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Old 8th November 2013, 12:54 PM   #1
bmoraru is offline bmoraru  Romania
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Default Beefing up old PSU filter caps - advice needed!

On some old equipment I really like -a Dual RC 5900 receiver-- and which I'm intending to revamp, I would like to improve the PSU filter caps (6800uF), but Im wary of removing them, since they appear to be thoroughly glued on to the PCB. So I am considering of adding some new, high-performance low ESR caps in parallel with them and underneath the PCB, hence of a limited physical size.

Would adding some 1000uF worth of high quality caps make a difference? Would it make the circuit more efficient for filtering? I assume it would lower the ESR, right?

Any other thoughts? Thanks a lot!!!
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Old 8th November 2013, 12:56 PM   #2
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Old electrolytics are the most common failure mechanism in old electronics. Get them out and replace them. Even if they are glued to the PCB - do everything to be careful to the PCB and take them out.
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Old 8th November 2013, 01:22 PM   #3
bmoraru is offline bmoraru  Romania
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Quote:
Originally Posted by KatieandDad View Post
Old electrolytics are the most common failure mechanism in old electronics. Get them out and replace them. Even if they are glued to the PCB - do everything to be careful to the PCB and take them out.
ALthough I'm pretty skilled, removing some glued-on caps in equipment that is dear to me is the last option--for now, I am hoping for some improvement by adding some more caps in parallel...
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Old 8th November 2013, 01:27 PM   #4
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Too much capacitance can kill diodes and/or secondary transformer windings due to exceedingly high inrush current, keep that in mind.
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Old 8th November 2013, 01:36 PM   #5
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As Rodeodave states, the inrush current of large caps has to be considered. You could probably parallel them with up to about 4700uF before you might have problems. But I would Dremel out the old ones first.
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Old 8th November 2013, 02:09 PM   #6
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I've never seen a glued in cap that wouldn't succumb to a square ended X-Acto knife blade worked under the glue. You really need to get those out of there because the leads are sealed in a pocket and they can eventually corrode away if the cap leaks a bit.
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Old 8th November 2013, 02:53 PM   #7
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I've done this many times. Please don't keep the old ones... They will for sure cause problems. Use a sharp knife to cut through the glue around the cap. Desolder the old ones using a "sucker" and braid to clean it properly. Use good solder like wbt 0820..

My suggestion is; Elna for audio (ebay) 8200uf and voltage no less then the old ones.
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Old 8th November 2013, 05:32 PM   #8
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Quote:
Originally Posted by bmoraru View Post
ALthough I'm pretty skilled, removing some glued-on caps in equipment that is dear to me is the last option--for now, I am hoping for some improvement by adding some more caps in parallel...
Not a good idea. Don't be a fool. Follow the advice and get them out
before they do harm.


Quote:
Originally Posted by Rodeodave View Post
Too much capacitance can kill diodes and/or secondary transformer windings due to exceedingly high inrush current, keep that in mind.
Dave, stay real. Adding 1000 F to the existing 6.800 F ones certainly
won't kill any diodes.

I'd pull them out and put some decent new 10.000 F in. Work done.
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