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Alternative to Faceplate/Preamp unit for Table Radios...

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  • #46
    I took some pics of the cable where it attaches just for fun...

    Front board attachment:

    Click image for larger version

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    It doesn't look to have a mechanical way to release the ribbon from the board, and I pulled on it as hard as I dared... so I think that one might be permanent.

    Rear board attachment:

    Click image for larger version

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    The little bottom black plastic piece pushes in and wedges the cable in once it's positioned. It has a real firm grip when locked in.
    Amazing they get the holding power they do with these tiny little fittings!

    Hope to mess with this on Sunday, church is cancelled due to the virus, so I'll have a little more time home.

    TomZ
    Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
    *Part 2 *Gluing multiple curved laminations of HDF

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    • #47
      You're dealing with 'headers', so searching for that might help you.
      PS- AllElectronics stocks some of this stuff, and is stateside....
      Later,
      Wolf
      "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
      "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
      "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
      "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

      *InDIYana event website*

      Photobucket pages:
      https://app.photobucket.com/u/wolf_teeth_speaker

      My blog/writeups/thoughts here at PE:
      http://techtalk.parts-express.com/blog.php?u=4102

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      • #48
        Originally posted by tomzarbo View Post
        It doesn't look to have a mechanical way to release the ribbon from the board, and I pulled on it as hard as I dared... so I think that one might be permanent.

        TomZ
        Actually, I think the cable slides out without a release. It's just very snug via the contacts. Wiggle side-to-side when pulling up. That is:alternating pulling more on "pin 1" than pin 20 and vice-versa.

        Could there be a pin hole to activate the release?

        https://www.youtube.com/watch?v=wewE6DbKhac


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        • #49
          No pin hole that I see. Also, wiggling side to side while pulling doesn't seem to do anything, I'm already pulling a lot harder than it seems I should. No need to go further, I have a connector and more ribbon cable coming anyway.

          TomZ
          Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
          *Part 2 *Gluing multiple curved laminations of HDF

          Comment


          • #50
            So I tried to short out the cap C34 and it seemed to work.

            Interesting... when I shorted the cap out, it did stop the output to the speakers, and amperage draw dropped from a bit over 500 milliamps to just under 300 milliamps.... but, doing so also muted the RCA line-level outputs, which I didn't expect. I had one channel of the onboard amp connected to a subwoofer speaker, and I also used the RCA output to connect to my Lepai and neo nano speakers.

            I thought the onboard amp would stop playing and go into standby while the RCA outputs would continue to have output, but that didn't happen; all output was muted.

            Just to be clear, I basically took an old set of multimeter probes with the banana ends connected, and shorted out the C34 cap...

            Click image for larger version

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            So now I'm confused. I'm assuming that I connected to the cap incorrectly, and basically did this wrong. Everything still works though so at least I didn't blow it up.

            If I did do this right, why did the RCA jacks stop putting out music?

            Sorry if this is obvious to everyone else, I seem to have a harder than normal time understanding this it seems.

            TomZ
            Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
            *Part 2 *Gluing multiple curved laminations of HDF

            Comment


            • #51
              Did you short out C34 before applying power, or after?

              If you applied the short before turning on power, it might make some sense. It looks like the RCA outputs would be coming from the TM2313 chip, which is controlled by the microprocessor (the F1C100s chip). Maybe the standby signal is routed back to the microprocessor, and it keeps the TM2313 chip muted until the power amp is out of standby mode. That's not a good way to design the circuit, IMO, but whatever....

              But if you applied the short after power was applied, what you are seeing is really weird, because it doesn't make any sense for the micro to monitor that signal.
              Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

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              • #52
                Neil, I had the power on and music playing first, then I put the test leads on the cap to short it out.

                Well, I'm thinking that this unit can be used in two configurations...

                (1) using the built-in amp(s) with a hefty 12v power supply (they have decent output on my pair of Bantams - a low sensitivity 3" woofer two-way using the ND91-4 woofer),
                or
                (2) just using the RCA outputs to your own amp; clipping the power leads to the built-in chip amp and hooking this up with an isolated DC-DC convertor...

                It looks like from the previous diagram that Mike posted in post #32 that just clipping the sixth lead in from both ends (Vcc) would just cut the power to the chip altogether and there would be no draw?



