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Marantz SR7500 Humming/Buzzing noise (1 Viewer)

prochargedls2

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Recently I bought this receiver off of craigslist, now I normally wouldn't do this at all without listening to them, but considering I spent 20 bucks I'm perfectly happy.

My problem is that whenever there is no input going into the receiver I hear a humming or buzzing sound that's roughly 60hz. It's there when there is no input on and when I plug digital in the buzz gets louder. It's there with any input and no input at all.

I already knew a very small about fixing some receiver problems and my first thought was that it was just a bad capacitor. Easy fix maybe 5 dollars since I don't need to buy a soldering kit. When I got to the guys house I asked what's wrong with it and he said capacitor. Awesome.

When I got back home I popped the top off and on top of it being incredibly dusty, I noticed one bulged capacitor. So only one of them is bad, which from my reading is most likely the cause of this issue.

So my question is where do I buy a replacement capacitor?
free picture upload it is the last capacitor on the left if you're looking from the back in this picture.

Also, I was reading up and I saw a blog on replacing certain caps. and you can get better sound?

Thanks in advance.
 

David Willow

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Try MCM Electronics.


Before you replace anything, try it in a different outlet in a different part of the house (try it in someone else's house if you can) to rule out some other issue with your power (ground loop or some electric motor causing the hum).
 

Jason Charlton

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Radio Shack (if there's one still open in your area) usually has a decent selection of caps and other electronic components - they're usually found in thin flat drawers along with resistors, diodes, etc.


As far as "getting better sound" by replacing certain caps... I doubt the validity of that claim. Most of "how a system sounds" is a function of the speakers, not the receiver. The best way to improve how a system sounds is to use good speakers - or to put it another way: a top of the line receiver paired with crappy speakers will still sound crappy, but really nice and efficient speakers will sound excellent even with a modest entry-level receiver behind them.
 

Jason Charlton

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You need either the schematics for the receiver, which would clearly indicate the specs of the cap, or you need to closely examine the cap that's there and hope it has the necessary params clearly labeled on the outside (desolder it from the board if necessary so you can more easily read the sides).
 

prochargedls2

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Yeah I have the specs for which one I need, but on that site there are multiple ones with those specs. Should I just buy the one with the highest temperature range? One has 85C he other has 105C


What I need is 35v 2200uF, which is easy but again I don't know which one with that specification to buy.
 

Jason Charlton

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Also, I would add that if you are able to remove the capacitor, you are probably much better off taking the physical capacitor to a local electronics parts supplier and have them help you pick the correct replacement, than ordering online.


I've done some printed circuit board repairs for my other hobby, restoring old pinball machines. There have been several cases where two capacitors (or other component) that have matching specs are drastically different in size. It's very easy to order the wrong part. Buying in person will help reduce this likelihood.
 

Jason Charlton

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prochargedls2 said:
Yeah I have the specs for which one I need, but on that site there are multiple ones with those specs. Should I just buy the one with the highest temperature range? One has 85C he other has 105C


What I need is 35v 2200uF, which is easy but again I don't know which one with that specification to buy.

If the temp tolerance is the only variable, then yes, I would go with the higher tolerance for heat.
 

prochargedls2

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Well I hit up Radio Shack and they only had axial caps for those specs, no radial. And there are no other stores that sell this stuff near me.
 

Jason Charlton

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Bummer... but at least it sounds like you've got a decent handle on this. In the end, it's a $20 receiver and a dollar and change for the cap, so it's not like you'll be out a whole lot if it doesn't do the trick.


Whatever happens, keep us posted and report back your experience. I'm curious to see what sort of results you have.
 

prochargedls2

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Haha yep. I have quite a bit of experience with auto electrical, soldering caps, transistors, etc to the computers so I can't imagine this being much different.


I hooked up it even with the bad cap. and plugged my HD598's into it and my first reaction was ****! I am coming from a Harmon/Kardon AVR 225 receiver which was pretty nice IMO, but this SR7500's sound was so clean and crisp. I wasn't expecting it to make this big an impact on just headphones. Can't wait to hook it up to my speakers with everything *hopefully* working properly.


Any idea how much these receivers still go for? MSRP is $1000 but that's ridiculous, so I have no idea how much they're really worth in case I want to sell it.


The guy I bought it from told me his dad upgraded to a Mcintosh receiver and was going to throw this SR7500 out, which was probably why the price was so low (20 bucks after a little haggling of course)
 

prochargedls2

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After a long wait I got the capacitor in the mail yesterday. Unsoldered the old one, popped the new one in. After some trial and error of forgetting to plug a few cables in I finally got them all hooked up and sound was made! The sound is superb, had no idea that it would sound this much better. Only complaint is that I can't change Bass/Treble settings when headphones are plugged in.


I can post pictures if desired, but I don't think that many people have taken interest in this. THanks for all the help!
 

prochargedls2

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Thanks! Figured out how to adjust the tone with headphones. I find this so hard to believe that a receiver upgrade changed the sound night and day.


Thanks for all the help!
 

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