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Old 08 October 2016, 02:12   #1
PortuguesePilot
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Amiga sound output is mono (RCA)

Hey.

First, a little background:
I recently bought a really cheap Amiga 600 from a guy who had it stored in his garage for over a decade. The fact that it was so cheap came with its own consequences, though. Some I could see right away, like the HUGE amount of dirt that was over it. After that was wiped off, it was still dirty and unkempt. I never had a 600 before and the price was really cheap (20€) so I bought it anyway. When I came home I cleaned it up nicely and it started to look like an Amiga again with surprisingly little yellowing (it was stored under a plastic canvas which shielded it from the sunlight). However, the case supports were ALL broken and the disk drive didn't work. I had to plug it to one of my surplus power supplies and bought new cables, since the old owner didn't know where his ones were. After I replaced the floppy drive with one of my surplus ones, I loaded a few games and noticed further problems: the keyboard is dead. Not a single key works. I'm not sure if it's the membranes, the connections or even the mainboard itself. Also - and honestly this is what bugs me the most - the sound output is monoural. Can't say for sure if it's the left channel or the right channel that is dead, because I get the same sound output REGARDLESS of what jack I connect to the Amiga.

I'm afraid this might be due to some capacitor or something, but I inspected the mainboard carefully and there's no visible leakage. Every circuit seems to be fine (it's an A300 v1.0 "June Bug" board with no upgrades). The connectors of the keyboard's main plug seem to be worn (as if they have been connected and disconnected a lot of times, making me suspect that this is an old problem, not a new one), so that's probably what's leaving it dead.

Now the plea for help:
Does any of you know what can be the case for this monoural output? Is this a usual or replicable symptom? What can be the cause of this? Is there an "easy fix"?

Also, the keyboard: can it be the connector? Or may it be the socket/board itself? Should I invest in a second-hand keyboard?

Any help is appreciated. Thanks.
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Old 08 October 2016, 02:19   #2
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Quote:
Originally Posted by PortuguesePilot View Post
Hey.

First, a little background:
I recently bought a really cheap Amiga 600 from a guy who had it stored in his garage for over a decade. The fact that it was so cheap came with its own consequences, though. Some I could see right away, like the HUGE amount of dirt that was over it. After that was wiped off, it was still dirty and unkempt. I never had a 600 before and the price was really cheap (20€) so I bought it anyway. When I came home I cleaned it up nicely and it started to look like an Amiga again with surprisingly little yellowing (it was stored under a plastic canvas which shielded it from the sunlight). However, the case supports were ALL broken and the disk drive didn't work. I had to plug it to one of my surplus power supplies and bought new cables, since the old owner didn't know where his ones were. After I replaced the floppy drive with one of my surplus ones, I loaded a few games and noticed further problems: the keyboard is dead. Not a single key works. I'm not sure if it's the membranes, the connections or even the mainboard itself. Also - and honestly this is what bugs me the most - the sound output is monoural. Can't say for sure if it's the left channel or the right channel that is dead, because I get the same sound output REGARDLESS of what jack I connect to the Amiga.

I'm afraid this might be due to some capacitor or something, but I inspected the mainboard carefully and there's no visible leakage. Every circuit seems to be fine (it's an A300 v1.0 "June Bug" board with no upgrades). The connectors of the keyboard's main plug seem to be worn (as if they have been connected and disconnected a lot of times, making me suspect that this is an old problem, not a new one), so that's probably what's leaving it dead.

Now the plea for help:
Does any of you know what can be the case for this monoural output? Is this a usual or replicable symptom? What can be the cause of this? Is there an "easy fix"?

Also, the keyboard: can it be the connector? Or may it be the socket/board itself? Should I invest in a second-hand keyboard?

Any help is appreciated. Thanks.
For sound issue, what happens if you swap leads around, does the issue switch channels? Other than that it will more than likely be a cap issue.

On keyboard, you could try trimming 2mm off the bottom of cable. So it makes contact against a non used part of carbon.
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Old 08 October 2016, 02:27   #3
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Thanks for replying, FOL.

