Polk Audio RTi100 Plate Amplifier won't power on and intermittently honks and buzzes

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • MrCommunistGen
    New Member
    • Jul 2018
    • 7
    • USA
    #1

    Polk Audio RTi100 Plate Amplifier won't power on and intermittently honks and buzzes

    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!
    Tags: None
    • budwich
      Badcaps Legend
      • Jul 2015
      • 3097
      • Canada
      #2
      Re: Polk Audio RTi100 Plate Amplifier won't power on and intermittently honks and buz

      The nice people at polkaudio.com sent me schematics for psw202 (old) recently so they have some things around. Of course, that doesn't mean parts might exists or can be found. I found that the caps on associated with the "front end" (ie. power) had issues along with possibly the IC AMP on a chip. I gave up as working with the board was difficult as there was solid thermal glue everywhere.

      I attached this herein... it might provide some clues IF it is close to your design.
      Attached Files
      Last edited by budwich; 07-12-2021, 05:49 PM.

        Comment

        • Per Hansson
          Super Moderator
          • Jul 2005
          • 5895
          • Sweden
          #3
          Re: Polk Audio RTi100 Plate Amplifier won't power on and intermittently honks and buz

          I would say the inner CapXon in this picture looks both bulged and sits at an odd angle.
          In any case with caps of such bad brands it would not be strange with silent failures also (dried up due to heat)
          Desoldering all caps and testing them on a cheap eBay "component tester" might be revealing.
          Or if you don't have one just ordering new caps and replacing them all as a start with reputable brands.
          Also it is well worth to check the PCB for bad solder joints with a good magnifying glass or loupe.

          Attached Files
          "The one who says it cannot be done should never interrupt the one who is doing it."

            Comment

            • MrCommunistGen
              New Member
              • Jul 2018
              • 7
              • USA
              #4
              Re: Polk Audio RTi100 Plate Amplifier won't power on and intermittently honks and buz

              First update:
              I looked into this a bit more and it turns out that it is NOT the transformer that's buzzing -- which is good news -- as that part would seem to not be replaceable.

              Second point:
              Originally posted by Per Hansson
              I would say the inner CapXon in this picture looks both bulged and sits at an odd angle.
              Good observation. I'd just assumed that it was installed a bit crooked. However, while trying to narrow down what component was buzzing I poked at the tilted capacitor and noticed that the lead on the raised side is completely detached from the capacitor. So yeah, that's dead.


              My thoughts:
              Ordinarily, I'd be comfortable just desoldering and replacing those caps myself, but after spending FAR TOO LONG trying to free the amplifier board from the rest of the plate so I can access the primary caps, I've given up. The caps are very solidly glued down on one end which, combined with the heatsink directly above them, makes accessing them very difficult. For a novice this is more than a bit intimidating.

              I don't know enough about tearing these things apart to non-destructively separate the power board from the rest of the plate with all the connectors, switches, and dials excessively glued together... so I think I'm just going to send these off for repair.

              As I mentioned before, these have strong sentimental value to me, and I'd rather not risk break something, so at this point I think I'm just going to send them off for repair.

              I appreciate the input from the community. I definitely want to actually repair some more stuff for fun as well as experience, but not these amplifiers under these conditions.

                Comment

                • Boats1997
                  New Member
                  • Aug 2021
                  • 2
                  • USA
                  #5
                  Re: Polk Audio RTi100 Plate Amplifier won't power on and intermittently honks and buz

                  I picked up a pair of Polk RTi100 yesterday with the same issue on one of the amps. I'm going to send the amplifier for repair. This shop does the repairs for about $97 shipped. https://www.ebay.com/itm/253344310964

                  While the amp is being repaired, I'm going to sand and paint the cabinets to match my Polk RTi70's.
                  Attached Files

                    Comment

                    • Boats1997
                      New Member
                      • Aug 2021
                      • 2
                      • USA
                      #6
                      Re: Polk Audio RTi100 Plate Amplifier won't power on and intermittently honks and buz

                      Here are few pictures from the RTi100 refresh project, one amp was mailed out today for repairs.
                      Attached Files

                        Comment

                        Previous template Next

                        Related Topics

                        Collapse
                        • jinu_j
                          How to test Subwoofer Amplifier with only a multimeter
                          by jinu_j
                          Hi Folks

                          Need some advice on how to test a subwoofer amplifier if i have access to only a multimeter.

