Acoustic model 220 bass amp

[telejames23]

Anyone have a schematic? Trying to troubleshoot the boost switch on this, does nothing. Switch is good, don't know what it controls so need help beyond that. Anyone come across this problem? Thanks in advance

[g1]

Here they are

[telejames23]

That link brings up 114, 115

[Enzo]

I just opened it and see zip files for 114, 115 and 124, 125 and 220. All zipped

[vintagekiki]

https://music-electronics-forum.com/showthread.php?t=40939

http://www.ampix.org/albums/userpics/10075/Acoustic_220_service_manual.pdf

[telejames23]

Ah got it, thanks. What I'm seeing is that s103, the boost switch only appears in a block diagram somewhere on the power amp board. Can anyone tell me if I'm missing something here? Would like to find what this switch controls/activates as it doesn't boost or do anything.

[vintagekiki]

Yellow wire from S103 to power amp PCB 170079
Black/white wire from S103 to gnd of power input jack



1) correction

[g1]

Yellow wire from S103 to power amp PCB 170079
Black/white wire from S103 to gnd of power input jack

So it is the line called F/B in the original drawing, but resistor closest to switch is changed from 1K to 2K7 ?

[vintagekiki]

So it is the line called F/B in the original drawing, but resistor closest to switch is changed from 1K to 2K7 ?

Yes.
F/B (feedback) when Boost is on, resistor R15 (2k7) is connected in parallel with resistor R14 (2k7)