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How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

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  • tyger23
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Originally posted by Rcstark View Post
    Excellent. What is happening is when I turn the volume from about 7/8ths to full volume the speaker come moves out seemingly all the way then settles back into position again. When I move it back to 7/8ths full I think what happenes is the opposite, it moves in then settled back into position. This is accompanied by a hum thay stays there when the pot is in these last positions. Second input is much worse then the first.
    OK - this helps a lot. This means that the offset is getting worse as the volume goes up, but the DC blocking caps (C104/C204) are doing their job and preventing a more serious issue. So long as the cone goes back to normal, the speakers should be OK. If it ever goes out and stays out, then that's bad.

    Basically - once we chase down the offset issue, this cone movement will go away.

    Originally posted by Rcstark View Post
    I succeeded in getting the right signal out of the molding...except the crimp on piece decided to stay inside of it. Can I just solder this to the bottom of the board afterwards?

    The voltage at c201 reads 0.5mV and at the right signal cable it fluctuates from .4-.8mV.
    That's a bummer. If you can get the crimp part out of the overmold, you can solder the wire to the top of the crimp. Otherwise, soldering to the bottom of the board is OK. The experiment seems to be revealing that the offset is coming from the rear panel board as I expected.

    Basically, what I would recommend at this point is to double check all of your work on the rear panel. If you can't find any solder issues, try removing all the parts you changed, clean them up, and replace them. However, I'm willing to bet that the issue is *either* the IC5 op-amp or the relay, with my money being placed on the IC5 op-amp needing replacement.

    Originally posted by Rcstark View Post
    Just to be sure, should these measurements be taken with a source plugged in?
    Also just double checked and it seems the positive leg of C104 is now about reading -16mV. If there is nothing connected to the rca jacks the measument changes back to a lower voltage.
    The measurements should have been checked in whatever manner you were getting the amp to "fail". So, it really doesn't matter. However - in good practice, you would at least use a grounding plug on the inputs (one that shorts the ring to the sleeve). This shouldn't be necessary, though - as there should be a pull-down resistor already there.

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  • Rcstark
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Just to be sure, should these measurements be taken with a source plugged in?
    Also just double checked and it seems the positive leg of C104 is now about reading -16mV. If there is nothing connected to the rca jacks the measument changes back to a lower voltage.

    Leave a comment:


  • Rcstark
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    I succeeded in getting the right signal out of the molding...except the crimp on piece decided to stay inside of it. Can I just solder this to the bottom of the board afterwards?

    The voltage at c201 reads 0.5mV and at the right signal cable it fluctuates from .4-.8mV.

    Leave a comment:


  • Rcstark
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Excellent. What is happening is when I turn the volume from about 7/8ths to full volume the speaker come moves out seemingly all the way then settles back into position again. When I move it back to 7/8ths full I think what happenes is the opposite, it moves in then settled back into position. This is accompanied by a hum thay stays there when the pot is in these last positions. Second input is much worse then the first.


    When I get home later today I'll check on what you just suggested and report back. I'm assuming I can just hack up an old rca cable and achieve the same effect instead of disassembling one? Or are you talking about the female connections to the back board?

    Thanks.

    Ok I read that wrong. I got you now. The cable from the wire harness

    Leave a comment:


  • ---k---
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Glad this thread popped up. I got one of these still sitting in the box never opened. I may have to try this out someday.

    Leave a comment:


  • tyger23
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Well, you most certainly have an offset on the right channel, but the fact that C204 and C207 are close to zero on the negative legs mean that the DC blocking caps are doing their jobs and the amp should not be putting out DC.

    When you said the cone would move all the way out, is it moving in one direction and staying there, or is it "vibrating" like a heavy bass track (i.e. moving in both directions)?

    Next, I would try and remove the right channel signal from the cable leading from the back panel. That's the wire in the pin #1 position. Usually, you can remove the wire from the connector mold by:
    1. Disconnect the cable from the main board.
    2. Find the little white "tabs" on one side of the cable connector.
    3. Gently insert an Xacto knife or other sharp object under the tab for the right channel signal.
    4. Very gently lift up on the tab, then pull on the cable for the right signal only.

