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Post by jazzdad on Nov 21, 2023 11:30:13 GMT
Hi all,
I hope one of you DIY experts can help me! I have a Parasound A21 and I want to replace the 4 x 22000uf 100v screw in power caps.
I have the replacements, but can't for the life of me understand how to access the caps on the board. The terminals are facing down, however the transformer is screw fixed to the bottom of the chassis along with a bolt.
Do I have to completely remove the transformer to remove the bottom chassis to replace the caps?
I did request a service manual from Parasound but was denied.
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Post by electronumpty on Nov 21, 2023 12:16:21 GMT
Best if you post a few photos! Be easier to see what you are talking about.
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Post by jazzdad on Nov 21, 2023 13:39:34 GMT
Best if you post a few photos! Be easier to see what you are talking about. I have the pics but can't see an option to upload them? |
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Post by macca on Nov 21, 2023 13:50:09 GMT
save the photo on your hard drive Go here and upload it imgbb.com/copy the 'BBC' code it gives you Paste the code into your post here. |
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Post by jazzdad on Nov 21, 2023 13:56:22 GMT
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Post by brucew268 on Nov 21, 2023 14:06:04 GMT
It looks as though the transformer can stay but the PCB needs to be removed and probably all the semiconductors unscrewed from the heatsinks on the sides. Then proper heatsink paste used when they are re-attached. Unless there's something more clever going on with the central capacitor clamps.
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Post by brucew268 on Nov 21, 2023 14:09:32 GMT
Might be that the common bar that all the actives are screwed to will unmount neatly from the external heatsinks which would make that a lot simpler.
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Post by jazzdad on Nov 21, 2023 14:16:52 GMT
So you think the central screw holding all 4 caps in the clamp will release them all? Not sure if I've understood
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Post by brucew268 on Nov 21, 2023 14:42:29 GMT
So you think the central screw holding all 4 caps in the clamp will release them all? Not sure if I've understood That would be really clever but can't imagine how it would provide a good secure electrical contact if the release was that easy. Might be that the common bar that all the actives are screwed to will unmount neatly from the external heatsinks which would make that a lot simpler. This refers to the semi-conductors mounted to the heatsinks at the sides. |
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optical
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Post by optical on Nov 21, 2023 14:48:29 GMT
Looks like you'll have to deconstruct the case (as others correctly suggested) to gain access to the tags from the caps where they meet the board.
Doesn't make for particulary straight forward re-capping, but at some point the main board and case will have to be apart.
Those clamps around the caps currently are likely just to hold them in place and keep their proximity from each other and other components.
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Bigman80
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Post by Bigman80 on Nov 21, 2023 15:11:01 GMT
It always seems like such a great idea to have everything on one PCB....then when you need to get to someone, just one cap...the whole shebang has to come out. What a pain In the arse. My advice, give firebottle a shout and get the forum pro on the job. Side note...kudos to Parasound, as that Idea to have the bridge rectifiers coming through the PCB was the way I originally designed the PCB for the AVALON power amp modules. I'd bever seen anyone do it before, but I now sit in awe of the design team. That's really great to see. |
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Post by jazzdad on Nov 21, 2023 15:59:52 GMT
It always seems like such a great idea to have everything on one PCB....then when you need to get to someone, just one cap...the whole shebang has to come out. What a pain In the arse. My advice, give firebottle a shout and get the forum pro on the job. Side note...kudos to Parasound, as that Idea to have the bridge rectifiers coming through the PCB was the way I originally designed the PCB for the AVALON power amp modules. I'd bever seen anyone do it before, but I now sit in awe of the design team. That's really great to see. This is definitely out of my comfort zone then. I was naive to think I could simply unscrew the caps and replace them in 5 mins! Maybe by some luck there's someone in this forum in the Essex area who can do this for a fee? |
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Bigman80
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Post by Bigman80 on Nov 21, 2023 16:21:30 GMT
I don't think we have anyone on this forum in Essex and to be honest, and that's not a 10 minute job.
Alan (Firebottle) is based in the west Midlands and is very fair with his pricing. He's done a lot of work for everyone it seems, so drop him a message.
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Post by jazzdad on Nov 21, 2023 16:39:55 GMT
Thanks bigman80 and for everyone else's input it's much appreciated. Definitely not a 10 min job but willing to pay whatever it takes to have to them replaced. There's a place called Essex amp repairs who I'll try in the first instance. Failing that I'll contact the man firebottle 👍
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Post by firebottle on Nov 21, 2023 20:52:41 GMT
Yes getting a single PCB out can be a ball ache. Worse still is when the design doesn't allow any testing without reinstalling the PCB.
I have come across this and it is very frustrating.
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Post by phonomac on Nov 22, 2023 9:07:48 GMT
jazzdad Why do you want to replace them?
