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Recapping an Onkyo TX-3000

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  • Recapping an Onkyo TX-3000

    I local guy came to me to help him repair his old Onkyo TX-3000. It's more of a sentimental fix than one for financial benefit, so I took it on. You can buy one in working condition for ~$60 on ebay, so I told him I'd give it a shot, for parts plus $30 for my time. This is my first real re-cap job, but I've done the recapping in a few of the Lepais and I'm pretty handy with the desoldering and soldering irons.

    Well I was able to get all of the electrolytic caps replaced on the main power supply board (except the 12000uf caps, over budget but seem fine) and the amplification board. All of the rail voltages look great, and the left channel works when I bypass the relay, but the right channel has 8.5v DC running through it when I bypass the relay. This DC voltage isn't tied to the volume or any signal input, just a constant value. Any clue where I should look next to get it up and running?

    I have a multimeter and such. My circuit tracing skills need a little work though. I just don't know where to look next now that the poly caps are replaced. The ceramic caps should be fine shouldn't they?

    There are no hot-spots on the board or anything to hint towards any given area being an issue. I did a thorough deoxy cleaning on the unit as well.

    The manual can be found online HERE or if that direct link doesn't work, on HifiEngine it is this page (though you have to log in to DL): http://www.hifiengine.com/manual_lib.../tx-3000.shtml

  • #2
    Re: Recapping an Onkyo TX-3000

    No repair gurus around today I guess? :(

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    • #3
      Re: Recapping an Onkyo TX-3000

      Was it working properly before recapping?

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      • #4
        Re: Recapping an Onkyo TX-3000

        Originally posted by Ryan_M View Post
        Was it working properly before recapping?

        No, the relay wouldn't click before recapping either. I didn't measure the DC output before recapping because I couldn't get the relay cover off until I desoldered it form the board while recapping.

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        • #5
          Re: Recapping an Onkyo TX-3000

          Hmm, I cant seem to find a schematic. Is the amp section based on a chip amp or is it discrete components? Can you try a couple things and report back? Is the bias at the output positive 8.5V or negative? Put an input signal on the right channel and connect a speaker to that channel. Make sure you put a non-polar cap in series with the speaker to protect it from the DC other wise you will smoke the speaker! I want to see if anything is getting through and there is something F'd up with bias, or if the channel is completely dead. Also put the voltmeter across the coil for the relay and if you can, pull it and test it to see it is operating properly. Can you see a part # for the relay or is there a voltage rating for the coil (not the contacts) printed on it? I would start from the relay and not the amp channel itself as I bet when you find why the relay isn't operating you will find the source of both problems. Right now I'm operating blind on this, but given the fact that the relay is not working and given the level of bias at the output I'd be suspecting one rail secondary supply like a +/-12V regulator to drive the relay and some small signal components is borked as that would be a convenient voltage to drive both a 12V relay which is very common as well as power an opamp. Just speculation at this point though.

          Also can you post some good resolution pics of the amp section? I don't know how much good it will do but will give us a good idea of what kind of topology you're dealing with. Also what are the rail voltages?

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          • #6
            Re: Recapping an Onkyo TX-3000

            There is a schematic at the link I posted in the first post for you to look at. The relay works if I hold it open, and the speaker hooked to the right chqnnel is getting a signal in addition to the 8.5v offset. It sucks in and then continues to play from the offset position. I used a cheap buyout woofer to test that out. The relay is aupposed to be 12v I believe. I will get you more info on that and pictures if possible tomorrow . If you would like me to email you the schematic shoot me a pm and I'll send it your way. I believe it is before the relay but after the main power supply. The rail voltages into the amp board are good.

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            • #7
              Re: Recapping an Onkyo TX-3000

              Originally posted by Adam_G View Post
              The relay works if I hold it open
              I don't understand what you're saying by this.... so the relay works fine but it's not getting any voltage across it's coil? I see a link to download the user manual in the first post but dont see a schematic anywhere.

