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FDP Forum / Performer's Corner / no phantom power light or power on Mackie Mixer

wborys
OldFartBassPlayerWalt

Robbinsville, NJ

what do you mean the bass is too loud?
Jan 31st, 2019 08:22 PM   Edit   Profile  

my friend called to help scope out a problem she had, so I tried to talk her through. The system she set up for a church play (mackie mixer, Crown power amp, two speakers) worked fine when tested with dynamic mics. Just like every year. But now it gives up nothing with the overhead condensors plugged in.

Phantom power light wouldn't come on, and apparently neither does the phantom power. Even with all the XLR inputs taken out. She's getting another mixer, but I just trying to figure out WHY this one is crippled. Apparently the fuse is OK, since its still working except for phantom.

Its a church basement system that everyone has their hands on. My thoughts are someone pushed a 1/4" plug into the TRS jack when the phantom was on, and the power supply fried.

DOES THIS MAKE SENSE?

OR I am worried that one of the XLR cables has a short, causing the meltdown. Could this be possible, even if the non-power mics are still working?

ANY thoughts shared would be appreciated.

Peegoo
Contributing Member
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Just beyond Mars

there's a world of fools
Jan 31st, 2019 11:43 PM   Edit   Profile  

It's probably a cap or resistor gone bad in the switch-mode power supply that sends 48vDC to the XLR ins on the channel strips. The switches for the p-power rarely fail.

A repair like this can cost upwards of $200.

How many p-powered condensers are they using? I ask because if it's just two, a really simple and cost effective work around is to buy a small dual-channel outboard p-power module.

You run two short XLR cables from the mixer's channel strip ins to the module outs, and then plug the mics' XLRs into the module ins.

Here's one. Note that the pic is a 1X, not a 2X

(This message was last edited by Peegoo at 02:56 AM, Feb 1st, 2019)

Roly
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Whitehorse Canada

I don't get out much
Feb 1st, 2019 01:20 AM   Edit   Profile  

Hi
Get a meter and set it to volts DC.
Engage the +48 switch on the mixer and measure from pin 1 to pin 2, and pin 1 to pin 3 on all mic inputs....both should read at or close to +48 DC. (- meter probe to pin 1 and + meter probe to the other pins)
Some entry level mixers don't supply true +48....Yamaha mixers are notorious for spitting out about +18.....that means that the mic or DI will work but will have limited headroom.
If you get a low reading, or no volts DC at all...it could be as simple as a dirty +48 switch or as serious as the +48 rail has failed.

Quick and dirty....pull the switch cap off the +48 switch and give it a shot of Deoxit 5......then exercise the switch.....on off on off several times.
If the issue isn't resolved something in the +48 rail has failed.
Beyond basic troubleshooting, I don't have the depth to offer further advice.
Mr Goo's advice is a good workaround...one I have used in the past.
cheers

Roly
Contributing Member
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Whitehorse Canada

I don't get out much
Feb 1st, 2019 01:59 AM   Edit   Profile  

Forgot to mention.....squish the end of the spray tube with needle nose pliers so it's flat, that will permit you to get more juice where it's needed and waste less.
cheers

wborys
OldFartBassPlayerWalt

Robbinsville, NJ

what do you mean the bass is too loud?
Feb 1st, 2019 08:00 AM   Edit   Profile  

Wow thanks guys!

On my way to the Church basement right now!

wborys
OldFartBassPlayerWalt

Robbinsville, NJ

what do you mean the bass is too loud?
Feb 1st, 2019 08:19 PM   Edit   Profile  

Update if helpful-

When we turned on the mixer this morning (with no inputs plugged in) it powered up perfectly, with the phantom power light lit up. I wonder if the short circuit theory resulted in a thermal shutdown, which cooled down over night.

Emboldened by this 'recovery', we plugged in two of the condensors, again with no problem.

The cable for the third mic had a gash in it, and pretty much looked like hot wires were contacting the ground shielding. The cable was hard wired to the mic, so I brought out the razor blade and soldering iron, and half an hour later- we were up 100%.





Peegoo
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Just beyond Mars

there's a world of fools
Feb 1st, 2019 09:58 PM   Edit   Profile  

That is fantastic, Walt!

So one of the mic cables was damaged and shorted, killing the power on the 48v rail.

Your speculation about thermal shutdown is probably the case. Most modern pro audio gear has built-in safeties because it's common even for people familiar with the gear to make a wrong connection that would instantly fry the older stuff.

Bravo!

FDP Forum / Performer's Corner / no phantom power light or power on Mackie Mixer




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