Ellsept 6/12/2017 8:21 PM
Marshall AS100 Question
I have a Marshall AS100 amp. When I plug my guitar into the port marked instrument on the Acoustic Channel 2, it does not
Work. No sound comes through the amp. However, the Mic port works fine.. I have to plug my guitar into the Accoustic 1 Channel marked " input" in order to play and have a mic. Is there a problem with the Channel 2 instrument port or am I doing something wrong with the settings? I have watched some videos on demos of this amp, and they play the guitar through either port.. can you please advise? Should I take the amp in for service? Thank you. E. Milligan
g1 6/12/2017 8:52 PM
There is a switch labelled 'link channel 1' - make sure it is not engaged.
Ellsept 6/13/2017 6:39 AM
Thank you for your reply. I made sure the button wasn't pushed in, but it still has no sound coming out. Do you think the channel is bad? The mic part still works as it's supposed to.
Enzo 6/13/2017 8:17 AM
By definition, the channel is bad. You plug a signal into the input and nothing comes out. That is bad.

If the channel 2 mic input works but not the instrument jack, then I have to suspect the jack itself, or the link switch. The link switch may be in the proper position, but that doesn't mean it works right. Either one might have a cracked solder joint.
Ellsept 6/14/2017 2:28 PM
Thank you for the input!
Ellsept 6/18/2017 10:23 AM
Update on my amp... I sprayed canned air into the port and now some sound comes out but it is a lot lower than the other channel. If I turn the channel volume up loud enough to accommodate the guitar, the mic is way too loud.. suggestions??
Enzo 6/18/2017 12:08 PM
Blowing the dust out if good, but that doesn't mean the jack is OK or the solder to it.

If you look at the schematic you see the mic channel - which you say works OK - has a branch for the high Z input which is not. The signal path from that jack is through the jack, through the link switch, and into the IC100b which it shares with the mic strip. Your problem mostly has to be within that small area. There is also a resistor or two and a cap, but somewhere along that line is a fault.
Ellsept 6/18/2017 10:36 PM
Thank you so much.. I will have to take it in for service. Appreciate your info!