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Thread: Mains AC choke necessary?

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    Mains AC choke necessary?

    Working on a Moog Taurus 3. Wouldn't power on. There's a small choke first thing after the power switch and fuse, one "side" of the choke was reading open. I bypassed the choke, and the unit powers up and works fine now. Thing is Moog has EOL'd this device and won't supply me any information. Choke just says 05120 on it. How neccessary is this thing? I know it's filtering out high freq noise, but there is also a nice MKT X2 cap across the mains, and some other smaller SMD caps as well. Safe leaving it bypassed, or should I try to replace it?

    Many Thanks!

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    Master Destroyer nosaj's Avatar
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    Choosing common mode chokehttps://www.coilcraft.com/cmc/index.cfm
    nosaj

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    Quote Originally Posted by nosaj View Post
    Choosing common mode chokehttps://www.coilcraft.com/cmc/index.cfm
    nosaj
    Thanks for the reply! It seems the 05120 corresponds to 0.5A 12uH. I can't find this specific combo anywhere, BUT I did find 0.8A 13.4uH. Same lead spacing and all, so I think I'll likely pull the trigger on this one. Close enough with a bit more power handling. Thoughts?

    https://www.mouser.com/ProductDetail...%2f8tlqQ%3d%3d

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    Master Destroyer nosaj's Avatar
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    Quote Originally Posted by Enoch0))) View Post
    Thanks for the reply! It seems the 05120 corresponds to 0.5A 12uH. I can't find this specific combo anywhere, BUT I did find 0.8A 13.4uH. Same lead spacing and all, so I think I'll likely pull the trigger on this one. Close enough with a bit more power handling. Thoughts?

    https://www.mouser.com/ProductDetail...%2f8tlqQ%3d%3d
    Personally I think it will be ok.

    nosaj

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    Thanks!

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    Lifetime Member Enzo's Avatar
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    You already know by bypassing it that it is not necessary to the operation of the unit. SO all it does is keep noise off the power lines. most anything remotely close should work fine...including your bypass.

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    Great, thanks for verifying Enzo!

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    Master Destroyer nosaj's Avatar
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    Quote Originally Posted by Enzo View Post
    You already know by bypassing it that it is not necessary to the operation of the unit. SO all it does is keep noise off the power lines. most anything remotely close should work fine...including your bypass.
    So it is for keeping power supply hash from backfeeding?

    nosaj

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    Quote Originally Posted by nosaj View Post
    So it is for keeping power supply hash from backfeeding?

    nosaj
    From what I've gathered so far, without a proper schem, is it's merely a common-mode ac choke to suppress high frequency noise on the mains. After this choke is an X2 cap, bridge rectifier, r/c filter stages, and the rest of a seemingly typical +/- ~83VDC supply. I know enough to know how much I don't know though, so could be mistaken somehow. The owner has a gig this Thu, so going to button it up as is with the choke bypassed, and have him use it that way. I tested it for a long while with no problems. Will throw in the replacement choke when it arrives. First piece of Moog I've been in. Seems like solid gear. Thanks for the help everyone!

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    Master Destroyer nosaj's Avatar
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    Quote Originally Posted by Enoch0))) View Post
    From what I've gathered so far, without a proper schem, is it's merely a common-mode ac choke to suppress high frequency noise on the mains. After this choke is an X2 cap, bridge rectifier, r/c filter stages, and the rest of a seemingly typical +/- ~83VDC supply. I know enough to know how much I don't know though, so could be mistaken somehow. The owner has a gig this Thu, so going to button it up as is with the choke bypassed, and have him use it that way. I tested it for a long while with no problems. Will throw in the replacement choke when it arrives. First piece of Moog I've been in. Seems like solid gear. Thanks for the help everyone!

    Just to avoid embarrassment if it is to prevent hash from backfeeding into mains. I'd find out if there's any wireless gear used and simulate in your shop to see if any SMPS hash is making noise or if a regular single coil guitar picks up trash..
    nosaj

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    Quote Originally Posted by Enoch0))) View Post
    From what I've gathered so far, without a proper schem, is it's merely a common-mode ac choke to suppress high frequency noise on the mains. After this choke is an X2 cap, bridge rectifier, r/c filter stages, and the rest of a seemingly typical +/- ~83VDC supply. I know enough to know how much I don't know though, so could be mistaken somehow. The owner has a gig this Thu, so going to button it up as is with the choke bypassed, and have him use it that way. I tested it for a long while with no problems. Will throw in the replacement choke when it arrives. First piece of Moog I've been in. Seems like solid gear. Thanks for the help everyone!
    It appears that Moog built their own version of a power line EMI filter rather than using a commercially available module such as one like that shown at https://www.mouser.com/pdfdocs/EJTSe...nletFilter.pdf .

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