              Put that cap in front of the speakers and feed the signal and let me know if it sounds OK or if it is rough and grating. I did see in the manual that the amp section has a servo stage in the feedback loop. This is (typically) an opamp based circuit in the feedback loop specifically to eliminate DC offset in the output stage, so I think we're on the right track.

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              • #8
                Re: Recapping an Onkyo TX-3000

                Sorry double post.... forum is a little jumpy today!

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                • #9
                  Re: Recapping an Onkyo TX-3000

                  I'm sorry, what I meant was if I physically hold the relay open so it doesn't disconnect the amp from the outputs.
                  I will do the cap test to the outputs when I get home after work today. I don't think it's in the signal chain because with no input at all it's still putting out the same 8.5v or so.
                  I will re-open it up when I get off work as well and try to take pictures to help you out.

                  I'm sorry about the schematic, I linked to the wrong one. This site has the actual service manual and such. http://elektrotanya.com/onkyo_tx-3000.pdf/download.html (you need to wait a few seconds before you can download, but it's clean. It just says 'get manual' in normal text that is underlined)

                  Thank you for the help so far! Now you'll at least have something to work off of and won't be entirely blind!

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                  • #10
                    Re: Recapping an Onkyo TX-3000

                    OK sorry to dwell on this relay thing but it sounds like it's doing something different than what I thought initially... when you power up the unit the relay operates disconnecting the speakers from the outputs? And what you're describing is you need to hold it in place (so it can't operate) to allow the output signal to pass to the speakers? If this is the case then this is a DC protection circuit for the speakers and is doing it's job. I was under the impression this was a relay that will close after the amp has powered up and settled down, so I thought this was a problem since you manually had to move the relay to get the output signal to pass. If the former is the case then I'd definitely be zeroing in on that servo stage.

                    I'll go see if I cant get my hands on that schematic.

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                    • #11
                      Re: Recapping an Onkyo TX-3000

                      OK got the schematic.

                      Find Q602, it will look like this. The schematic says the part # is NJM4558DX which should be printed on the top of the IC. Dont pay too much attention to the letters in that part# as they usually only designate manufacturer and package information, the 4558 is the important part. Put the black lead of your multimeter on a good ground and with the other lead give me the DC voltages of all the pins, don't forget the +'ve or -'ve. In case you don't know the pin numbering scheme for DIPs you can open up the data sheet in the link I gave you above. While you are there have a good look at the components around this IC as well for burnt resistors or leaky caps.

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                      • #12
                        Re: Recapping an Onkyo TX-3000

                        Originally posted by Ryan_M View Post
                        OK got the schematic.

                        Find Q602, it will look like this. The schematic says the part # is NJM4558DX which should be printed on the top of the IC. Dont pay too much attention to the letters in that part# as they usually only designate manufacturer and package information, the 4558 is the important part. Put the black lead of your multimeter on a good ground and with the other lead give me the DC voltages of all the pins, don't forget the +'ve or -'ve. In case you don't know the pin numbering scheme for DIPs you can open up the data sheet in the link I gave you above. While you are there have a good look at the components around this IC as well for burnt resistors or leaky caps.
                        Alright sounds great, I'll tear into it first thing and get you those pin voltages. It will be around 6:00 EST

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                        • #13
                          Re: Recapping an Onkyo TX-3000

                          If you can still try the speaker thing too, I suspect it wont get very loud before it starts to sound ugly from clipping. Also the pics shouldn't be necessary now that I have the schematic.

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                          • #14
                            Re: Recapping an Onkyo TX-3000

                            For the pin measurements:

                            1: -8.28
                            2: -0.72
                            3: 0
                            4: -9.5
                            5: 0
                            6: 0
                            7: 8.26
                            8: 14.0

                            There are no visibly damaged resistors, and I replaced all of the electrolytic capacitors on that board, the film aren't visibly damaged at all.

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                            • #15
                              Re: Recapping an Onkyo TX-3000

                              ******* double posts...

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