                          Problem
                          I have a Boston Acoustics active Subwoofer (soundware S). Its rated output is 200W. But the output i am getting is very low i can barely hear/feel it even if put the gain at max. I replaced all the capacitors in the Subwoofer amplifier but still no change.

                          Is there anyway to test this without getting an oscilloscope/Function generator to see if the fault is with amplifier, driver or the source??

                          Any advice would be appreciated...
                          08-29-2024, 02:05 AM
                        • taligent
                          Polk PSW250 subwoofer amplifier constant hum repair
                          by taligent
                          Symptoms: Sub works, but produces a constant low level hum/buzz.

                          Troubleshooting: The amp uses CapXon capacitors, the first (and only) troubleshooting step was pulling the caps (other than the large power supply caps and non-polar caps) and testing with an AVR transistor tester (upgraded with a precision voltage reference and 0.1% reference resistors):
                          Code:
                          Part  Original Measured   ESR   Vloss
C4  100uF 25v  75.62uF  2.1 ohm  3.3%
C12  22uF 50v  22.54uF  8.5 ohm  4.7%
C14  220uF 25v  231.1uF  0.34 ohm  1.8%
C15  220uF 25v  227.2uF  0.45 ohm
                          ...
                          02-11-2021, 11:40 AM
                        • Eh546
                          Polk PSW125 capacitors choices for a beginner.
                          by Eh546
                          I was looking to repair my Polk PSW125 subwoofer plate amplifier, i've checked around the web and it seems to be a capacitors problem.

                          Took apart the amp, and made a visual inspection, everything's seems fine, fuse ect no burn marks, but i noticed 3 caps that were a little bit bulged. One 400v 150uf, one 50v 47uf, and two 63v 47uf.

                          I noted each caps voltages and uf anyways, and made a list on digikey. Some recommended Nichicon and Panasonics ones (FR and FM) serie. So I tried to stay with the Panasonics FM-A serie.

                          I would like to know if the caps i selected...
                          Blocked
                          https://www.digikey.ca
                          12-21-2023, 07:28 PM
                        • rustinjust
                          Please help, subwoofer connected to tv, read description below
                          by rustinjust
                          I've got a subwoofer that I've had for nearly 20 years, it did come with a basic remote which I've lost. It's a generic make of subwoofer, I can't see a brand sticker on it. It comes with 2 speakers.

                          Question recently I've connected it up to my tv which has greatly improved the sound on my tv, however I'd like to be able to mute the subwoofer when ads come on or just mute it when the phone rings etc. I tried using a cheap all in one tv remote on the subwoofer and the volume button would only work to increase volume but not turn it down or mute it

                          Is there a way of...
                          10-28-2023, 07:09 AM
                        • rustinjust
                          Please help, where can I get a remote for my subwoofer?
                          by rustinjust
                          I’ve got a subwoofer that I’ve had for nearly 20 years, it did come with a basic remote which I’ve lost. It’s a generic make of subwoofer, I can’t see a brand sticker on it. It comes with 2 speakers.

                          Question recently I’ve connected it up to my tv which has greatly improved the sound on my tv, however I’d like to be able to mute the subwoofer when ads come on or just mute it when the phone rings etc. I tried using a cheap all in one tv remote on the subwoofer and the volume button would only work to increase volume but not turn it down or mute it

                          Is there...
                          10-28-2023, 03:43 AM
                        • Loading...
                        • No more items.
                        Working...