My SSL exploded! :(

This thing's been built and in service for weeks now. We've been using it all night for vocals, running two vocal mics through it (and living with the linked sidechain, since we're singing mostly harmony)... after about 6 hours of letting tape roll and just playing, I hear a *POP*!!!!!! and see smoke rise out of the SSL.

The four 100uF caps in the output stage all popped at once. Both sets of regulators are warmer than I'd like... I think I'm gonna move the 7x15's offboard and mount them to the aluminum case for future happy protection, but they weren't smoke-letting-out warm

the amazing thing is, it still works and sounds fine!

the caps are rated 25v, is that too low for that section? Seems like it should be alright, unless maybe extreme output voltage swing puts 30V on them?

are you sure they were in the right way around?

You somehow must have sent them phantom power. This is the only way in my imagination to acheive this effect.

The regulators ate too hot, if you can't touch them for more than a second. If you can touch them for longer than that without burning your fingers, they're probably alright.

Jakob E.

huh... I do have it hooked up to preamps with phantom on. Is there anyway to get around that?

..switch off phantom?

well, I'm using an ADA-8000... so it's all or nothing. Was using three inputs for mics, and running the two vocal mics through a separate pre, then through the compressor, then using the mic inputs of the ADA just because I didnt have the cabling on hand to use the balanced line in.

I assume the phantom is not present on the line in?

I assume the phantom is not present on the line in?

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Check your user documentation to make sure. If I remember correctly from the schematic, there should be no phantom at line inputs (and it wouldn't make sense anyway)

And never expose line outputs to phantom power - ONLY microphones are sure to survive this.

Many, MANY of modern-day electronically balanced outputs will burn out if exposed to phantom power.

Including anything built on the SSM2142 output driver - like all TC electronics gear.

Jakob E.

ok, well lesson learned

What's the actual reason those caps popped? just 48V on a 25V cap?

Considering the thing's still working, if i replace those caps, will this be good as new?

If I replace them with 50v or 63v caps, will it be somewhat more resistant to this problem in the future?

Regarding the warm regs, it occurred to me that there's something goofy with the metal tab of the case being connected to something other than ground on those? So screwing them directly to the aluminum chassis might be undesirable.

Sadly, I don't think there's quite enough room on the board to put heat sinks on them, considerinhg the close proximity to the big filter caps. Those caps get a tad warm too.

Also, I have no clue what to do to cool those 12v regs

What's the actual reason those caps popped? just 48V on a 25V cap?

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negative side goes outwards. they had 48V wrong polarisation.

Considering the thing's still working, if i replace those caps, will this be good as new?

Click to expand...

yes.

If I replace them with 50v or 63v caps, will it be somewhat more resistant to this problem in the future?

Click to expand...

no. better to avoid the problem by always keeping track of where you have your phantom - and using this for mics only.

I need to make some short XLR to TRS cables for this exact application. I just havent been able to bring myself to cut up mic cables

Would bipolar caps have helped?

Best regards,

Mikkel C. Simonsen

[quote author="tmbg"]I need to make some short XLR to TRS cables for this exact application. I just havent been able to bring myself to cut up mic cables [/quote]
don't cut
just make some new cables
make ALL your cables and then you know exactly what you have

this is the beginning of a healthy studio and control room

I agree completely... I just don't have a stock of XLR ends, and no place to get them locally (without spending something ridiculous like $8 apiece)

Easy solution... I have old cheapass mic cables which a) have intermittent cable and b) have cheap ends that wiggle around and make horrible noise when on a mic, but do ok on stationary gear. Cannibalizing those.

That's just Keef trying to generate some more work by putting in backwards caps!
:razz:

[quote author="tmbg"]huh... I do have it hooked up to preamps with phantom on. Is there anyway to get around that?[/quote]

Are you saying that you inserted the compressor *before* the mic preamp??

after a preamp... then before another preamp (with 0 gain, just used as a A/D converter to record).

Quote:

What's the actual reason those caps popped? just 48V on a 25V cap?

Click to expand...

negative side goes outwards. they had 48V wrong polarisation.

Click to expand...

Don't have the schematic here, but I figure they could also be connected reversed since there's no significant DC across those caps, correct ?
Rather not sending phantom to those outputs, but reversing might have reduced the problem ? (and had it perhaps left being unnoticed... - but sometimes it's better to know that there's something going on :wink: ).

Many, MANY of modern-day electronically balanced outputs will burn out if exposed to phantom power.

Click to expand...

The DI of my SWR bass-amp doesn't even use AC-coupling,
just a TL072 (driving potentially long lines...) and a 2k2 resistor in each leg.
It still works, but why didn't they make this a bit better ? :?

Regards,

Peter