M-Audio Firewire 410 has bad input ...

[Comsat72]

Hi All --

Have an M-Audio Firewire 410 and the No. 2 multi input is wonky.

It no longer has phantom power and the levels are suddenly much lower than No. 1.

Anyone know what causes this?

Is it fixable/worth fixing, or no?

Thanks!

[drunton]

It sounds like one of the DC blocking caps between the input and the first stage op-amp is probably bad. It could be that just one opened up and there is simply no input getting to one side of the opamp.

It's worth fixing if you want to experiment. If the line input works fine you run the risk of killing it along the way - if you don't have the right tools. You can do the basic troubleshooting with a DMM.

With it plugged in, check the two XLR pins for 48V, I would assume one will not have it, maybe both. Then, with it unplugged, trace that signal path back from the input looking for the large-ish blocking caps. Use the DMM to see if one side is shorted. An open cap might need a o-scope to trace where the signal drops-off. Replace the faulty cap. Look for burned resistors along the way, sometimes it will be easily visible.

[Comsat72]

Thanks for the reply, I will check it out as soon as I get home!