Leaky capacitors need replacement?


These need to be replaced, don't they?  

https://imgur.com/a/hqXty35
shawn3997

Leaky capacitors need replacement?


shawn3997


If those pics are with the amp upside down then yes, as the electrolyte in leaky electrolytic caps doesn’t flow uphill.
Change with the same value and uF and get 105’C temp ones not 85’C.

These top quality Nichicon's will do fine
https://www.mouser.com/ProductDetail/Nichicon/UCY2V330MHD1TO?qs=OZVHsXXMeBXRI0EgBUy4uA%3D%3D

Cheers George
Yes, it's an upside-down photo and I scraped some of the brown off of the top (bottom) already to see where the leak was coming from.  Thanks!

I should add that I opened the amp up because it was making a sputtering noise every once in a while -- would this perhaps be the cause of that?
I can't get to mouser for some reason.  I should not get electrolytic, right?
If you are ordering caps, you might as well order and replace all the electrolytic while you are at it. Also there is never a problem with getting higher voltage or higher temperature caps, in fact it is recommended. Just check the size. You’ll be quite surprised with how much better it’ll sound when you are finished;.
Are you saying to replace the electrolytics with new electrolytics or use something else?  These are right off the AC mains between the IEC plug and the rest of the amp. 

Are the one's in the picture electrolytic or something else?
Are the one's in the picture electrolytic or something else?


Electrolytic.
Minus - sign on black strip down one side of the cap, donating which leg is minus.

Cheers George
On the electrolytic on the boards, I would recommend Panasonic FM, Nichicon KZ or FG or Elna Silmic II.  These caps all perform at a very high level. 
Are you saying to replace the electrolytics with new electrolytics or use something else? These are right off the AC mains between the IEC plug and the rest of the amp.
These parts are being used in the DC Blocker inside the amp.

They should be replaced with the same value and voltage. @timlub has mentioned some nice quality parts to replace yours, which have a tendency to do this long before their time.
I don't know if I can fit those fancy caps in the same spot -- they are rather large!  I probably need to get something the same size so I can run the leads where they need to go (my amp is point-to-point wired).

Aren't electrolytics generally frowned upon for audio use because they leak and have issues with heat?  My understanding is that they are only used because they are physically small for the farads/volts compared to other types. Is this right?
I should add I would be most happy to put something in that might last longer.
I should add I would be most happy to put something in that might last longer.
Just get the Nichicons I linked to for $1.13 each, quality cap and will last longer than you and the next owner will probably keep the amp for anyway.
https://www.mouser.com/ProductDetail/Panasonic/ECA-2VHG330B?qs=sGAEpiMZZMukHu%252BjC5l7YR8X6v1kBION9...
Cheers George
Ok, thanks, will do!  I have a bunch of soldering questions but I will do a lot of research online before I try it out on the amp.  If anyone wants to help out:

1. What can I use for extra hands?  I would say that is 1/2 of all of my soldering problems -- not being able to hold everything together so it doesn't move when I apply the solder and all the used-to-be soldered stuff is now free to move around. 

2. What can I use as heatsinks to keep the heat to the area where I am soldering and not running out to other solder joints through the wires?

3. Is regular boring old solder from a plastic tube good enough or should I go all fancy silver solder?

I guess that's really all the issues.  :D
Try this https://www.quadhands.com/products/quadhands-workbench

I got mine on Amazon, and it has made soldering much easier.
or parts connexion 


Ok, thanks, will do! I have a bunch of soldering questions but I will do a lot of research online before I try it out on the amp. If anyone wants to help out:
Sorry to be blunt Shawn, for you to ask these questions, this job is not for you to do, get someone that is good with soldering, and component id to do it.

Cheers George
Yeah, you're probably right....  I'll check around locally.  I'm not sure anyone actually does gadget repair here anymore that isn't just iPhone battery replacement.  If not I'll have to ship it off and listen to my old stereo again for a while.  Blech.

Anyone want to put out a shout for a great tech just in case I have to ship?
Thanks to everyone for their help, by the way.
Also, I need an axial version of that Nichicon and mouser has gone mental it seems.  I keep getting 403 errors.  Deny me will you... 

atmasphere
9,377 posts
04-25-2021 2:15pm
Are you saying to replace the electrolytics with new electrolytics or use something else? These are right off the AC mains between the IEC plug and the rest of the amp.
These parts are being used in the DC Blocker inside the amp.

They should be replaced with the same value and voltage. @timlub has mentioned some nice quality parts to replace yours, which have a tendency to do this long before their time.


I am not sure what amp this is inside, but the ripple current rating seems a bit low for a power amplifier.


If this is a DC blocker, I question whether the lowest impedance capacitor is the best choice. That means more high frequency noise is passed through.  Thoughts?

I keep getting 403 errors.


Try this it’s the 2nd one
https://www.mouser.com/Search/Refine?Keyword=33uF+350v+105c

Cheers George
It’s a Music Reference RM-10 and he should use the exact value for the replacement. I can't remember the brand that Roger used, we may still have some lying around, but the Nichicon’s pointed out by George are a good choice and should fit inside. They were one of Roger’s favorite capacitors. As for getting someone to put them in any competent local tech can do it.  
If you have some extras I’d love if you could send a few to me.  I may have found one or two local techs who might be able to do the work.
If this is a DC blocker, I question whether the lowest impedance capacitor is the best choice. That means more high frequency noise is passed through. Thoughts?
No- it doesn't work that way. Actually though if this is a DC Blocker as it appears the voltage only need be 16 volts not 350.