Quote:
Originally Posted by FOL View Post
For sound issue, what happens if you swap leads around, does the issue switch channels? Other than that it will more than likely be a cap issue.
Whatever cable I connect, I get the same sound output. If I connect both audio cables, one cable (regardless of it being the right one of the left one, or the left in the right or the right in the left, etc...). It always plays the same channel, which makes me think that maybe one of the audio capacitors is dead or maybe - God forbid - Paula itself is faulty. But I honestly don't know, hence my cry for help.

Quote:
Originally Posted by FOL View Post
On keyboard, you could try trimming 2mm off the bottom of cable. So it makes contact against a non used part of carbon.
Thought about that, but I'm unsure if I should. The cable itself is already quite short and it's easy to strip it away from the socket, even with it clipped. As I said before, the Amiga was in very bad shape, with all the case supports broken and even screws missing, which is a very good indicator that this Amiga has been opened quite a few times, which makes me suspect that the keyboard issue is an old one that the previous owner "forgot" to mention (and hence why he was willing to sell it so cheap). I may risk cutting off the bottom of the cable, since I have nothing to lose. If it doesn't work, I may buy a second-hand keyboard (seen them for sale online. They cost more than the whole A600 cost me). And since I'm not sure if the problem is just with the keyboard or in the socket/mainboard itself, it is a risky investment...

Does anyone else has any thoughts or ideas? Thanks.

Last edited by PortuguesePilot; 08 October 2016 at 02:43. Reason: typos fixed
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Old 08 October 2016, 08:44   #4
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I'm afraid this might be due to some capacitor or something, but I inspected the mainboard carefully and there's no visible leakage.
Unless the board is already recapped (which I doubt based on your story) every single (electrolytic) capacitor has leaked already. You may not see it (leaked electrolyte is hiding below the plastic capacitor base plate) but trust me, that is the case. So all bets are off until you have recapped the board (though I fail to see how leaked audio caps would cause the problem you are describing but like said, all bets are off).
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Old 08 October 2016, 14:00   #5
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Don't worry about Paula. Capacitor leakage might have damaged the op-amp which amplifies Paula's sound. That's a cheap part, though.
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Old 08 October 2016, 15:20   #6
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I must find someone to recap my A600, then? Yeah, I figured that much... Usually, how much does a recap cost?
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Old 08 October 2016, 19:04   #7
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Quote:
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I must find someone to recap my A600, then? Yeah, I figured that much... Usually, how much does a recap cost?
Depends on there is any track repair needed I spose.
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Old 08 October 2016, 19:42   #8
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I must find someone to recap my A600, then? Yeah, I figured that much... Usually, how much does a recap cost?
Your problem probably is finding somebody to do the job for you... I would say expect to pay anything between 50 and 100 euros if you find somebody unless the person is doing the job for charity. Then you have second problem; recapping may or may not help. If it does not help, what then? You need somebody who can diagnose the problem etc. It may get expensive...

