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Need help choosing right caps for amp
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Author:  mtosh [ 26 Feb 2018, 14:26 ]
Post subject:  Need help choosing right caps for amp

Hello!

I hope this is the right forum to start in...

I'm trying to replace electrolytic capacitors in my home theater amp (Sherbourn 5/1500A) which is a 5 channel monoblock style chassis. I would experience static and occasional audio drop-outs when using it. It's now about 18 years old and from what I found when doing research, replacing caps is an expectation with these amps eventually.

I have it taken apart, but I'm unsure of the best caps for this job. I don't want to throw in 10 new caps and not be sure they are good quality etc. I'm looking for 10000uf 80v snap in 35mm x 55mm 105c

I'm having trouble finding them on Mouser, and ended up seeing quite a few on ebay. Thanks again for any advice!

Author:  Geek [ 26 Feb 2018, 15:03 ]
Post subject:  Re: Need help choosing right caps for amp

Welcome!

HT units are notorious for bad solder joints. I'd start there before recapping it. Also cleaning controls and switches. Speaker relays are also suspect for intermittent channels.

Those "cannonshell" caps can be replaced with smaller ones of correct value and I always use the next voltage up - 100V for the 80V ones for example.

If bracketed, you can make a perfboard adapter and lose the brackets entirely, or just wrap some tape around them.

Tech Tip: Replace the main rectifier with a skookum one whenever you replace PSU caps - the surge from modern, low ESR caps may blow the old rectifier (I found out the hard way).

Cheers!

Author:  mtosh [ 26 Feb 2018, 18:48 ]
Post subject:  Re: Need help choosing right caps for amp

Thanks Geek!

I'm new at this, so I'm assuming bad solder joints are either loose or cracked? I will check that out. I did have a local repair shop check it over and they wanted to replace all 10 caps ($25 per cap) for just the parts! With labor, we were well over $500 US. They couldn't guarantee that this procedure would even fix the issue, it was step 1. This prompted my DIY movement, plus I would love to learn how to replace caps etc.

Author:  Geek [ 27 Feb 2018, 01:06 ]
Post subject:  Re: Need help choosing right caps for amp

Yikes!
I totally recap vintage like Marantz 2275 for that kind of money :hot:

Author:  mtosh [ 27 Feb 2018, 09:17 ]
Post subject:  Re: Need help choosing right caps for amp

If I do replace the caps, what brand(s) would you recommend?

Author:  Geek [ 27 Feb 2018, 14:43 ]
Post subject:  Re: Need help choosing right caps for amp

The electrolytics in the signal path I like to use Silmic-II or Nichicon Fine Gold (UFG), depending on how I want to voice the amp. Bipolars I always use Nichicon Muse UES series.

The small power supply caps and decouplers, Panasonic FC, FM or FR.

The large PSU caps depends on your budget.... United Chemicon are great bang for the buck with their large can series, or for more $, Nichicon LGU, or LLS.

Just my opinion.

Author:  mtosh [ 27 Feb 2018, 22:44 ]
Post subject:  Re: Need help choosing right caps for amp

Thanks, opinions are what I'm looking for. I appreciate it!

Author:  steakhead [ 01 Mar 2018, 11:45 ]
Post subject:  Re: Need help choosing right caps for amp

I suggest you follow the advise you received, I know for a fact from the lessons I
have experienced, that it is good

Author:  gofar99 [ 02 Mar 2018, 22:29 ]
Post subject:  Re: Need help choosing right caps for amp

Hi, Some good advice above. I would suspect the switches, controls and jacks for such noise. My personal experience has been that caps don't normally cause those issues. Something like Deoxit on the suspected controls etc will often restore normal performance. If not you are only out about $10. Then go to connections between boards if they are used in the unit. Then really look over the boards for nice shiny solder connections...depending on your skill level you can retouch any that are suspect. This can be problematic if you don't have the right skills and tools. Caps would be my last thing to try. I have seen too many good pieces of equipment hacked and screwed up in the process. Repairing botched jobs does get costly. I also use Silmic II, Nichicons, and Panasonics.

Good listening
Bruce

Author:  mtosh [ 10 Mar 2018, 21:17 ]
Post subject:  Re: Need help choosing right caps for amp

I took the amp apart and cleaned it out really well with detoxit, most of the solder connections looked really good. Hard to notice any obvious issues. Put it together and hooked it up, seemed to be working well and then after 30 minutes or so one of the speakers began to sound "crackly" and occasionally lose sound completely. If I turned off the amp and back on after a few minutes it would work well again for a while before the static crackles would begin again. Wouldn't always be the same speaker. It was almost as if power would either build up or drain (from the caps?) and begin to cause problems.

I most likely have a ground loop problem as I placed a cheater plug onto the amp and removed a buzzing sound. However, it didn't keep the static crackles from surfacing.

Is it looking like bad caps yet, or possible solder fixes and/or ground loop issues?

Thanks!

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