Super Fuzz Flux Residue

[FredB]

I have a Super Fuzz in for a trimpot installation. It was previously recapped, and who ever did that left flux residue all over the bacl of the PCB. I recently refurbish one of these, and found the original board in the unit I fixed up to have had quite a bit of flux residue left over from the factory.

My question is, is there any harm from washing off the flux residue. I was thinking that might expose the bare copper traces to the air and make them more susceptible to corrousion over time.

[Mark Hammer]

I routinely clean off excess flux with some methyl hydrate, and have encountered no ill effects. I clean it off to be able to get a clear glimpse of the solder joints and the traces when I make my own boards. The glare off the flux makes it difficult to spot cold joints, solder bridges, broken/cracked traces, and such, so removing it gives me a clean view. I don't know how much you are attemptiong to take off, but I just use a cotton-tipped swab, dip it in a bit of methyl hydrate and wipe.

The corrosion itself is essentially self limiting. In other words, the copper won't become more corroded. Once you have a layer of tarnish on the surface, the air won't come into contact with what's below. Personally, I like to tin my whole board so that I can easily solder on additional components on future, but since this is a vintage piece, the solder is where it eeds to be, and being able to add parts where they wren't originally is not part of the plan. So you're fine.

[cjlectronics]

Cleaning off flux residue also reduces the flux capacitance. Too much flux capacitance can send you back to the future.

[FredB]

I've been using acetone and a tooth brush. I have some denatured alcohol as well that I could try. It was the thought of exposing the copper to corrosion that just crossed my mind. I've read on amp building forums that all exposed copper wire should be tinned to prevent corrosion over long periods of time. So, I got to wondering.

The current pedal does seem to have a diminished fidelity, so I am expecting a noticable improvement in the upper mid-range and treble response after all the flux is removed.

For those who know about these pedals, the pedal I first had was one of the first units produced and had a significant bass response. The unit I have now is a later produced unit of the first model, without holes for the trim pot and brown poly caps and chip caps instead of the green "jelly bean" caps.

The bass response of this pedal seems a bit rolled off compared to the earlier produced pedal. When I have the board out, I will check for any value changes in the coupling caps. I was wondering if anyone else had noticed any variance in bass response of these pedals across the production years or models made.

[Mark Hammer]

1) Unless it is radically different, don't place too much faith in your recollection of the bass response. Humman auditory memory is notoriously fallible.

2) If it's an original, the electrolytics may well have dried out and fallen off spec. Lots of folks make it a point to change 35yr+ electros for newer ones.

3) The big bottom of the SF is a function of the scoop filter and the bass it leaves in. It's not that precise a filter, so it is easy to imagine variation from unit to unit.

[FredB]

I took some of the highs out and the bass came back plenty, see my new thread on this pedal.