@clio09 is associated with service of these amps. Tony, can you confirm that this is the DC Blocker circuit?
From what I can decipher from Roger's schematic (which has a series of iterative changes written in pencil on it), BOM, and notes it is an electrolytic power supply filter capacitor, 33 uF/350V. As I said previously, the OP should replace it with the same value.
iF you are in USA i would suggest shipping this superb amplifier to tech at Brooks Berdan in Monrovia, CA. They are very familiar with Music reference and the tech will look beyond this issue and get amp properly cleaned up from leak.

just my two cents, they take care of my RM-9.

if all this seems a hassle, i need an RM-10... dead or alive...
Mine is alive and well loved here so it's not going anywhere.  :)

It's just a little sputtery so I'll get that fixed sometime soon, hopefully locally so I don't have to mail it.

@clio09 has been super helpful and great to work with!  Thank you.


hello shawn3998.....I'm curious how old is the amp?  My RM10 Mk II is 10 yrs olde now....perhaps I should check under the hood at some point.
The guy I bought it from said it was 3 years old.
Which MkII do you have, the fixed bias version (you set the bias) or the cathode bias version (amp sets the bias)? I ask because all fixed bias MkIIs are well over 3 years old (mine is at least 15) to my knowledge. A cathode bias version may be within that time window.


The guy I bought it from said it was 3 years old.


Looking at how tarnished the solder is, the grey color and cosmetics of the plastic wrap on those caps, and how long they are (much shorter now), and that they’ve already leaked, I’d say more than 3 years old.
Or they were NOS caps of the shelf that were used and not formed, as electrolytics also have a shelf life and need to be re-formed very slowly when new but old.
https://www.youtube.com/watch?v=vA8YksKJSsQ
Boring as bat **** voice on this guy

Cheers George
My gosh, I’m rebuilding 2 amps right now that are 35 and 38 years old, every cap in both amps were in better shape than those. I didn't catch in the thread which amp that you have. I don't think that you'll find most of those caps in what I recommended in the voltages that you'll need. But I would definitely change any caps with the best that I could find and make sure that you get high enough voltage ratings.  Good Luck,  Tim
If it fits check Mouser part # 647-UCS2V330MHD, the difference in size is 16mm diameter versus 12.5mm, but the ripple current is 900mA versus 380mA for the UCY series.
Is it right that those capacitors have a life rating of 10,000 hours? Will I need to change my capacitors again that soon?
Is it right that those capacitors have a life rating of 10,000 hours?
Rated 10,000 hours at 105°C, life of a capacitor doubles for every 10 degree Celsius decrease in temperature, that means the capacitor operating life at 55 °C is 320,000 hours!
If a capacitor rated 10,000 hours at 85°C, its operating life at 55 °C is 80,000 hours.
If this is truly a DC blocking capacitor for a power amplifier, then those capacitors are grossly under-rated for ripple current. That would lead to premature failure.
@imhifan Ah, I see. That is more comforting...

I will see if @clio09 has any of the original capacitors he can send me and if not I’ll buy the Nichicons as suggested and find someone local (if possible) to replace them.
@shawn3997

Just a FWIW, if those caps are used in an application where they are seeing a higher voltage closer to their rated voltage (in the photo it looks like its in a DC Blocker to me, but who knows), I can tell you from experience that those Illinois caps can do that well short of the time you expect of them. Switching to a Nichicon will assure longer life. As @clio09  recommends, replace them with the same value and voltage.
I will see if @clio09 has any of the original capacitors he can send me


Geez! why go that way, they look like old cheap stuff that may need to be formed, because they are so old, and the same thing may happen again.
Just get the better Nichicons I linked to for only a couple of bucks each.

Cheers George
I need to open the amp back up and take some pictures and measurements and I'll post them later.  It's just a matter of what will fit.
OK, here's a bunch of pictures:
Imgur: The magic of the Internet

I have amp #1249, if that means anything regarding how old it is.

The caps needing replacement are around 15-20mm wide and 40-45mm or so long and are axial and connected as show in the pictures (picture #2, at the bottom right, the two grey ones). 

It looks like one side of each capacitor runs to the ground from the AC plug and then goes through the cap and a resistor to what I imagine is the transformer.  The two capacitors are connected together at ground and the two resistors are connected together at the transformer but they don't connect at the tabbed thingy in the middle, which is just a separator.

Can I shove some small radials in there?  Probably.  I have some vertical height to work with but will the leads be long enough to reach where they need to go?  I'm not sure.  That's my concern with radials.

I could also just use a couple of axials of approximately the same size.  I found two on Mouser:

336TTA350M Cornell Dubilier - CDE | Mouser
PEG124UH2330QL1 KEMET | Mouser

Here's detailed specs for the KEMET since no ripple current is listed:   PEG124UH2330QL1 (kemet.com)

It looks like either will fit fine.  Should I order some of these and take them and the amp to a local tech for replacement or are the radials mentioned preferred?

I'm not as in depth about amp building and repairs as others around here, but now that I see this,  I don't see why you couldn't do what you wanted to in the first place and use a decent metalized polypropylene there, say 33uf/400v.  I don't see any reason why a bipolar wouldn't work there.  Since Ralph chimed in here @atmasphere    I would get his expert advice
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