no input signal

[thehave]

My tascam 488 has no input signal with a sm57 mic. All I seem to get is hum, however, if I plug in my dean markley pro mag pickup I get a signal. I'm thinking the problem lies with an amplifier chip on the board with all the pots, but unfortunately the chip's identification is blank.

Any help would be greatly appreciated.

[edgarderbylive]

i have to wonder if it isnt the mic or the mic cable.....cause the line level still uses the channels pre amp, doesnt it???.......but youve probably already checked those

hmmmm....

[thehave]

I have checked the mic and cable. Both are just fine.
Thanks for the look and thought anyway.