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Infinity PS-12 Powered Subwoofer Fired Amplifier

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    #41
    Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

    I just wanted to thank everyone who has responded so far, I truly appreciate the advice.

    I'm going to recheck all solder joint again, Would it do any good to fold a thermal pad up and place it in where the thermistor melted through, Just as a buffer so that the heat sheild keeps the thermistor in place against the HS?

    Comment


      #42
      Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

      ^ Yes, any heat resistant material that helps it stay in contact with the heatsink is good. Just be sure to still use heatsink grease liberally applied on the thermistor. Another alternative might be that there are probably thermistors with their own metal mounting tabs integrated in, at better stocked electronics supply house like Digikey.
      Last edited by 999999999; 01-15-2014, 04:58 PM.

      Comment


        #43
        Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

        I have a PS12 sub with the same issues. C71 vented and C72 disintegrated in flames. I replaced C72 with an OEM cap. It now works, but it pops when it's turned up. It doesn't sound like a blown speaker, but more like it drops out or pops. I previously also had the standby issue and resolved that by disabling the standby mode so it's always on. Any ideas what else could be damaged that is causing this? Lots of threads on this subject, but this one seems to have to most knowledgeable responses so far!

        Thanks!

        Comment


          #44
          Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

          I wanted to chime in on this too. As of 2 weeks ago I've also had problems with my PS12. I opened up the amp and all the caps on mine don't seem to be exhibiting and leakage or bulging (I think I must be really lucky). The traces and all the solder points on the board look like they are in pretty good shape, no burn marks or anything like in some previous pictures (again, lucky).

          So, my problem is with the input detection circuit. When I turn on the power of the amp, the red standby light comes on, but when I connect it to the receiver the light won't switch to green, instead I get a flickering greenish-red light and no output. Before it got to this state I was having problems where the sub would drop out, and with the dropouts the light would go from green to red. Just as a test, I ran a 3.5mm headphone to RCA cable from my cell phone and when I turn the volume up to near-max on my cell phone I can get the light to turn green and the sub operates normally. So I believe it's something to do with the input detection circuit and it's right on the verge of detection.

          Now the pragmatist side of me is saying it's time for a new sub, but the engineering side of me won't leave it alone. So, I downloaded the PS-12 service manual and I once again opened up the amp. This time I looked at the board and found the output relay (K1, P/N:943-1C-48D) and figured if I just bypassed the relay then it would play with perhaps some potential side effects. Did that, but it didn't work, same issue as before, not working from the receiver but did work with the cellphone. As for the side effects, the only one I experienced was when turning off the amp I would get one small *thunk* in the powering off process. No real biggie, but definitely bypassed the soft turn-off.

          So, question for the group here, has anyone had success narrowing down the input detection circuitry and knows if there is a fix?

          Comment


            #45
            Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

            gonna have to replace all the caps.
            last 3 of these i did needed all of them replaced.high esr.

            Comment


              #46
              Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

              I've been a little busy and just got a chance to sit down with this board again.

              one leg of the thermister had a bunch of crap around it, so I brushed it off with a flux brush and the previous solder just wiped right off.;( go figure.

              I tried cleaning it up a bit and tried to resolder but as soon as i put heat to it some type of resin started flowing out not allowing me to solder.

              anyway around this? within seconds of applying the tip, she starts leaking.

              she'll clean up with some Alcohol but, starts all over again.

              any advice would be appreciated.
              TIA
              Attached Files

              Comment


                #47
                Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                MtPockets, the 3rd picture makes it look like the solder pad is completely gone, lifted off the board. If I am wrong and it is still there, you may have heavily oxidized copper that needs either very active flux (like plumber's acid flux) -OR- to use something abrasive to remove the oxidized copper exposing bright clean copper to solder to, something like metal polish or the gritty eraser on an old ink pen.

                Howver if it is the former, that the pad is completely missing, then the easiest thing to do at this point is get a scrap piece of thin solid strand wire, wrap one end around the thermister pin tightly with needle nose pliers, and run it above the trace it is replacing to the via to the right in the picture where you can either bend the end of the wire and put it in that via, or just hold it in place while you solder it there.

