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SX-M2 phantom problems

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weroflu:
I was having some low level output problems with a SX-M2, sent it in for repair, clean bill of health reported, and then still experienced the same problems.

Tracked it down to insufficent phantom voltage. Phantom is about 3V below whichever supply voltage is fed, which made me think regulation is working but not the dc-dc converter.

However phantom was working fine during the checkup at repair, so it's a mystery.

The only thing I can think of now is that they used a higher voltage to test it at the shop and this is somehow responsible for it working there and not here. The only external power I have here is 12V. I have tried two sets of batteries as well.

Anyone have a clue to what the problem is?

Sonosax says that this is an older dc-dc converter and not replaceable, they are still working on finding a solution.

It may turn into my dedicated dynamic microphone amplifier.

stevetoney:
I'm not sure I understand what you mean "phantom is 3v below whichever the supply voltage is fed".  I haven't run a Sonosax extensively, but with an input voltage range from 12vto 24v, doesn't it supply 48V phantom regardless of the input voltage?  Regardless, I didn't use mine with batteries, but whenever I used it I supplied it with more than 12V external from a Tekkeon.  Could it be that since your external is at the low end of the range, that's your issue (though you said you'd tried batteries, which of course should give you at least 18V).  Stating the obvious other question...the batteries were good and the battery contacts are clean?

weroflu:
'm not sure I understand what you mean "phantom is 3v below whichever the supply voltage is fed".

It means if I feed it 12v external phantom measures at about 9.xV, if i feed 18v from new batteries phantom measures at 15.xV, and slightly used batteries result in phantom voltage of about 13.xV.


 I haven't run a Sonosax extensively, but with an input voltage range from 12vto 24v, doesn't it supply 48V phantom regardless of the input voltage? 

That's what's SUPPOSED to be happening but it isn't

Regardless, I didn't use mine with batteries, but whenever I used it I supplied it with more than 12V external from a Tekkeon.  Could it be that since your external is at the low end of the range, that's your issue (though you said you'd tried batteries, which of course should give you at least 18V). 

see above

Stating the obvious other question...the batteries were good and the battery contacts are clean?

Yes everything is good, i tried swapping cables a bunch of times too. Running a 1k tone through it worked fine with all the power sources, the problem looks like it's only related to phantom, but I have no idea why it would only appear here and not at the factory. I'm testing phantom right at the inout jack, no load, no microphones, no cables.

Compounding the problem is that it got a clean bill of health from the factory.

From my little knowledge of things electronic I remember that regulators drop voltage about 3v so that was my guess, but it doesn't solve anything.

hi and lo:
The Sonosax should measure ~47.5v at the input jack with no load (or at least, both of mine measure exactly the same). Certainly if you're measuring ~9-15v, something is definitely not right. I have no idea what might actually be wrong with the unit.

One thing to mention is that if you're using an external power supply, it must be at least 14v. The normal operating range is 14-24v. Between 12v and 14v, the unit will operate with the low battery warning light and significantly reduced headroom.

JD:
Not sure if it would help you out or not, but somewhere I have some basic electrical schematics for the SX-M2. LMK if you have any interest in them, I'll see if I can find them and post a copy.

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