                Click image for larger version

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                TomZ
                Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                *Part 2 *Gluing multiple curved laminations of HDF

                Comment


                • #53
                  Originally posted by tomzarbo View Post
                  So I tried to short out the cap C34 and it seemed to work.

                  Interesting... when I shorted the cap out, it did stop the output to the speakers, and amperage draw dropped from a bit over 500 milliamps to just under 300 milliamps.... but, doing so also muted the RCA line-level outputs, which I didn't expect. I had one channel of the onboard amp connected to a subwoofer speaker, and I also used the RCA output to connect to my Lepai and neo nano speakers.

                  I thought the onboard amp would stop playing and go into standby while the RCA outputs would continue to have output, but that didn't happen; all output was muted.

                  Just to be clear, I basically took an old set of multimeter probes with the banana ends connected, and shorted out the C34 cap...

                  Click image for larger version  Name:	C34 Shorted.jpg Views:	0 Size:	6.5 KB ID:	1434234

                  So now I'm confused. I'm assuming that I connected to the cap incorrectly, and basically did this wrong. Everything still works though so at least I didn't blow it up.

                  If I did do this right, why did the RCA jacks stop putting out music?

                  Sorry if this is obvious to everyone else, I seem to have a harder than normal time understanding this it seems.

                  TomZ
                  Your probe test was correct.

                  That makes some sense. Muting the unit's line out until all the electronics have a chance to settle down lest an external amp produces start up pop/noise. The audio processor , TM2313, doesn't seem to have a specific mute or standby input pin. All it's mute functions are controlled by its data feed.

                  I'd try a couple of things. Test continuity between the C34's connection to Amp pin 4 and all the TM2313 pins. One probe on pin4 and thent run the other probe along the pins to see if you get a hit,. Try the same test along the ribbon cable connector on the odd chance the RC delay circuit is being sent back to the main board.

                  If putting the AMP in standby becomes a priority. You may have to cut the trace from C4 to pin 4 on the amp. Then ground pin 4. That would leave the RC delay circuit intact for the other functions using it.

                  Also, based on your earlier measurements, I expected the ma draw to be much lower when the amp's standby is forced low by shorting C34.

                  Comment


                  • #54
                    I tried connecting to Pin 4 (standby) on the chip amp and testing for continuity on all the pins on TM2413 and didn't get any hits. Same with all the ribbon connections. Then I did it again and still no hits. Occasionally, I'd touch the right side of C34 to check the lead hadn't come off and every time I had good continuity to I think the results are valid.

                    Once I'm sure how this is going to be used, I can determine if the on-board amp is enough, or does it need additional watts, and a little surgery on the amp. So basically, I'd cut the trace going to Pin #4 on the amp, so it's not making a connection, then find a ground and solder a piece of wire to the ground and pin #4 on the amp. Either that or if I can't find the trace, I'd have to exacto blade the base of the pin to cut it, then lift it off a bit and solder a ground line to that. That would leave the chip circuitry doing what it's supposed to, but still keep the amp in standby mode, reducing current draw.

                    Also, the other smaller faceplate/preamp unit I was messing with had about a 200 milliamp draw, there was no amp on that one. This does seem a bit high I guess comparatively.

                    TomZ
                    Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                    *Part 2 *Gluing multiple curved laminations of HDF

                    Comment


                    • #55
                      It's possible that the RCA outputs are connected to one of the amplifier outputs through a resistor and capacitor. The amplifier outputs are bridged, which means it is using two amps, one out of phase with the other. The speaker is connected between the two out-of-phase amps, which gives you effectively twice the voltage. But you can use a dropping resistor and DC blocking capacitor on either of those amps to create a line-level signal. If that is how the RCA outputs are connected, whenever the amp is put in standby or has the power cut, the RCA outputs will go dead.

                      However, it is also possible, and more likely, that the RCA outputs come directly from the TM2313 chip. The TM2313 pinout is shown below--it would be a connection from pins 22, 23, 24 or 25 to the RCA jack through a capacitor (need to block the DC voltage). The TM2313 doesn't have a dedicated mute pin--you must mute the device by sending serial data via the I2C bus (SDA and SCL) with a microprocessor. So if that is how the RCA outputs are connected, you could "fake out" the micro by having that standby signal go to the micro but isolate the standby signal from the amp (see next paragraph).

