? I was using a old cheap speakers and it was hearable so you needn't test beyond that. With external speakers it wasn't that bad tbh - there was a volume where the correct sound were hearable and well although quite quiet, and the whine wasn't hearable at all.

Bryce

I'll hopefully get around to it this wekend.

Bryce.

geebus

WAW! Kudos @Bryce that is a hell of a repair.A good case of Verschlimmbesserung!
How is the chip now held in? was there anything there to solder back on to hold it in place?
This is a good lesson for me seeing this. I started tinkering with some broken amiga 500's that need work. So, if I make them worse it's not the end of the world.
I didn't know about de-soldering from the back, although, i'm not sure how i'd get the capacitors out without doing so as there is no access from the top. Also, the negative soaks up all the heat when trying to de-solder that side.
ANYWAY i'm off on a tangent again, as I always do.Would love to see the end result!

Bryce

Quote from: geebus on 14:20, 09 March 19
WAW! Kudos @Bryce that is a hell of a repair.A good case of Verschlimmbesserung!
How is the chip now held in? was there anything there to solder back on to hold it in place?
This is a good lesson for me seeing this. I started tinkering with some broken amiga 500's that need work. So, if I make them worse it's not the end of the world.
I didn't know about de-soldering from the back, although, i'm not sure how i'd get the capacitors out without doing so as there is no access from the top. Also, the negative soaks up all the heat when trying to de-solder that side.
ANYWAY i'm off on a tangent again, as I always do.Would love to see the end result!

Soldering from the back is only important when you're talking about components with many pins. With capacitors, you usually pull one pin at a time and there is no issue. The socket in this case has no solderable holes that could hold it in place, so the socket was held in place with superglue plus the fact that I bent all the pins. Otherwise it's technically floating.

Bryce.

||C|-|E||

I really like the layout of the blue cables, it looks really neat and cool!  :D

Bryce

#74
So twox... I proded your board with some pointy things and even waved a nearfield probe over the surface. Whatever whining you can hear isn't coming from this PCB. I suspect that the issue is on the tapedeck PCB. Probing the outputs of channels A/B/C gives the normal random mid-frequency hum that all CPC's (all AY's to be exact) give off, but not louder than expected (around 40mV at highest peak) and they are all random, no pattern that could cause a tone. The second test was to see if anything else was transmitting a whine that could be picked up by other components, but the spectrum shows just the two expected peaks at 2Mhz and 4Mhz which are harmonics of the main clock.

As a very last test, I'll see if I can find my signal tracer and prode around the board for audible tones. (assuming I can find it)


Bryce.

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