MIDAS DL32 Channel Noise [SGM4510 Question]

[Philip_BlueFX]

Greetings!

I am repairing a MIDAS DL32 Stagebox that has noise present on a couple of channels. It seems on some of them the filtering capacitors where blown.

I have a question for the brainiacs though. I've no idea what the schematic of the DL32 looks like or the MIDAS preamps, however I can see that there's a 4580R Op-Amp for the amplification stage for each channel, there's also 2 x SGM4510 present for each channel. It's a "quad single-pole/single-throw (SPST) analog switch" and I would assume it's a power supply or phantom power kinda thing, but could it be something else? Each channel has 2 of these. Does it have anything to do with the AD conversion of the signal maybe? Any inputs would be greatly appreciated. Trying to gain any knowledge on the matter.
Thanks!

P.S. I notice on two channels with really blown caps, the SGM4510 also seems to be blown (it looks like it caught fire).

 

[Khron]

there's also 2 x SGM4510 present for each channel. It's a "quad single-pole/single-throw (SPST) analog switch" and I would assume it's a power supply or phantom power kinda thing, but could it be something else? Each channel has 2 of these.

I'm pretty sure that rather has to do with the digitally-controlled gain adjustment of the mic preamps.

https://en.wikipedia.org/wiki/Instrumentation_amplifier

As you can see, the gain is controlled by the value of a single resistor; they use those switches to adjust the gain with 8-bit resolution (4 "bits" per each quad switch, so 256 steps all in all).

 

[Philip_BlueFX]

I'm pretty sure that rather has to do with the digitally-controlled gain adjustment of the mic preamps.

https://en.wikipedia.org/wiki/Instrumentation_amplifier

As you can see, the gain is controlled by the value of a single resistor; they use those switches to adjust the gain with 8-bit resolution (4 "bits" per each quad switch, so 256 steps all in all).

Ah, makes all the sense yeah! I was speculating it's for the pad, phantom, mute functions and such, as they are controlled over the mixer but I assumed they happen in the box preamp section.

It's an extremely rare component though, I can't really get it anywhere else than AliExpress, which I'm quite afraid of for this purpose.
Any ideas as of where I could get a few of these (I think I need 3-5 for the blown up channels) or possible replacements?

 

[ccaudle]

or possible replacements?

Quad analog switches aren't that rare. Analog Devices have some (these parts are from the Maxim acquisition):
https://www.analog.com/media/en/technical-documentation/data-sheets/MAX4664-MAX4666.pdf

Just search for CMOS quad analog switch, and start comparing parameters and pin outs until you find one that is pretty close.
The SGM can run at up to 40V supply (or +/-20V), but may not actually have a power supply that high. Check what power supply the box uses, if it is just using +/-15V or +/-12V for example, you can get away with a replacement which has e.g. 36V max supply even though that isn't an exact parameter match.
The SGM device uses 1.8V control logic, that will be important. On resistance of 15.5 Ohms "typical," so around that or lower should be OK. Check the value of the resistors that are being switched to see how much difference in total resistance you will have if you use a part with lower on resistance. If the device resistance is being used as a significant part of the total resistance then it would affect gain matching, but hopefully the resistors are significantly higher value than 15 Ohms so if you use e.g. 5 Ohm devices it won't make that large of a difference.

Those Maxim devices were just an example, by the way, the logic control pins of those use TTL levels, not 1.8V logic, so not suitable as direct replacements. You should be able to spend some time on the search engines of component distributors and find something suitable.