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Ensoniq SQ2 trouble shooting advice needed

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  • #31
    Yes, that big Tantalum cap tested shorted with my ohm meter and did not have the raising ohms to OL while in circuit. My BK ESR/DCR meter showed it had low DC resistance and the other ESR ohm range finder LED just flashed on and off continuously while in circuit? The ESR meter is rated for .47 micro farads and up. The Tantalum cap, if I'm reading it correctly shows 510 million pF. The PF value might be too small for the tolerance of the ESR meter to read correctly while in circuit. I'm still working on the Pico and micro farad math, so I'm not fully confident at computing it all yet. Once I pulled the Tantalum cap out of circuit, it tested fine on the ohm tests and the ESR /DCR tests. I'm glad I pursued this type of testing because I've learned quite a bit about capacitors and in circuit/out of circuit capacitor testing as well as parts vocabulary etc. Thanks guys for the insight, it helped quite a bit.
    Last edited by Jesse Pearson; 09-30-2018, 03:36 AM.

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    • #32
      Well, now test the resistance at the pads where that cap was. I think you may have found a short across one of the supply lines. The hard part is finding where exactly it is.
      Originally posted by Enzo
      I have a sign in my shop that says, "Never think up reasons not to check something."


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      • #33
        Right, I'm starting to see that I have a short that is dragging down the PSU and that's what I have to find right at this point. I'm studying on the subject quite a bit and tracing out the back of the main board as well as writing it out on paper in schematic style to help me understand where the voltage rails are on the board and what's connected to them. I have to figure out how to divide and conquer areas of this board so I can move on with my troubleshooting. Thanks g1...

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        • #34
          So disconnect other boards. Does the power supply itself hold up? Or does the short exist on an auxiliary board?

          ICs are always suspect, so are any getting hot?
          Education is what you're left with after you have forgotten what you have learned.

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