    This should remove the right channel signal from the cable connector. Once this is done, re-insert the cable into the motherboard. This way, the left channel will work just fine and the right channel will be disconnected. Measure the DC voltage at C201 again, and then also at the exposed cable for the right channel.

    This should tell me where the offset is originating.

    Leave a comment:


  • Rcstark
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    C101 - .7 mV
    C201 - 106.4mV

    C104 - 2.5mV on the + leg
    C204 - 74mV on the + leg
    Negative legs show very close to zero

    C107 and 207 show very close to zero

    Leave a comment:


  • tyger23
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Originally posted by Rcstark View Post
    The speaker only moves on the right output. It would be great if you could point me at some things to check. And thanks again for helping, I know it's not really up to you to help out so it's really cool of you to do that!
    That makes things a bit easier to check. Sadly, I don't remember the schematics terribly well, so I'm having to look at my old pictures and notes and guess on a few things.

    First, a quick check. Make sure you're not in MONO, or Bridging mode.

    If you can measure between C101 and ground and C201 and ground and look for DC voltage when the amp is in the failing condition, that would be helpful. I'm betting C201 will show some DC offset (it shouldn't). However, C104 and C204 (should still have stopped the amplifier from seeing a DC input), so you need to check your rework near those as well. If I remember correctly, those are close to the far edges of the heatsink. Also look for DC voltage on either side of those capacitors (C104, C204). Look for DC voltage on either side of C107 and C207 as well.

    Leave a comment:


  • Rcstark
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Yeah it does move slightly on input one as we'll but not much I'm assuming that it would be fine to connect a decent speaker to that I care about it? Yes I have a multimeter, I attempted to measure the dc offset (I think that's what you were talking about before?) at the speaker terminals with nothing connected and get .6 mv on the channel in question, when the volume is at full it seems to fluctuate more than with it completely down.

    The speaker only moves on the right output. It would be great if you could point me at some things to check. And thanks again for helping, I know it's not really up to you to help out so it's really cool of you to do that!

    It might also be worth noting when the speaker moves it actually seems to settle back into position right away.

    Leave a comment:


  • tyger23
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    It sounds to me like there's an issue with the second input. It may be a bad op-amp or capacitor associated with Input 2. If input 1 is working well enough for you and the auto-switching is not bothering you, then I'd leave it on input 1 and be done with it.

    When on input 2, does the speaker cone move on both the left and the right channels, or just one of the two? Do you have a multimeter? If so, I can point you to some places to check.

    Leave a comment:


  • Rcstark
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Small update:

    I was able to fix the apparent ground hum, I cleaned up in between the traces on the main board and it looks like I may have let some solder flow to another when shorting between c101 and c102. I can still hear a very slight hum when turned up all the way but nothing like before.

    When I use input 1 and let it auto switch, if I pause the music and turn the volume knob to where it would move the speaker cone it only moves very slightly and hums slightly until the switch goes back to input two, then it moves the speaker cone again and I hear a hum again. So looks like one problem fixed or made slightly better? Does the fact it is happening worse on input two suggest anything?

    Leave a comment:


  • Rcstark
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Yes I did keep the auto switching circut. The op-amps have continuity everywhere they should and nothing is shorted together there, also the tabs are pointed toward the rca inputs. Checked and double checked with a meter. Man this is really frustrating haha!

    Leave a comment:


  • tyger23
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    That tends to indicate to me that whatever is wrong is on the rear panel board. I know there's several revisions of that amplifier out there, so I can't specifically state which one you have. However, in my design (the one pictured on page 1), the cable to the back panel provides power and ground to the preamp circuit and also provides the signals from the inputs into the main board.

    I would focus your efforts on the rear panel board. Did you do the rework to remove the autoswitch circuit? Double check that. Otherwise, start looking at the op-amps and make sure they're not reversed or have pins shorted together. When checking for shorts with IC's, look on the top and on the bottom. Sometimes solder will suck up through the hole and create a short on the top side of the board even though you were soldering on the bottom.

    Leave a comment:


  • Rcstark
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Ok so upon disconnecting the cable I lose the green power led and the speaker cone no longer moves when turning the knob

    Leave a comment:


  • Rcstark
    replied
    Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

    Ok. I'll check on that and get back to you. Thanks for the advice.

    And yes it was functioning properly before the modification.

    Leave a comment:

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