ART MPA Gold

fuzzsniffvoyage

fuzzsniffvoyage

Well-known member
2 channel preamp. The left channel mic input is not working, but the instrument input is. The VU meter moves and sound comes out for the DI, but no VU or sound on the mic. Checked cables and mic. So this tells me it's not a bad tube and the complete circuit is not bad, am I correct?

So I checked the xlr connections on the back, opened the box up and continuity tested each pin from the in to the ribbon cable that takes the signal to the main board.

I did not dig any further, I know very little about electronics. (Well enough to know don't mess with it.) I can solder a bit, and have been building my own fuzz boxes from other peoples designs off You Tube.

I sent ART an email asking for authorized repair centers. But could this be an easy fix?

Any ideas? Thanks.
 
Are you testing with a dynamic mic and, if not, have you checked for 48V on pins 2+3 with reference to 1?

If you don't know, you don't even need to open the unit to check.
Just turn on phantom power, set your DMM to DC voltage, put negative in hole 1 and positive in hole 2, then 3. Both should read 48VDC, or whatever the art specs at.

Does mic/di use a switching socket, like this? Switching sockets break a circuit when something is plugged in.
If that's the case you should see 3 terminals on either side of the socket, inside. Unplug any ts/trs and test for continuity sideways, if that makes sense.
3-3, 2-2, 1-1.
 
Steenamaroo said:
Are you testing with a dynamic mic and, if not, have you checked for 48V on pins 2+3 with reference to 1?

If you don't know, you don't even need to open the unit to check.
Just turn on phantom power, set your DMM to DC voltage, put negative in hole 1 and positive in hole 2, then 3. Both should read 48VDC, or whatever the art specs at.

Does mic/di use a switching socket, like this? Switching sockets break a circuit when something is plugged in.
If that's the case you should see 3 terminals on either side of the socket, inside. Unplug any ts/trs and test for continuity sideways, if that makes sense.
3-3, 2-2, 1-1.
Click to expand...

Checked with dynamic mic (SM57)

Ahh, a switching socket......let me look....Yes the socket looks exactly like that.

Thanks.
 
Found a schematic. Complicated little blighter isn't it?

If OP comes back I will have good look if he can make some systematic checks but I fear that circuit could be beyond him.

Dave.
 

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