Marantz MA500 Capacitors

David_NC

David_NC

Super Member
I have three of these monoblock amps, and apparently this model has known capacitor issues. I can handle finding replacements of the small caps, but there are two 10KuF / 71V filter caps in each amp labeled C801 and C802 that are bulging, and a couple are almost splitting at the top. The issue is their size. I need them to be no more than 2" tall, which is the easy part; the fact that the diameter needs to be 1.2" / 30mm is the hard part.
I have looked on Digikey and Mouser, and caps that narrow that are anywhere near that voltage. The closest is a Cornell Dubilier (https://www.mouser.com/ProductDetai.../380LX103M080A052?qs=9nXXK2icEIzReJqzT8H3GA==) that's 35mm wide. That might work, if there was only one, but there are two side by side. I'll have to measure to verify, but I don't think this will work.
I'm curious as to what others have used in these amps, as they seem to be known for having bad caps from the factory. Some things I've read said that the smaller caps often bulge and leak after 4-5 years due to being underspec for voltage. The small caps in mine look OK, but I haven't done more than a quick look-see. Perhaps the small caps have been replaced, since they are now significantly older than 5 years.
Any ideas, tips, or insight into these amps is appreciated.
These are nice little amps - 125WPC @ 8 ohms, 180 @ 4, and two can be bridged for more power. Here they are before cleanup; I don't recall one having a chip on the front, so that must be something on it.

MA500 x 3.jpg
 
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If they tend to budge, they may be getting too hot also. If possible I would go for a 105° cap. Try looking through the electrolytic caps at Partsconnexion. Whenever I need a certain sized cap or if I can't find one elsewhere, I try them.
They've helped me out with a big tube guitar amp restore not long ago where I was having a hard time finding the value I needed in a certain size and voltage.
Even 100v would be ok to replace that 71v cap.
 
Lavane said:
If they tend to budge, they may be getting too hot also. If possible I would go for a 105° cap. Try looking through the electrolytic caps at Partsconnexion. Whenever I need a certain sized cap or if I can't find one elsewhere, I try them.
They've helped me out with a big tube guitar amp restore not long ago where I was having a hard time finding the value I needed in a certain size and voltage.
Even 100v would be ok to replace that 71v cap.
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This seems to be a nearly impossible cap to find, mostly due to diameter. I did find these: https://www.amazon.com/2pcs-10000uf-35x50mm-Electrolytic-Capacitors-4061/dp/B01JKW8PFA/. I'm concerned that they might be fakes. Unfortunately, Elna's site is sadly lacking in pictures for me to do even the most basic verification. I did come across a couple that would work, but at $90 each, and my needing 6, the amps would be better tossed. If I can make something closer to 35mm diameter work, this will be much easier.
 
They don't look like fakes from the photo. But it is just a photo. I've run across fakes, but the printing was always off. Crooked, uneven color, blury lettering, etc. I won't buy caps from China either. It looks like a Chinese seller.
I personally don't buy caps from Amazon or Ebay. Nothing at Partsconnexion?
 
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Are these the main filter caps? If so maybe you can go up a little in value?
Like 12kuf for even 15kuf. I've upped the filter cap values in a 1060 integrated and 140 power amp. Even in my older model 16 power amp per the service bulletin, 5.5kuf to 65kuf. Hopefully someone that's had experience working on these will chime in about that.
 
Lavane said:
Are these the main filter caps? If so maybe you can go up a little in value?
Like 12kuf for even 15kuf. I've upped the filter cap values in a 1060 integrated and 140 power amp. Even in my older model 16 power amp per the service bulletin, 5.5kuf to 65kuf. Hopefully someone that's had experience working on these will chime in about that.
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Yep, there's two per amp. I'm curious as to how much bigger I can go without getting any larger. If I could go down in voltage, it'd be a non-issue, but that's not gonna happen.
 
 
Honestly, that may be the way to go. There just isn't anything I could find in those measurements. That's a tight space to put caps in. Its Amazon, so you should be able return them if they aren't what they should be.
 
The problem is the space these fit into is pretty cramped. Anything more than around 50mm tall won't fit, and even 35mm dia. Is pushing it.
 

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Lavane said:
The problem is the space these fit into is pretty cramped. Anything more than around 50mm tall won't fit, and even 35mm dia. Is pushing it.
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I'm going to dig into one of the amps this weekend and see the max that will fit. Due to really having so few choices due to the size constraints, I know I'll have to take what I can get, in terms of terminals and spacing. Hopefully, the PCB is laid out in such a way that I'll be able to drill new holes for the terminals, if necessary. Such a pain! ;)
 
Be careful of the plastic mounting bracket for the rear speaker outputs - mine were fragile and I broke two of them.
It is cramped in there, and those filter caps barely f'ing fit. I don't know that we ever positively concluded that the ones I bought many years ago were fake or not - but ya, people were looking at the font and printing on the caps I bought. Those caps did test (using a cheap tester, no real high voltage leakage test) right under 10K so I installed them. The amps have rarely been used, but none have failed.
I don't think you'll get a 35mm cap in there, they are right next to each other. Maybe there's room to drill another hole or two, for 35mm?
Good luck, sorry I can't help more. These small 10K caps are still unobtanium (lol, $90 per? Not for me) apparently.
EDIT: I can't remember if I had the 30 or 35mm caps - maybe I did modify the board (I think I did?).
 
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What about mounting them vertically to the bottom of the chassis with clamps, then run wires to the board? Would there be enough room mounting them like that using those 35mm caps, and even some that were taller?
 
Sometimes you just have to get creative. Recently I re-capped and re-tubed
A Russian made guitar head amp for my son. The filter and voltage doubler caps were a wierd Russian military type. A positive lead sticking out of the center and the Case as ground secured with a nut. These haven't been made for years.
So I had to bore out the holes in the chassis and PCB and use clamps. The values in the voltages I needed were difficult to find. I had to go with 20mm and 25mm caps that I found at Partsconnexion.
 

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If you can post the exact dimensions and how far apart the pins are, I can see if it's possible to get something custom-made. Packing 10k uf 71v into that size is apparently not easy.
 
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