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Post by jazzdad on Nov 22, 2023 11:16:12 GMT
jazzdad Why do you want to replace them? I think the amp is 2007 or older and Iit's on at least 12 hours a day. I feel as though the bottom end is a little soft and there's also some 60hz hum through the sub using speaker level inputs (this could be a different issue though). I just feel like it's time they were replaced. No immediate sign of visible failure although I can't see around the terminals |
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optical
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Post by optical on Nov 22, 2023 12:26:05 GMT
jazzdad Why do you want to replace them? I think the amp is 2007 or older and Iit's on at least 12 hours a day. I feel as though the bottom end is a little soft and there's also some 60hz hum through the sub using speaker level inputs (this could be a different issue though). I just feel like it's time they were replaced. No immediate sign of visible failure although I can't see around the terminals That's some heavy usage to be fair, sounds like it is more than ripe for a recap. |
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Post by macca on Nov 22, 2023 18:14:05 GMT
I doubt very much they need replacing. If it was a quick job then why not but they are very unlikely to be the cause of your dissatisfaction.
The hum will be a ground loop.
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Bigman80
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Post by Bigman80 on Nov 22, 2023 23:03:11 GMT
The hum will be a ground loop. It may not be a ground loop, but caps rarely (if ever) hum when they need replacing. Usually cause horrible distortion or a very disconcerting buzzing noise. |
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Post by jazzdad on Nov 23, 2023 11:52:06 GMT
The hum will be a ground loop. It may not be a ground loop, but caps rarely (if ever) hum when they need replacing. Usually cause horrible distortion or a very disconcerting buzzing noise. The hum only happens when the sub is around -20db volume and above. I've spoken to the manufacturer and tried a few things which made no difference. They said it's 60hz interference through the cable which is probably unlikely as I'm using mogami 3103 which is heavily shielded. That is another story though. The cap replacement could just be paranoia due to their age and wondering if I've lost anything sonically. They're definitely past their rated time span |
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Bigman80
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Post by Bigman80 on Nov 23, 2023 12:00:25 GMT
It may not be a ground loop, but caps rarely (if ever) hum when they need replacing. Usually cause horrible distortion or a very disconcerting buzzing noise. The hum only happens when the sub is around -20db volume and above. I've spoken to the manufacturer and tried a few things which made no difference. They said it's 60hz interference through the cable which is probably unlikely as I'm using mogami 3103 which is heavily shielded. That is another story though. The cap replacement could just be paranoia due to their age and wondering if I've lost anything sonically. They're definitely past their rated time span What's your source? |
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Post by jazzdad on Nov 23, 2023 13:25:18 GMT
The hum only happens when the sub is around -20db volume and above. I've spoken to the manufacturer and tried a few things which made no difference. They said it's 60hz interference through the cable which is probably unlikely as I'm using mogami 3103 which is heavily shielded. That is another story though. The cap replacement could just be paranoia due to their age and wondering if I've lost anything sonically. They're definitely past their rated time span What's your source? The A21 is being fed by an Audio Research LS26. The 2 power caps had actually failed in that a while back and were replaced. |
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Bigman80
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Post by Bigman80 on Nov 23, 2023 13:26:16 GMT
The A21 is being fed by an Audio Research LS26. The 2 power caps had actually failed in that a while back and were replaced. Ah, no....digital or vinyl front end? |
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Post by jazzdad on Nov 23, 2023 14:26:31 GMT
The A21 is being fed by an Audio Research LS26. The 2 power caps had actually failed in that a while back and were replaced. Ah, no....digital or vinyl front end? Ah sorry! Digital mainly, Quobuz via an SoTM sm200 streamer. Also vinyl but not as much. |
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Bigman80
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Post by Bigman80 on Nov 23, 2023 14:30:34 GMT
Ah, no....digital or vinyl front end? Ah sorry! Digital mainly, Quobuz via an SoTM sm200 streamer. Also vinyl but not as much. Is the interference happening with both sources? |
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Post by jazzdad on Nov 23, 2023 16:59:45 GMT
Ah sorry! Digital mainly, Quobuz via an SoTM sm200 streamer. Also vinyl but not as much. Is the interference happening with both sources? Yes, also the TV is linked up to the same DAC as the SM200 and hum is still there with that |
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Bigman80
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Post by Bigman80 on Nov 23, 2023 18:14:46 GMT
Is the interference happening with both sources? Yes, also the TV is linked up to the same DAC as the SM200 and hum is still there with that Is the hum there when you switch the sub off? |
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Post by jazzdad on Nov 23, 2023 19:01:05 GMT
Yes, also the TV is linked up to the same DAC as the SM200 and hum is still there with that Is the hum there when you switch the sub off? Nope only when on and is audible only at a certain volume. Tried 2 different plug outlets but still no good |
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Bigman80
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Post by Bigman80 on Nov 23, 2023 19:11:54 GMT
Is the hum there when you switch the sub off? Nope only when on and is audible only at a certain volume. Tried 2 different plug outlets but still no good Hmmm, not sure then. Could be a ground loop as Macca suggested... |
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