                      If you find out that the RCA outputs are connected to the TM2313 rather than the amplifier outputs (through capacitors and maybe some resistors, of course), then you can shut down the amp by isolating the standby pin from the board and grounding it at the chip. Just cut the trace going to pin 4 and add a small jumper from pin4 to ground (pin2).

                      If the RCA outputs are derived from the amp output rather than the TM2313, I would rewire them to use the output of the TM2313 instead (cuts and jumpers). Then you can disable the amp and still have audio

                      Click image for larger version

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                      Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

                      Comment


                      • #56
                        Also, You might want to consider dumping that board and using a different amp/TM2313 board. Search on Ali for TM2313 or PT2313 or TDA7313 and you will find boards that have the TPA3116 with a PT2313 chip. The microprocessor on your main board could be connected to the PT2313 using 3 wires: SDA, SCL and ground, and it wouldn't know that anything had changed, assuming the PT2313 and TM2313 are truly software compatible, which they are supposed to be(?) . You would need to make sure the audio is connected correctly, but once you did that, you would have a stereo 50W class D amp instead of a 15W class AB amp with its bulky heatsink.
                        Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

                        Comment


                        • #57
                          Originally posted by neildavis View Post
                          It's possible that the RCA outputs are connected to one of the amplifier outputs through a resistor and capacitor. [/ATTACH]
                          Yes, a possibility. There could be an easy test for that. Pick a line out RCA connector's ground and see if it is connected to PCB ground. If it is, it's likely connected to the TM2313 as that chip uses ground as one side of it's signal output.

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                          • #58
                            Originally posted by Millstonemike View Post

                            Yes, a possibility. There could be an easy test for that. Pick a line out RCA connector's ground and see if it is connected to PCB ground. If it is, it's likely connected to the TM2313 as that chip uses ground as one side of it's signal output.
                            The RCA ground does have continuity with the board ground mounting holes, as well as the antenna ground connection.

                            TomZ
                            Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                            *Part 2 *Gluing multiple curved laminations of HDF

                            Comment


                            • #59
                              Originally posted by tomzarbo View Post

                              The RCA ground does have continuity with the board ground mounting holes, as well as the antenna ground connection.

                              TomZ
                              That makes it 99% the line level is not coming from the amp. The amp's high level output cannot be tied to ground as it uses BTL mode to maximize power out given the nominal 12 V auto system. But if it was, the resistors used to lower the high level speaker output to a reasonable signal level would provide some isolation from ground. That would be a bad design. Though I have seen some questionable design decisions in the past ...

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                              • #60
                                Originally posted by Millstonemike View Post

                                That makes it 99% the line level is not coming from the amp. The amp's high level output cannot be tied to ground as it uses BTL mode to maximize power out given the nominal 12 V auto system. But if it was, the resistors used to lower the high level speaker output to a reasonable signal level would provide some isolation from ground. That would be a bad design. Though I have seen some questionable design decisions in the past ...
                                Think it would be worth trying to cut the #4 pin on the amp and connecting a jumper line to #2 (ground) and see if the line out is still functioning? I could undo if there was no RCA output.

                                I'm pretty sure I can pull that off. I can't get to the traces, but I think I would be able to put a thin X-acto blade and cut the leg off near the board and just lift it off a bit. Soldering a small line to #2 shouldn't be too hard, I have a pretty pointy soldering iron temp controlled. I could bend it down and re-attach if it didn't work.

                                Neil, I think if I can get the onboard amp to power down and still have the option to use the RCA jacks to run to an amp, that would be all I would personally need. That way it could be used two ways, amp-to speakers, or line-out to amp. I could use one of the isolated DC to DC converters of a higher amperage to run this thing while having the increased voltage to directly power a bigger amp. I'm afraid my success rate on changing boards would be pretty slim. I can tend to bite off more than I can chew with this stuff, although you guys have walked me through more than I could have figured out on my own.

                                TomZ
                                Zarbo Audio Projects Youtube Channel: https://www.youtube.com/channel/UCEZ...aFQSTl6NdOwgxQ * 320-641 Amp Review Youtube: https://youtu.be/ugjfcI5p6m0 *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                                *Part 2 *Gluing multiple curved laminations of HDF

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