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Old 08 January 2009, 11:58   #1
Molcos
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Amiga 1200 and broken audio. *NOW WORKS*

Hello.

Bought a amiga from Ebay a while back and have tinkered a bit with it and added a internal CF card adapter +4GB Sandisk Ultra2 + a Blizzard 1230 IV and installed OS 3.9.

But the problem is that the audio seems broken, it sounds distorted and the music is like if you try and play it through a cellphone with bad reception.

I tried both L and R by itself and they produce different sounds wich indicates that the stereo function is working but they are still broken in the same way.

I have read in the forum that there are capacitors that have a tendency to go bad, but i have no idea on how many there are or the location of them on the motherboard.

I have ordered a new motherboard from ebay and hope that it will solve the problem, but i still would like to find some information on how to eventually change the capacitors on the motherboard.

I have a 1D1 revision of the board.

Regards Marcus

*EDIT*
The 1200 works if i connect a different supply, tested with a ATX 500w.

Last edited by Molcos; 10 January 2009 at 18:24.
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Old 08 January 2009, 15:43   #2
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I believe it is the audio capacitors that have a tendency to leak and cease to work, but I'm no expert. Zetr0 is the one to ask + he's the Amiga Pr0n master 'n' he'll be able to point out which ones they are if there is no visible leaking coming from them

Maybe PM him pointing him to this thread mate!
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Old 08 January 2009, 15:47   #3
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Will do asap, thanks for the info.
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Old 08 January 2009, 16:00   #4
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Molcos, your problem is 100% related to the audio capacitors...I had the exact same problem..replaced the caps and all is fine now
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Old 08 January 2009, 17:20   #5
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Yay! I new I read this somewhere. Excellent, now all he needs to know is which ones to change and maybe how to clean the acid off the mobo, if it's got any on of course
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Old 08 January 2009, 17:25   #6
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OK i will open the Amiga up again and check the board and see if i find anything.

I can take some macro photos and post here for some feedback since i dont know which ones are related to audio and whatnot.

But it was like 10 years since i held a solder iron in my hands.
I hope it's no rocket sience to solder them of.

Last edited by Molcos; 08 January 2009 at 17:32.
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Old 08 January 2009, 17:30   #7
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Good idea mate!

Piccies are always a good thing when needed, I'm sure we'll be able to sort all your problems out mate 'n' get that Amiga working properly once again
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Old 08 January 2009, 21:19   #8
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Ok i have opened the little bugger and took some pictures.

The thing is that those capacitors looks fine to me. (might still be broken tho)
The components right behind the Audioports looks REALLY bad, looks like they have been replaced and soldered back on by a drunk. (Pictures shows em)

I have no idea if those are the culprits or if it's something else.

I kept the images big for easy viewing ^^ (took forever to upload)


Free Image Hosting by ImageBam.com
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Old 08 January 2009, 21:49   #9
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MMM Someone has had a good hash at trying to repair this fault before!!!!!

They have evn melted the housing of the Keyboard connector with the iron body.

It's possible that the caps are the root cause of the problem but unsure if Mr "drunk" has introduced further faults....

Try using a meter to carry out continuity tests on the re-worked area, may need to find an A1200 schematic methinks too.

TC
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Old 08 January 2009, 22:10   #10
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Might also try metering your PSU.


The -12v rail is what drives the audio section. If its off very much (or a lot) it can also cause those types of problems.
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Old 08 January 2009, 22:25   #11
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ok, hm got to get a multimeter to cary out further testing.

does anyone know what those mangled components are for?

Thanks for the help so far.
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Old 08 January 2009, 22:36   #12
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Before going any further, make sure you test the voltage out out of your PSU.




Might as well test all of them. Especially the -12 volt one.
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Old 08 January 2009, 22:40   #13
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Perfect, thanks for the picture of the psu connector.

Dammit why don't i have the essential equipment at home to test this...sigh.
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Old 08 January 2009, 23:29   #14
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Cheers for the piccies Molcos, looks like someone has really tried to butcher that poor mobo mate!

Whoever did this to the Amiga probably destroyed any chance of him (the drunk) repairing it

But with the thanks of us EABer's I'm sure the fix is going to be a simple one. To me, the solder joints on the surface mounted components are totally useless. So I would be trying to remove them and re-sit each one carefully and solder them back on again using very little solder and DON'T keep the iron on for too long 'cause you'll only burn the component and destroy them + you can damage the tracks, eyes when there and mobo. However, if you are not confident enough to do it (It will and does take skill and a steady hand), I would get someone who can replace/re-sit the components for you, someone who works in the electronics trade especially those who repair the surface mounted stuff. Take it from me, I have done this and it's no joke doing it.

btw. If you are doing it ,you'll also need it well lit and a good magnifier too, just so you can see everything properly and have a friend/wife there too just to hold it for you, this will make them think they are important and helpfull
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Old 08 January 2009, 23:52   #15
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Quote:
Originally Posted by DemonHellraiser View Post

btw. If you are doing it ,you'll also need it well lit and a good magnifier too, just so you can see everything properly and have a friend/wife there too just to hold it for you, this will make them think they are important and helpfull


Sorry DH / all, I couldn't help it Fnar Fnar

TC
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Old 08 January 2009, 23:53   #16
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He he.

If i do it myself i have to buy all the stuff, and risk destroying the mobo for good.
Leaving the mobo to a company that do this stuff is probably my best shot depending on the cost of doing it.

Btw do you know what those components are? if i remove them i rather replace them with new ones then to use the old ones again.

Thanks for the support.
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Old 08 January 2009, 23:54   #17
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I can see it too Just when you type it 'n' read it back it looks OK. Maybe I should of added the bit about the tweezers too, glad I didn't though
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Old 08 January 2009, 23:55   #18
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@TC
Now the big question is if it is 'it'

@DH
Good you left the tweezers bit out mate
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Old 08 January 2009, 23:57   #19
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@DH

It's poetry just as it is my friend............Perfect.

Serious though we need to find a schematic of the audio circuit for our friend Molcos here, Having studied the piccies I don't think they have been replaced though as all components are still aligned up perfectly.
I think Mr Drunk just resoldered them hoping they may have been bad contacts.

Change those caps defnitely, perfect starting point & lets take it from there, If you don't have SMD type use normal electrolytics for now.

TC

I'll try & scan the audio circuit schematic for you tomorrow morning & upload it to the zone for you

Last edited by TheCorfiot; 09 January 2009 at 00:06.
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Old 09 January 2009, 00:07   #20
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And I wasn't even trying to be funny. Just glad I can put a smile on peoples faces and make them ROTFL without even realising it.

Serious Mode:
There is so much flux on the mobo he must of had more than one go at this soldering job whichever way he did it. I would presume he's burnt the poor components out or even damaged the mobo, christ what was he using for solder, solder bars like these and a huge tub of flux



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