                Also you shouldn't need that much flux once you have something viable to solder onto like a piece of wire. When positioning the thermistor, try to hold it against the board while soldering so there is no slack, so it is held firmly in place. If this is not possible you can put a little bend in the lead on the opposite side of the PCB to give it something to stop further insertion.

                If this is not possible and the thermistor is flopping around loose you could thoroughly clean the PCB where the piece of wire is placed and permanently attach the wire, fix it in place with a little bit of epoxy or even lacquer paint, but leave the soldered portions untreated so they are still accessible later if you ever need to desolder this part for replacement. Epoxy or lacquer, whichever you have that seems more heats resistant since this component appears to be getting hot which is strange IMO, but does not change the fix at this point.
                Last edited by 999999999; 02-10-2014, 08:19 PM.

                Comment


                  #48
                  Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                  My PS-12 has the exact same damage. I think the C71 is what's burned out on the bottom as well. It's one of those tiny components, 0.1uf. Not sure why it's there, wired in parallel with the 6.8uf.

                  Comment


                    #49
                    Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                    Bypass caps:
                    http://www.seattlerobotics.org/encod...97/basics.html
                    Never stop learning
                    Basic LCD TV and Monitor troubleshooting guides.
                    http://www.badcaps.net/forum/showthr...956#post305956

                    Voltage Regulator (LDO) testing:
                    http://www.badcaps.net/forum/showthr...999#post300999

                    Inverter testing using old CFL:
                    http://www.badcaps.net/forum/showthr...er+testing+cfl

                    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                    http://s807.photobucket.com/user/budm/library/

                    TV Factory reset codes listing:
                    http://www.badcaps.net/forum/showthread.php?t=24809

                    Comment


                      #50
                      Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                      Hey guys,

                      Bringing this back from the dead, because I have an Infinity TSS-1200 that is fubar. I got it free from a local ad, and would like to save it from the landfill if possible. If you want me to start a separate thread, let me know.

                      The Scenario:

                      The LED turns green with a live audio signal, and back to red about 2 seconds after the music stops. The speaker makes no output at all, not even cracks/snaps.

                      The fuse is good.

                      None of the caps on the board show a voltage, nor any bulging or fluid leaking. C6 and C8 (3300uF) have the glue underneath and maybe some brown stuff that might be leakage or just old/burned glue. Hard to tell.

                      Resistors R6 and R7A are burning hot to the touch when the amp is on, even with nothing playing. R9A and R9 are warm. The area under these resistors has discolored brown from heat but is not burnt yet.

                      I don't see any other burn marks on the board, so it looks like this one died early without self immolating.

                      The 12" speaker measures about 3.9 ohm open load.

                      I understand from this thread that caps C72 and C73 (4.7uF and 6.8uF) often bulge and burn out.

                      I bought two Nichicon 3300uf caps and 2 Panasonic film caps for C72 & 73. I also bought four 5w 2.4K resistors to replace the ones described above (they look too small to be the called for design rating).

                      Questions:

                      - I asked a noted EBay repairer of these amps about this board. He said the scorch marks under the resistors, and the burning hot temperatures is totally normal. Not sure I buy that, but I've never worked on amps before. Is he right?

                      - None of the caps I'm replacing looked bad/bulging, so I expect that once I get everything installed, it probably will still not work. I'm replacing them on speculation because they so often burn out anyway, and to eliminate them from the list of variables. Any other test procedures I can perform to determine why the speaker is not seeing output?

                      I don't have a scope here, but maybe this is the excuse I've been looking for to invest in one. I do have several DVMs.

                      D

                      Comment


                        #51
                        Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                        djb, when you are talking about something you see, it is good to post pictures so we see it too.

                        There is no need to replace the resistors if they measure the correct value and that they are getting hot is a sign they are still conducting, although it would be good to reflow the solder joints if any are questionable.

                        Basically what you need to do is verify that the power supply is functional, producing what seems to be a correct DC voltage. Then there is the audio path, with a multimeter you should be able to measure a low AC voltage at the input pins of opamp(s) if any are present to confirm the signal makes it that far (of course you also need an audio source plugged in and playing music ), and at the output pins of the opamps if the opamps are working.

