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Discussion Starter #1
I'm having a hard time finding good information about the caps needed. This is what I was able to identify from looking at the board. and ordered from Digikey in case anyone else needs to do the repair. I don't know if all the caps are needed, a few posts I found on the web only talk about 6-9 cap. There are 3 I cant identify. I'll try to when I'm changing out.

My sub will occasionally hum at 120hz I think, and I can often get it to stop by turning on and off my lights in the room. I can also turn down the crossover (left at 120 and my receiver does filtering) or turn down the volume to reduce the hum. Turning down volume all the way completely eliminates hum, but also eliminates sound. The caps all look original. All the original caps were 85 degree caps, I upgraded to 105 degree 5000 hour caps. I would appreciate any tips from someone who has done this before.


A couple things I did was reflow solder and it stopped humming for a few days then came back.
I had 2 2200uF 25V caps around in good shape, so I replaced them and it stopped for a few hours then came back, but the hum seems much quieter now so I think I'm on the right track.

# Quantity Part Number Manufacturer Part Number Description Customer Reference Backorder Unit Price Extended Price
1 3 493-11771-1-ND UPW1E471MPD1TD CAP ALUM 470UF 20% 25V RADIAL 0 0.51000 1.53
2 1 493-11716-1-ND UPM1E221MPD6TD CAP ALUM 220UF 20% 25V RADIAL 0 0.44000 0.44
3 28 493-16343-ND UPV1H4R7MFD CAP ALUM 4.7UF 20% 50V RADIAL 0 0.32600 9.13
4 2 493-8131-ND LGG2D152MELA50 CAP ALUM 1500UF 20% 200V SNAP 0 7.94000 15.88
5 4 493-11717-1-ND UPW1C471MPD1TD CAP ALUM 470UF 20% 16V RADIAL 0 0.45000 1.80
6 4 493-11717-1-ND UPW1C471MPD1TD CAP ALUM 470UF 20% 16V RADIAL 0 0.45000 1.80
7 2 493-11108-ND UPJ2E470MHD CAP ALUM 47UF 20% 250V RADIAL 0 1.66000 3.32
8 2 493-16342-ND UPV1E101MGD CAP ALUM 100UF 20% 25V RADIAL 0 0.51000 1.02
9 1 493-11756-1-ND UPV1E470MGD1TD CAP ALUM 47UF 20% 25V RADIAL 0 0.48000 0.48
10 4 493-1832-ND UPW1E102MPD6 CAP ALUM 1000UF 20% 25V RADIAL 0 0.83000 3.32
11 2 493-7340-ND UPM1E222MHD CAP ALUM 2200UF 20% 25V RADIAL 0 1.63000 3.26
12 10 493-3280-ND UTT1H2R2MDD CAP ALUM 2.2UF 20% 50V RADIAL 0 0.30800 3.08
 

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Hey there, allow me to take a stab at this. I believe your gun issues have nothing to do with the type of caps you are using in the sub amp plate, and everything to do with your electrical outlet and ground hum. I am a Carver (3 TFM’s & 3 PM’s) and Sunfire (True Sig 12) owner and fan, and I know that the Sunfire subs are very suscetible to ground hum.

My initial remedy was to purchase an Ebtech Hum X ground loop hum exterminator (on the AC line), and that seemed to work for the most part although the ground hum did creep back in from time to time when someone switched on specific lights in the house.

I also tried the Ebtech HE-2 signal hum eliminator with mixed results. Again had some occasional hum with house lights on, specially 2nd floor bedroom / bathroom lights.

The eventual solution was rather simple but involved some electrical work. I run no less than 5 rack mount power conditioners in my 3 racks of gear. As a test, I ran an extension cord from one of the conditioner outlets to the sub, tried it for a few days and hum was gone for good. Since I had an AC outlet next to the sub, I was just plugging it in there. When I had done some basement renos, I decided to run dedicated lines from the conditioner to the wall, one in front and one in back. I used standard 14/2 wiring up to the conditioner, and then a metal box to covert to soft copper and an AC plug into the conditioner.

With the sub on the conditioner, it was sharing the same ground as the source equipment, and using the same power conditioning as the rest of the gear. That solved the issue.

My recommendation to you, next time someone turns on the lights upstairs and the hum starts, find out which light it is to be able to replicate the issue. Then try to put the sub, via extension cord, on the same circuit as your source gear.

Another option is to unplug all of your source gear and then plug them in one at a time, that might isolate a problematic piece too.

