RT3000P Amp Hums with Photos
dhoya76
Posts: 4
One of my RT3000P bases hums when plugged in. I took out the amp. The caps seem fine (no?) but the black gunk from the factory and the brown stuff on the board are concerning at first glance. Is that normal? Maybe it has heated up over the years and become conductive? 
Comments
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What looks concerning is the bulging/dented 15000uF cap.
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Yeah, I wondered whether the slight bulge was a problem. By “dent” do you mean the vertical scratch on the side or the area on the top around the perimeter? Was hoping the scratch was just aesthetic. Thanks for the input!
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It's toast. No electrolytic cap should have a bulge or dents. If there are two of them change them both.Yeah, I wondered whether the slight bulge was a problem. By “dent” do you mean the vertical scratch on the side or the area on the top around the perimeter? Was hoping the scratch was just aesthetic. Thanks for the input! -
Thanks! I’ll replace both and maybe go ahead and recap the working amp, too. Do you think that black sealant gunk and brown resin residue on the board are probably normal even if messy looking? I’ll take out the working amp tonight and do a comparison. Thanks again!
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Thanks! I’ll replace both and maybe go ahead and recap the working amp, too. Do you think that black sealant gunk and brown resin residue on the board are probably normal even if messy looking? I’ll take out the working amp tonight and do a comparison. Thanks again!
All the glue looks normal to me. -
Yeah, I wondered whether the slight bulge was a problem. By “dent” do you mean the vertical scratch on the side or the area on the top around the perimeter? Was hoping the scratch was just aesthetic. Thanks for the input!
Even if the capacitor didn't have a scratch and some damage, if I were you I would replace both of them just because of the heat they get exposed to next to that heat sink. This layout is almost as bad as my blue sound node 2 layout. -
Yeah, I wondered whether the slight bulge was a problem. By “dent” do you mean the vertical scratch on the side or the area on the top around the perimeter? Was hoping the scratch was just aesthetic. Thanks for the input!
Even if the capacitor didn't have a scratch and some damage, if I were you I would replace both of them just because of the heat they get exposed to next to that heat sink. This layout is almost as bad as my blue sound node 2 layout.
Valid concern. I do not know how hot the heat sink actually gets. That being said if you can find caps rated at 105c that could be good insurance. If not 85c lasted this long so, cannot argue that. -
I took out the amp from the “good” RT3000P base, the one that works and doesn’t hum, and it (a) had the same black factory sealant and amber residue (flux?) (although it looked cleaner) and (b) not only had caps with a slight bulge but one of them was leaking a rusty color at the top. So it looks worse but “works.” Haha. I ordered 10 15000uf, 63V, 105 degree caps this morning. They are Chemi-Con. 35x65mm (slightly taller than the std 50mm ones but I measured and still have at least .50 inch of clearance). Despite both looking bad while one hums loudly while the other (worse looking) one doesn’t hum, is it still likely the two caps? I plan to recap both, and have some spares. Thanks!
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Try some denatured alcohol to remove the glue at the bottom of those caps. it should help to release the glue or soften it up to make it easier for you to peel off.
Those caps should be power supply filtering caps, it is a good place to start. While I cannot hear your hum, a 60hz hum is very likely when they go bad. -
If you haven't already eliminated the possibility of a new ground loop hum, you could try swapping the speakers with each other to see if the hum occurs in the same speaker when it's connected to power in the other speaker's location.
Looks like the speaker amps could do with a refresh regardless after being in service for 20+ years.