                        Likewise you should be able to measure voltage between the opamp power rails.

                        After the opamps (again, if present) check for signal present at either the input pins of the main power amp chip(s), or if it uses transistor pairs then signal on the base pin(s) of the transistors, and there may be a smaller then larger transistor(s) electrically in series for each channel, with the larger transistor(s) or amp chip on the largest heatsink(s).

                        In my opinion the most likely fault given what you have told us is a failure of the output transistor(s) or power amp chip... but more info and pictures from you may help. For all we know there could be a stuck relay or blown fuse. A scope usually isn't necessary to find a fault like this.

                        If you can dig up a schematic or entire service manual with schematic that may also help.

                        I don't see much point in bothering to replace the capacitors or resistors yet, if not bulging then they are not likely to be the problem. Yes it could be normal for the resistors to get hot, otherwise they wouldn't have used 5W resistors instead of lower wattage.
                        Last edited by 999999999; 04-16-2014, 04:32 PM.

                        Comment


                          #52
                          Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                          Did you download the service manual and do some voltage checking yet? and yes, good clear pictures are always needed.
                          Never stop learning
                          Basic LCD TV and Monitor troubleshooting guides.
                          http://www.badcaps.net/forum/showthr...956#post305956

                          Voltage Regulator (LDO) testing:
                          http://www.badcaps.net/forum/showthr...999#post300999

                          Inverter testing using old CFL:
                          http://www.badcaps.net/forum/showthr...er+testing+cfl

                          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                          http://s807.photobucket.com/user/budm/library/

                          TV Factory reset codes listing:
                          http://www.badcaps.net/forum/showthread.php?t=24809

                          Comment


                            #53
                            Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                            The board is identical to the others posted in this thread. I've gone over it looking for visible damage, nothing found yet (other than the brown area under the resistors). It has no burn marks or other visible flaws.

                            I do have the service manual. When I get it reassembled, I'll start tracing from the power supply out, to the limit of my ability, and report what I find.

                            That the resistors are conducting is of course true, but what I'm wondering is if they should normally be that _hot_. Hot enough to burn skin might cause the adhesion of the SMDs nearby to become questionable. Is that normal for this amp? Do people normally design amps that brown the circuit board with normal use? Like I said, I have no experience here.

                            Thanks for the help.

                            D

                            Comment


                              #54
                              Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                              If the resistors are not hot enough to melt their own solder joints and peel traces off the board, it won't be a problem for adjacent SMD unless they overheat themselves an additional amount to the point of damage.

                              Yes many products that put a significant amount of current through resistors end up with dark marks on the PCB, simply because they were too cheap to use larger resistors or heatsink them.

                              The resistors could be too hot from a downstream part that has a short, but there is no reason to focus on the resistors then so long as they have good solder joints and measure the correct resistance.

                              Now that I know it's the same PCB, I would go ahead and replace the two capacitors on opposite sides of the bobbin inductor because their ESR is an important parameter in the switching supply circuit.

                              However, you should still be able to proceed without replacing them. If the power supply circuit stays stable enough to run and produce a reasonable voltage then the amp should still produce audio output.

                              It looks like the components on the heatsink are transistors, is this correct? Get a part # off of them, look up the datasheet to get a pinout, OR you can trace the circuit to see which is connected to the power supply rail and which to the speaker output, then the remaining base pin can be measured for AC voltage to determine if the audio signal is making it that far (obviously while a connected source is playing audio), as well as the power supply pin receiving an appropriate voltage. I assume you know the circuit being live exposes high voltages and caution should be used when probing it.

                              If you have input power and input audio signal on the base pin but nothing on the 3rd pin, the transistor has failed. If you don't have input power then trace the power circuit. If you don't have input audio signal then trace the audio circuit backwards until you reach the point where there is signal prior to a component but not after it.
                              Last edited by 999999999; 04-16-2014, 07:36 PM.