Another test is to wiggle the audio connections, sometimes one of the RCA jacks have a loose solder joint, and you can find it that way, repair the loose jack and hum gone. Also try different cables going to the sub, could be a faulty cable too.

But my money is on the AC outlet not being grounded on the same circuit as your source gear, and sadly, the Sunfire does not play nice when that is the case.
 

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Ground loop can come through at 60Hz, 120Hz or other harmonics (multiples) of 60, as neils says. But it's absolutely possible for a bad capacitor to cause this. Does the problem happen with any cables except power disconnected from the sub? If so, it probably actually is a capacitor.

OP what kind of tips are you looking for? Soldering tips (my main comments on soldering are to get a good soldering iron and good solder and to first add new solder to things before you desolder them as it will help melt the old solder)? Tips on diagnosing specifically which capacitor is bad (use an ESR meter if you want to do this)? Are you asking if we know if you will need any other capacitors? I have no idea; you'll need to look at the board yourself. Capacitors are typically well labeled. Typically only electrolytics and tantalum (a specialized type of electrolytic that is rarely used in modern equipment and is often yellow or blue and teardrop-shaped) fail. Sometimes ceramic caps fail by physically cracking.

You say you reflowed it and it stopped - what did you do specifically? Do you mean you put the entire board in the oven? Or did you use a soldering iron or hot air soldering station to work on any specific solder joints?
 

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Discussion Starter #4 (Edited)
I used a solder gun to heat up all the cap pins on the underside of the board. Didn't bake the whole amp.

I've tried pretty much every outlet in my room. For a test I used a cheater plug without ground for testing and that didn't help.

Hum also stops if I remove the input from the sub when there is hum going on. I later noticed one night when I turned on the light so I can go unplug the sub the hum stopped so I do that now. Sometimes it takes a few tries. It's actually the same light in the room, on the same circuit. I suppose I can get a really long extension cord to try outlets on different circuits.

The hum can happen any time, sometimes I wake up or come home to a humming sub. System was not on while I was gone. At least to the best of my knowledge, no one was home or I was the only one home. Watching a movie will pretty much start it humming. I don't think it's anyone turning on the lights, as everyone is usually with me when I watch movies, or I'm home alone. Now it could be something that turns on by it self, like the fridge compressor... but seems to be too frequent when I'm watching movies.

I've had the sub for several years, and it has only started humming recently. The sub was originally plugged into the same power strip with all the equipment. After it started huming I relocated the sub trying different outlets and getting it closer to me to unplug easier.

I also got a wireless kit once to remove the direct connection between the reciever and the sub. There was no change in huming, I could also stop the hum by unplugging the rca to the sub from the wireless reciever. Cant remember if unplugging the power worked.


I have not tried leaving the sub only connected to power as it most frequently starts huming when I start watching a movie. That causes it the most, and can happen as little as every few minutes, but usually never longer than 30 minutes to start. I've recently also changed recievers to get Atmos, and for a while I had very little equipment hooked up with cables, however everything was still pluged into power outlets. Reciever change had no effect on hum. I've also changed TV's 2 recently upgrading to 4k, but the hum started well before the tv change, and still happens after.


Any tips to help solve would be appericated, I think I have the sodering and desoldering down. I did find a youtube video on removing caps and added a little extra solder to help me decoder, so tips like this is really great! Also I like to understand what people mean when they say the changed "all" the caps. A list of caps would also be helpful, I identified them as well as I can, but some were really hard to read so I could be wrong.


4 caps I cant identify are C20, C3, C9, and C52.

I used my tester on the mounted components and found higher ESR values
 

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Parallel capacitors increase capacitance. If you read lower and it's in parallel with other caps then that's even worse.
 

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Discussion Starter #6 (Edited)
My order of caps arrived. The sub did start huming for frequent a couple days ago. I replaced the 4 1000uf 25v ones today. All the old ones were around 900uf on my meter and the esr was measured at .08 and .09. Chart shows .1 to be bad. I was reading up and didn't find that esr changes with temp, not sure how that effects operation. I also replaced the 2200uf 25v ones with the brand new ones.

The 1500 uF 200V caps are a lot smaller, I didnt put them in yet since I'm not sure if they are right.


I was also going to replace the other, but when I check after removing the caps were well in spec. I didnt check all of them. Think I'll wait and see if the hum returns.
 

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Bumping this post...did changing the Caps permanently fix the issue? I seem to only get hum after an intense movie scene when the sub is really active. They’ll be a hum from that point on.

Used to be worse until I used a power conditioner. That made it much less noticeable
 
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