FT-101E mod

[Hotel Zulu]

Hi all
Obviously this 101 has been through a few hands, somewhere along the way a project board has been added, I'm yet to work out exactly what it is but I think it may be a noise filter because when switched on it sounds like you're listening underwater.
It's wired to a toggle switch on the front panel.
I'm considering removing it because it's a very snug fit between the chassis and the case, so tight that the soldiered joints on the back had worked their way through the double sided tape causing some serious crackling on recieve when the rig was moved.
Does anybody recognise the mod ?

73's

 

[sunbulls]

I see a pair of UA741 OP amp chips. That leads me to believe it is probably a mic compressor or preamp. Tracing back all the connecting leads will tell the full story. For rigs back then that didn’t have that function, various compressor add-ons became popular. Usually connective wires to bypass that circuit are also provided as part of the mod. A way of making audio comparisons.