RT3000p lower unit making audible hum & auto off not working

jdustinb

I have a pair of RT3000p's and both of them make an annoying hum noise when powered on. I've checked audio sources and is constant regardless if there's a source or not, they just need to be powered on. Is this a group loop issue or could it signal failing filter caps? I'm not really familiar with what the filter caps are or do but I've read this elsewhere.

The other issue is that the power switch on one of them doesn't appear to be working as it won't turn off in the off position and it no longer powers off automatically. The only way to turn it off is to unplug the unit. Combined with the hum, this is maddeningly annoying.

Thanks!
Jeff

[Deleted User]

Hello Jeff,
Thanks for posting. It is possible you have an earlier version of the RT3000p bass amplifier and if there is strong radio frequency (RF) in your area it will produce humming. As a test try moving the speaker into another room of your house and see if it is the same.
Regards, Ken

jdustinb

Kenneth Swauger wrote: »

Hello Jeff,
Thanks for posting. It is possible you have an earlier version of the RT3000p bass amplifier and if there is strong radio frequency (RF) in your area it will produce humming. As a test try moving the speaker into another room of your house and see if it is the same.
Regards, Ken

Thanks, Ken - I'll try this either tonight or tomorrow and report back.

jdustinb

The speakers still produce humming in different rooms, even when the speakers are not connected to the receiver. It's not as bad when not connected. There are times where it will pulsate. When connected to the receiver however, it produces a steady hum.

It seems to get worse the longer the units have been on (1-2 hours).

Any thoughts on how to resolve this?

[Deleted User]

Hello,
From your description it sounds as though you have the earlier versions of the bass amplifier. Are these newly acquired speakers or did you have them for a while and move to a new location? The reason I ask is that it is the combination of the amp's design and a high level of ambient RF that causes the humming problem. I'm not sure what options are available through Polk's service center, but give them a call at 1-800-377-7655.
Regards, Ken

jdustinb

Thanks, Ken - I've had these since around 2000 actually, and moved about two years ago. The hum has been present since I moved, don't really recall whether it was an issue before that or not but it was never to the point where I thought much about it. It seems as though it has gotten worse or I've simply noticed it more over the last two months or so where I've been driven to the point where I need to take care of it. Perhaps I'm just getting more picky while getting older.

Thanks for the info though - I'll be sure to give them a call to see what they suggest.

jdustinb

Update - called and they said they'll update the amps for me for a very reasonable cost! Definitely excited. I found a few older threads where it appears others have experienced this in the Seattle area the same. Getting the amps ready to send in.

Thanks again for all the info Ken. Definitely much appreciated as it will quite literally be music to my ears.

Cheers,
Jeff

[Deleted User]

I'm glad they were able to help out, funny how Seattle figures in on this. Many years ago NAP and I were sent out to Seattle to help figure out what might be happening with RT3000p and humming problems. There must be some really strong RF in that area, either that or all the caffeine fumes.
Cheers, Ken

lorderos33

Kenneth Swauger wrote: »

I'm glad they were able to help out, funny how Seattle figures in on this. Many years ago NAP and I were sent out to Seattle to help figure out what might be happening with RT3000p and humming problems. There must be some really strong RF in that area, either that or all the caffeine fumes.
Cheers, Ken

HAHAHAHA, Probably a little of both

adb3da

Hi, just wanted to bump this old thread. I recently acquired a set of RT 3000p and both subs units have a small but steady hum when the amps are on. It's not terribly loud but is noticeable. I called Polk CS and they think it probably needs a recap somewhere and that I could send them in for repair. Some google searching shows this is fairly common on this speaker and I'm just curious to hear how other owners resolved this that have been down this road. I am probably going to send the amps to Polk next week but want to try any other home remedies before I do so. Thanks!

Gatecrasher

How much are they going to charge for the repair? Did they say?

I am in the St. Louis area too and have six RT3000p subs.

adb3da

Gatecrasher wrote: »

How much are they going to charge for the repair? Did they say?

I am in the St. Louis area too and have six RT3000p subs.

The guy estimated about $100 per amp. Plus the shipping, so I am guessing $250 ish? I'm kinda torn because the hum really isn't that bad and is really only noticeable when sound is not being played and the sub amps are still on. After 5 mins or so they turn themselves off. I also noticed that it gets louder as I adjust the crossover dial up so I wonder if it has anything to do with my amp feeding them. I guess I need to experiment some more. But the seller did mention the hum when I picked them up so I don't think it's just my equipment.

You have 6 of these subs???? Your 10.2 system in your sig is crazy! Do you have any pics?

WLDock

I just spent the weekend going through the three amps that I have. Bad caps are generally the culprit but also the older amps do tend to make more noise. Try to plug into the same socket and try an AC ground lifter 2 prong plug adapter

I have two later models and one older one. The older one I bought as a defective used unit but is headed for the trash as traces were burnt, damaged and one board is cracked. Anyway, I finally got the two later version amps working and went through and checked every major component, and replaced the caps, and re-flowed some solder joints. So far so good...was listening to acoustic bass solos this morning.