I mean, 20 euros for A600 is superb deal even if there are issues, but it may get expensive to get everything fixed unless you can do it yourself! If not you may want to consider selling your A600 on eBay. You probably get more than 20e even if you describe all the problems, there are people who can do the re-capping themselves and want to gamble a bit.
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Old 09 October 2016, 01:43   #9
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(...) I mean, 20 euros for A600 is superb deal even if there are issues, but it may get expensive to get everything fixed unless you can do it yourself! If not you may want to consider selling your A600 on eBay. You probably get more than 20e even if you describe all the problems, there are people who can do the re-capping themselves and want to gamble a bit.
If I can't get the problems fixed for under 50€, I will consider selling it. A pity, 'cos I never owned an A600 before and the 20€ deal was something I was quite happy with. Plus, the little bugger is actually kinda cute...
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Old 09 October 2016, 04:33   #10
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I think 50€ is the going price for recaps, and you seem to have additional repair costs on top of that.
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Old 11 October 2016, 09:27   #11
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The caps themselves are not a big cost, around €10 for good quality ones, but if you need to ship the board somewhere and back, and allow for some compensation for the work, you can't realistically get much lower than €50 total. If you have a friend nearby who can do the soldering, then it's cheap.
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Old 11 October 2016, 12:33   #12
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Recapping of these A300 rev 1 boards is also more difficult than the later ones as the pads are closer together and a bit smaller than the later models.
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Old 11 October 2016, 12:59   #13
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Apart from the mono problem being capacitor related, which is not uncommon, it could also be a mechanical issue with one of the RCA connectors or a cold solder joint on one. People tend to wiggle them a lot when connecting/disconnecting a plug, so if one has become loose, this problem could occur. It is easy to see if you remove the MB and wiggle them while looking at the pads underneath.
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Old 11 October 2016, 14:50   #14
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Quote:
Originally Posted by demolition View Post
Apart from the mono problem being capacitor related, which is not uncommon, it could also be a mechanical issue with one of the RCA connectors or a cold solder joint on one. People tend to wiggle them a lot when connecting/disconnecting a plug, so if one has become loose, this problem could occur. It is easy to see if you remove the MB and wiggle them while looking at the pads underneath.
Good point, you can also have the tags of the audio cables not making good contact with socket earth.
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Old 11 October 2016, 21:04   #15
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Apart from the mono problem being capacitor related, which is not uncommon, it could also be a mechanical issue with one of the RCA connectors or a cold solder joint on one. People tend to wiggle them a lot when connecting/disconnecting a plug, so if one has become loose, this problem could occur. It is easy to see if you remove the MB and wiggle them while looking at the pads underneath.
They're both a bit wobbly, but I'm not sure if that's the problem. However, if I ever decide on taking it to some guy (have to find someone who works with Amiga, which on these parts I'm pretty sure will be kinda hard to do) I'll take that possibility to him as well.
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Old 11 October 2016, 21:12   #16
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(have to find someone who works with Amiga, which on these parts I'm pretty sure will be kinda hard to do)
You do not need to find specifically Amiga expert. Anyone who can work with SMD parts should be able to do the job. I know because I did my Amigas myself without any prior Amiga experience but have to say that Amiga 300 (rev 1) was a major pain.

Last edited by jarp; 11 October 2016 at 21:36.
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Old 11 October 2016, 21:34   #17
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You do not need to find specifically Amiga expert. Anyone who can work with SMD parts should be able to do the job.
That could be a problem, I once took my Amiga to an electronics repair person and they did a TERRIBLE job at replacing the SMD caps. It sort of worked, but it was a murder of the motherboard.

Thankfully years later a proper Amiga nut fixed it all by doing it properly.
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Old 12 October 2016, 02:07   #18
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That could be a problem, I once took my Amiga to an electronics repair person and they did a TERRIBLE job at replacing the SMD caps. It sort of worked, but it was a murder of the motherboard.

Thankfully years later a proper Amiga nut fixed it all by doing it properly.
Well, if I'm going to pay (apparently quite a bit) for it, then I want everything to be done as perfectly as possible, hence why it will be difficult to find the right guy. Electro-technical experts are all around the corner, but specific Amiga experts, not so much... I must do a good research. Unfortunately I don't have much free time to do it right now, but soon as I can, I'll go out huntin'...
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Old 12 October 2016, 07:03   #19
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it will be difficult to find the right guy.
Well it wouldn't be hard, there's plenty ine Europe, but you'll have to add shipping costs, yeah. You can't half ass this by not paying what it's worth for the fix, it will always be for the worst. I learned the lesson the hard way, I could have killed my Amiga for good.
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Old 12 October 2016, 07:41   #20
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There isn't really anything Amiga-specific as such in the process. But you do need someone who knows what they are doing with soldering, and will appreciate that the board is old an needs to be handled with care.

I can swap the caps out for you at low cost if you are not in a hurry (meaning, when I have a spare moment) and have a look at the board in general, although I'm entirely on the other side of Europe.
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