Last time I saw this was non-momentary/non-latching footswitch problem,
sorting out the firmware failing by slowing down the switch action. That
fudge has worked fine. Now guitar input ok but a noise over the
microphone input that is white noise wavering in strength so it sounds
just like buffetting gusty wind noise. No change to the hash on jiggling
anything external. I've recorded the noise and are uncertain whether the
wavering is random or complex cycling in nature. I wonder if there will
be a cure this time, barely 2 years old.

Just before opening it up, I noticed the phantom button, in on position.
Repowering again 48V on and switching off, after 5 sec or so the
intrusion noise went. Testing for 48V , something tries to establish on
the mic line but drops to 0V over about 5 seconds. So the 48V subcircuit
needs exploring

"N_Cook" wrote in message ...

Just before opening it up, I noticed the phantom button, in on position.
Repowering again 48V on and switching off, after 5 sec or so the
intrusion noise went. Testing for 48V , something tries to establish on
the mic line but drops to 0V over about 5 seconds. So the 48V subcircuit
needs exploring



It is worth bearing in mind that not all units supplying phantom power do so
at 48v.

IIRC the Dynacord Powermate 1000 Mk1, for instance, uses something like 24v.



Cheers,


Gareth

Thought I'd start from the 48V switch trying to locate the generator.
But multiplexed into the uP like all the other switches. Only 63V caps
are at the mic input and L&R outputs. Other end of the board is a DC/DC
type inductive core lump next to 6 pin SMD IF8CG but no info found on
that topcode.
The owner was concerned as to whether he'd done something stupid,
despite it failing mid-song. Does owner psychology mean he did something
stupid, soon before the failure?

made 2012. That supply seems to be for 3.3V.
Looked for 2x 6.8K resistors at the XLR in and 2 are present, common of
those goes via control Q17 and Q18 and some small droppers to a 5 pin
SMD U23 and an even smaller inductor. U23 Marked
052
671
483
no info found of course playing with those numbers. p1 and p5
inductor/supply from 5V regulator, 2 gnd, 3 to diode, 4 output. Tomorrow
to probe the IC and Qs