Anyway, I might consider offering repair service to Polkies for cap replacement ...might be able to save a little money. However, shipping is my concern. If these amps are not packaged correctly they can get beat up and damaged. Anyway, I'm a tech and work around power electronics for a living. The amps are not difficult to pull apart and repair. So, if the amp is working I'm alright with doing the caps and looking it over. If not, there are major things like burnt components, damaged traces, cracked boards, etc. that I would not want to deal with if possible.

Send me a PM if interested.

Walt

adb3da

WLDock wrote: »

I just spent the weekend going through the three amps that I have. Bad caps are generally the culprit but also the older amps do tend to make more noise. Try to plug into the same socket and try an AC ground lifter 2 prong plug adapter

I have two later models and one older one. The older one I bought as a defective used unit but is headed for the trash as traces were burnt, damaged and one board is cracked. Anyway, I finally got the two later version amps working and went through and checked every major component, and replaced the caps, and re-flowed some solder joints. So far so good...was listening to acoustic bass solos this morning.

Anyway, I might consider offering repair service to Polkies for cap replacement ...might be able to save a little money. However, shipping is my concern. If these amps are not packaged correctly they can get beat up and damaged. Anyway, I'm a tech and work around power electronics for a living. The amps are not difficult to pull apart and repair. So, if the amp is working I'm alright with doing the caps and looking it over. If not, there are major things like burnt components, damaged traces, cracked boards, etc. that I would not want to deal with if possible.

Send me a PM if interested.

Walt

Thanks for the info!

I have some questions. I'll send a PM.

adb3da

I guess I should clarify that my hum is heard from the drivers and not from the rear plate of the amp. I don't know for sure if it's the amps that have an issue or the drivers. All four of the drivers produce the same hum so I was thinking the amps were the source of the hum.

WLDock

Troubleshoot for a ground loop by putting all the plugs on the same strip or temporarily lift the grounds.
http://www.audioholics.com/home-theater-connection/ground-loops-eliminating-system-hum-and-buzz

Gatecrasher

I have three pairs of RT3000p speakers and two of the subs are the original (oldest) design that Ken was referring to. You can actually hear radio over them. In between songs or during a quiet period you can hear commercials and music from radio stations. The newer style doesn't seem to have the RFI issue.

The way you can easily tell what type of speakers you have is by the power indicator lamps. The first generation that has the RFI problem has indicator lamps that turn-off when the amplifier auto shut-off is actuated. So in other words, after you turn your receiver off, a few minutes later the amplifiers in the speakers shut-off and the indicator lamps do too.

The newer design still has the auto shut-off feature but the power indicator lamps always stay on as long as they are plugged into the wall.

I was told by Polk that the lamp function was changed to comply with European law which requires an indicator lamp to be on any time something is plugged into a wall outlet. Instead of making two different versions of this feature, Polk supposedly decided to just do it with all of them. At the same time they changed the ground scheme to eliminate the RFI.

Both styles can develop the "hum" though.

I was talking to another guy a while back and he told me there were actually three revisions to the amps but I had never heard that before.

Do your speakers have power indicator lamps that turn-off automatically or are they always on?

adb3da

Gatecrasher wrote: »

I have three pairs of RT3000p speakers and two of the subs are the original (oldest) design that Ken was referring to. You can actually hear radio over them. In between songs or during a quiet period you can hear commercials and music from radio stations. The newer style doesn't seem to have the RFI issue.

The way you can easily tell what type of speakers you have is by the power indicator lamps. The first generation that has the RFI problem has indicator lamps that turn-off when the amplifier auto shut-off is actuated. So in other words, after you turn your receiver off, a few minutes later the amplifiers in the speakers shut-off and the indicator lamps do too.

The newer design still has the auto shut-off feature but the power indicator lamps always stay on as long as they are plugged into the wall.

I was told by Polk that the lamp function was changed to comply with European law which requires an indicator lamp to be on any time something is plugged into a wall outlet. Instead of making two different versions of this feature, Polk supposedly decided to just do it with all of them. At the same time they changed the ground scheme to eliminate the RFI.

Both styles can develop the "hum" though.

I was talking to another guy a while back and he told me there were actually three revisions to the amps but I had never heard that before.

Do your speakers have power indicator lamps that turn-off automatically or are they always on?

My power LEDs turn off when the amps do, so I believe I have an early version of the amp.

My hum is very uniform however, and I cannot hear anything from a radio signal interfering. I really don't know what the cause is. And I should also note that these amps were serviced by the previous owner. The shop that did the repair placed a sticker on the back. I'm not sure of the extent of the service but I know that the two large black capacitors were replaced with a larger cap. They actually had to mod the board because they wouldn't fit into the existing spot on the board. I've come to this conclusion by comparing photos online of the amp to my actual amps. I might try to take a pic and post it on here.

That being said, I don't know if this mod was done properly or not, so maybe that's my issue. Assuming the mod was performed OK then I don't know if the power caps are the root of my issue.

WLDock

Its possible they used a cap that was not a snap in style but one with screws.

RT3016PSE

Hello Nobody said what type of connection they were using (RCA / XLR) or bal with RCA adopter at Sub end.
I read some where that connecting RCA -out(sub) to any free RCA -in (amp) reduces noise.
It was quite possible in the RT manual