Soundcraftsmen DX4200 Schematic

[redsteel]

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!

[gferrell]

Whats wrong with it and what is it doing?

[redsteel]

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.

[bigyank]

No affiliation but I have had success ordering from here:

http://www.servicemanuals.net/ServiceManual/SOUNDCRAFTSMEN/DX4200%20SCHEMATIC%20DIAGRAMS/613342/detail.aspx

[duaneage]

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.

[rickedd46]

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.

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

[bigyank]

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.

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. \:D

[rickedd46]

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. \:D

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.

[rickedd46]

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.

[rickedd46]

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.

55168

[rickedd46]

A full pic.;)

55169