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Thread: Soundcraftsmen DX4200 Schematic

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    Soundcraftsmen DX4200 Schematic

    I am looking for either a schematic (preferrable) or someplace to repair my DX4200. I have people that are willing to do it but without a schematic I am kind of sunk. My next alternative is to find someplace that would do the repair. Any help would be appreciated. Thanks!

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    Senior Member gferrell's Avatar
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    Whats wrong with it and what is it doing?
    XPL 200's, XPL 160's, XPL 140's, L7's, L5's, Homemade L Center, 4412's, L60T's, L3's, L20T's and still looking.

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    It blew a channel and the guys that I want to have work on it can't do it without a schematic. I can't seem to find any information and I would be willing to buy another one if I could.

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    Senior Member bigyank's Avatar
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    No affiliation but I have had success ordering from here:

    http://www.servicemanuals.net/Servic...42/detail.aspx
    Basement: JBL SVA-1800 and 2226H DIY Enclosures Computer room: Control-5:Control SB-2 Living room: JBL 240ti

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    Senior Member duaneage's Avatar
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    Quote Originally Posted by redsteel View Post
    It blew a channel and the guys that I want to have work on it can't do it without a schematic. I can't seem to find any information and I would be willing to buy another one if I could.
    If your repair shop can't troubleshoot a preamp using plug in op-amps that are identical throughout then I would find another shop. They aren't that complicated.
    Why buy used when you can build your own?

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    I had the same problem with a SP4002. There are a few differences and updates but layout is the same. Unlike amplifiers which have lethal voltages everywhere even after turn off (some), there's not high voltage anywhere in the circuitry of your preamp, yours should run on +/-15V, max +/-17V. The transformer and ac sockets are encapsulated in their own section so there isn't a big chance of touching them. If you plug a set of headphones to the tape 2 out socket on the front panel and then press equalize, then press route to tape record, choose your source, play some music and play with the eq sliders. If you hear both channels this way plus the eq effects and not through the normal headphone outputs then the rc4136 quad opamp right in the middle of the preamp board is bad (the bottom board under the eq board attached to the front panel). This ic can be removed with ease since it is on a socket. No desoldering is needed.

    Name:  rc4136.jpg
Views: 872
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    Post a pic when possible.

    RC4136s are $0.85 at http://www.futurlec.com/Linear/RC4136Npr.shtml

    If you can find a TL075 instead do your ears some good and replace it with it. The TL075 is lower noise, better performing and fits without an adapter. Or you might want to go the extra step and get a brown dog adapter from cimarron technology with a couple of better sounding opamps.

    http://cimarrontechnology.com/rc4136upgradeadapter.aspx

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    Senior Member bigyank's Avatar
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    Quote Originally Posted by rickedd46 View Post
    I had the same problem with a SP4002. There are a few differences and updates but layout is the same. Unlike amplifiers which have lethal voltages everywhere even after turn off (some), there's not high voltage anywhere in the circuitry of your preamp, yours should run on +/-15V, max +/-17V. The transformer and ac sockets are encapsulated in their own section so there isn't a big chance of touching them. If you plug a set of headphones to the tape 2 out socket on the front panel and then press equalize, then press route to tape record, choose your source, play some music and play with the eq sliders. If you hear both channels this way plus the eq effects and not through the normal headphone outputs then the rc4136 quad opamp right in the middle of the preamp board is bad (the bottom board under the eq board attached to the front panel). This ic can be removed with ease since it is on a socket. No desoldering is needed.

    Attachment 55164

    Post a pic when possible.

    RC4136s are $0.85 at http://www.futurlec.com/Linear/RC4136Npr.shtml

    If you can find a TL075 instead do your ears some good and replace it with it. The TL075 is lower noise, better performing and fits without an adapter. Or you might want to go the extra step and get a brown dog adapter from cimarron technology with a couple of better sounding opamps.

    http://cimarrontechnology.com/rc4136upgradeadapter.aspx
    Now that I am an owner of an SP4002 myself, I am thinking about springing for the adapter you list. TL075's are very pricey when found and I figure why not bring this preamp into the new milennia. \
    Basement: JBL SVA-1800 and 2226H DIY Enclosures Computer room: Control-5:Control SB-2 Living room: JBL 240ti

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    Quote Originally Posted by bigyank View Post
    Now that I am an owner of an SP4002 myself, I am thinking about springing for the adapter you list. TL075's are very pricey when found and I figure why not bring this preamp into the new milennia. \
    Yes, that is definitely the best route. I used the TL075 because they were in the phono section. I think the previous owner upgraded them. When choosing op amps for the browndog adapter remember some op amps need small compensation caps across the power supply pins for stability to avoid oscillation. These can be soldered on the bottom of the preamp board.

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    DX4000 (preamp minus eq) internals, (picture stolen from another forum, apologies to the poster if needed).

    Notice the main op amp in the middle under the bunch of wires (purple, gray, black, etc.)

    There's only 4 active components (4 op amps) not counting the PS regulators. So fixing this isn't as hard as it looks. If there aren't any visually burned resistors or blown caps then the op amps are the only thing to replace.
    Attached Images Attached Images  

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    SP4002 with eq board removed for access. Note that it has one less op amp because it does not have the inverting circuitry used on the DX4002 for bridging amplifiers.

    Name:  DSCF4172.jpg
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  11. #11
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    A full pic.

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