                              Comment


                                #55
                                Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                                Hi everyone, my name is Derek and I'm experiencing the same issue as pockets was with my sub going in and out of standby mode. I'm attaching some pix for you to see the board itself. Upon inspection I don't see any burn marks on the bottom of the board. I don't see any broken runs on the board either. Note I haven't used the unit in months(shame on me) and it only ran for about 10 mins, enough time for me to hear/see the issue. It produced sound but kept switching back and forth between on and standby. I started my search online and found this informative thread. I'm hoping someone will chime in and help me repair this unit myself. I am somewhat of a DIY guy but I will admit I have very little knowledge of how electronics like this work so please bare with me.
                                Thanks in advance!





                                Comment


                                  #56
                                  Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                                  Bump

                                  Comment


                                    #57
                                    Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                                    OK, here is the service manual.
                                    So if you apply the sound to the input, then it will time out after 10 minutes even the input is still getting the sound at the input? per spec, the timer is activated if there is no signal for 15 minutes. Is the time out pretty constant at 10 minutes?
                                    BTW, did the LED also change color to RED when it goes into standby that will give us a clue if it is the detector/timer problem?
                                    Attached Files
                                    Last edited by budm; 10-02-2014, 10:57 PM.
                                    Never stop learning
                                    Basic LCD TV and Monitor troubleshooting guides.
                                    http://www.badcaps.net/forum/showthr...956#post305956

                                    Voltage Regulator (LDO) testing:
                                    http://www.badcaps.net/forum/showthr...999#post300999

                                    Inverter testing using old CFL:
                                    http://www.badcaps.net/forum/showthr...er+testing+cfl

                                    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                    http://s807.photobucket.com/user/budm/library/

                                    TV Factory reset codes listing:
                                    http://www.badcaps.net/forum/showthread.php?t=24809

                                    Comment


                                      #58
                                      Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                                      I'll have to reassemble it to check on the timer speculation, I was not aware there was a timer involved. Yes the LED was bouncing back and forth between red & green when it was making the clicking sounds, going in and out of standby(I assume)
                                      Thanks for the help, I had already downloaded the service manual from another thread, most of it is greek to me. Sorry for the delay in my reply. I'll keep a better watch on this thread now.

                                      Comment


                                        #59
                                        Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                                        From service manual:
                                        Auto On/Stand-By
                                        With the Power Switch ¶ in the ON position, the Status LED • on
                                        the back panel will remain lit in red or green to indicate the
                                        On/Standby mode of the subwoofer.
                                        RED = STANDBY (No signal detected, Amp Off)
                                        GREEN = ON (Signal detected, Amp On)
                                        The subwoofer will automatically enter the Standby mode after approximately
                                        10 minutes when no signal is detected from your system.The subwoofer
                                        will then power ON instantly when a signal is detected. During
                                        periods of normal use, the Power Switch ¶ can be left on.You may turn
                                        off the Power Switch ¶ for extended periods of nonoperation, e.g., when
                                        you are away on vacation.

                                        Check the DC Voltage on those two caps I marked.
                                        Attached Files
                                        Never stop learning
                                        Basic LCD TV and Monitor troubleshooting guides.
                                        http://www.badcaps.net/forum/showthr...956#post305956

                                        Voltage Regulator (LDO) testing:
                                        http://www.badcaps.net/forum/showthr...999#post300999

                                        Inverter testing using old CFL:
                                        http://www.badcaps.net/forum/showthr...er+testing+cfl

                                        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                        http://s807.photobucket.com/user/budm/library/

                                        TV Factory reset codes listing:
                                        http://www.badcaps.net/forum/showthread.php?t=24809

                                        Comment


                                          #60
                                          Re: Infinity PS-12 Powered Subwoofer Fired Amplifier

                                          Budm:

                                          "MUTE" is not 0V-active, it's -15V when active. The opamp runs from a dual-supply.

                                          You can confirm this by looking at how the bi-color LED is connected.




                                          Originally posted by service manual
                                          You may turn off the Power Switch for extended periods of nonoperation, e.g., when you are away on vacation.
                                          Just like an old tube TV!
                                          Last edited by kaboom; 10-14-2014, 10:07 PM.
                                          "pokemon go... to hell!"

                                          EOL it...
                                          Originally posted by shango066
                                          All style and no substance.
                                          Originally posted by smashstuff30
                                          guilty,guilty,guilty,guilty!
                                          guilty of being cheap-made!

                                          Comment

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