This fx loop is designed to be patched in external effects as other Boss pedal and so on. I've re-bathed the board in contact cleaner to ensure all contacts are squeaky clean, all jack inputs & outputs are sprung properly, all solder joints have been redone just to be sure so it seems like there's a problem with the board itself - specifically with the grounding however the metallic/digital hiss & dips in sound still exist - albeit a slight bit less than before. Ive just bought a Boss NS-2 pedal with in and out lines and a send-return loop for effects. Temporarily I've connected a "manual" ground from the input to the output jack (not the FX send/receive loop) which seemed to cure it before I put it back in the housing. In doing so I think I may have stumbled across the issue - a bad earth. I've taken it to bits and I figured I'd probably replace it anyway as the repair cost is almost the same as a replacement. It's the perfect pedal to quiet down any pedalboard or effects setup. With that in mind, what other steps or tricks can I try to salvage my beloved NS-2 (or any pedal for that matter)? The NS-2 Noise Suppressor eliminates unwanted noise and hum without altering an instrument's natural tone. I have tried stripping it down and attacking it with contact cleaner as one of the jack inputs definitely crackles but not the pots (they're as clean as a whistle). It's out of warranty and Boss/Roland never got back to me with engineers in my local area (one tech support guy from Roland recommended I just replace the thing as it'd be less hassle but I'm loathed to do so as it was £75+ postage and I've had pedals last WAY longer with more abuse). It's powered by a 9V adapter (of which I've tried several of different brands), not battery powered. In complete isolation the sound issues happen the same as if it was in my board - so it's not the other pedals that's interfering with it here. There's no power issues (in terms of it not getting enough power or it trying to power other pedals). I took everything to pieces and isolated every pedal and found it to be the Boss NS-2.
When I have this routing it seems to completely kill any gain or effects on the. from there i have the effects loop send going into the send/return secondary inputs on the NS-2. So to explain I have the guitar going into the first input, then out into the amp. I recently took my board apart to redo all the effects and noticed that the output of the board was inconsistently dropping and returning and there was an occasional crackle when cables were strained. I am using a boss NS-2 with the effects loop function going into a Boss Katana 100w mk2.
I've got a Boss NS-2 that I've used for ~6 years without issue.