My childhood best friend was killed about 9 years ago. His parents are finally letting go of his things, and they offered me his Polk RTi100 tower speakers. The Polk RTi100 towers are one of a handful of designs from the early 2000s that is a full range 3-way tower with a built-in self-powered subwoofer. This is accomplished with a plate amp integrated into the speaker input panel.
I think they used them for a while, but they've been sitting for at least a few years now. After about 40 hours of driving to their house and back (both they and I have moved in the last 9 years) I got the speakers and set them up.
Before even connecting the banana plugs to my receiver, I went to plug in one of the amplifiers into my surge protector and the subwoofer immediately started intermittently thrumming -- making a sort of honking noise -- almost certainly being over-driven. I disconnected the amplifier quickly. Suspecting the worst I tried the other speaker and it behaves in the same manner.
I had to perform some minor amplifier repair on a different (Infinity) subwoofer amp a few years ago, so I have more than 0 experience with these types of things, but I'm very much an electronics amateur. I was prepared to re-cap the Infinity sub, but it ended up being just a burnt out resistor that had to be replaced. The whole process was much simplified because I was able to find the service manual for that amplifier.
I've had no such luck with finding diagrams of the amplifier in the RTi100 tower speaker.
I was able to pull out the plate amplifier and examine it. There's a bit of darkening on the board where a Mosfet is soldered to the board, but it's by no means burnt or scorched. As far as I can see all the caps and resistors look OK.
To try to get to the bottom of what was going on, I disconnected the subwoofer driver from the amplifier's output leads (to avoid damaging the subwoofer driver) and plugged the amplifier into AC power with the amp sitting outside the speaker. What I discovered is that the transformer seems to be buzzing intermittently in a manner coinciding with how the subwoofer was thrumming.
Video of this behavior:
https://youtu.be/-zIFATqpQvY
Based on this, it would be my guess that the transformer has gone bad. Unfortunately, with both amplifiers having what appears to be the same failure, I can't check the correct output of the transformer, and I'm not seeing any markings that would properly identify it.
The sole sticker says:
54-0100-5900
KSE 0139
But an internet search doesn't seem to turn up anything meaningful with any of those terms.
I'm also reaching out to Polk support, but based on various threads around the internet (many in the 2013-2016 range) it looks like Polk has long since stopped providing repair support for this product.
In my searching I found numerous listings on eBay and the like for repair services for the amplifiers, but I'm super leery of a scam. UPDATE: I looked into this while finishing up the post, and it turns out the eBay seller I found is "electronetix" who seems to be recommended on a few AV forums and has mostly positive feedback on eBay.
Since these speakers are more for sentimental value than practical value, I'd much rather keep the speakers with non-functional amplifiers (they still work as 2-way speakers), than mail someone the plate amps and they just disappear or come back even more broken.
Ideally what I'm looking for is guidance on how to repair these amps myself, perhaps with a service manual, or barring that a recommendation for a reputable repair shop to send these off to.
I guess as a 3rd option I'd be interested in figuring out a way to bypass the built-in amp and power each subwoofer with its own independent amp... but that sounds like a lot more work than I'm probably willing to put in.
Any and all advice would be greatly appreciated. I'd be happy to provide additional photos or videos if requested.
Thanks in advance!
I think they used them for a while, but they've been sitting for at least a few years now. After about 40 hours of driving to their house and back (both they and I have moved in the last 9 years) I got the speakers and set them up.
Before even connecting the banana plugs to my receiver, I went to plug in one of the amplifiers into my surge protector and the subwoofer immediately started intermittently thrumming -- making a sort of honking noise -- almost certainly being over-driven. I disconnected the amplifier quickly. Suspecting the worst I tried the other speaker and it behaves in the same manner.
I had to perform some minor amplifier repair on a different (Infinity) subwoofer amp a few years ago, so I have more than 0 experience with these types of things, but I'm very much an electronics amateur. I was prepared to re-cap the Infinity sub, but it ended up being just a burnt out resistor that had to be replaced. The whole process was much simplified because I was able to find the service manual for that amplifier.
I've had no such luck with finding diagrams of the amplifier in the RTi100 tower speaker.
I was able to pull out the plate amplifier and examine it. There's a bit of darkening on the board where a Mosfet is soldered to the board, but it's by no means burnt or scorched. As far as I can see all the caps and resistors look OK.
To try to get to the bottom of what was going on, I disconnected the subwoofer driver from the amplifier's output leads (to avoid damaging the subwoofer driver) and plugged the amplifier into AC power with the amp sitting outside the speaker. What I discovered is that the transformer seems to be buzzing intermittently in a manner coinciding with how the subwoofer was thrumming.
Video of this behavior:
https://youtu.be/-zIFATqpQvY
Based on this, it would be my guess that the transformer has gone bad. Unfortunately, with both amplifiers having what appears to be the same failure, I can't check the correct output of the transformer, and I'm not seeing any markings that would properly identify it.
The sole sticker says:
54-0100-5900
KSE 0139
But an internet search doesn't seem to turn up anything meaningful with any of those terms.
I'm also reaching out to Polk support, but based on various threads around the internet (many in the 2013-2016 range) it looks like Polk has long since stopped providing repair support for this product.
In my searching I found numerous listings on eBay and the like for repair services for the amplifiers, but I'm super leery of a scam. UPDATE: I looked into this while finishing up the post, and it turns out the eBay seller I found is "electronetix" who seems to be recommended on a few AV forums and has mostly positive feedback on eBay.
Since these speakers are more for sentimental value than practical value, I'd much rather keep the speakers with non-functional amplifiers (they still work as 2-way speakers), than mail someone the plate amps and they just disappear or come back even more broken.
Ideally what I'm looking for is guidance on how to repair these amps myself, perhaps with a service manual, or barring that a recommendation for a reputable repair shop to send these off to.
I guess as a 3rd option I'd be interested in figuring out a way to bypass the built-in amp and power each subwoofer with its own independent amp... but that sounds like a lot more work than I'm probably willing to put in.
Any and all advice would be greatly appreciated. I'd be happy to provide additional photos or videos if requested.
Thanks in advance!
Comment