Weird green liquid flux?

[asfi]

I'm in the process of bringing back from the dead a mid-1970s Twin Reverb that was "blackfaced" by.....a mechanic? a blacksmith? a plumber? Certainly not an electronics tech, if the quality of the soldering is any indication.

From the outside, the chassis looks fantastic, but that's because the metalwork's been cleaned up, and all the transformers have been refinished with black or silver paint. Under the hood is another story altogether.....

But yeah, the soldering. Some of it looks like this, with blue-green liquid on the joints. What the hell is this stuff? It looks like threadlocker though it doesn't smell like it. I'm redoing all the solder joints this clown had touched with their soldering gun but am wondering how aggressively I need to clean up the mystery liquid. I did strip down and wash the two smaller eyelet boards (rectifier/bias and filter cap) but don't really want to do this much with the main eyelet board unless I have to.

[Jazz P Bass]

Those caps look as if they are leaking.

The electrolyte may have corroded the solder joints.

[xtian]

Funky! Maybe the green is an oxide of copper?

[Justin Thomas]

Those caps are definitely leaking. As for the green color, I've seen it under the insulation of many a silverware and Ampeg of 70s vintage. I think it's a breakdown in the insulation of the wires myself, sort of like the lifeguards that off-gas and leave the slimy corrosive mess... I bet the insulation around the green stuff is more sticky and gummy than rubbery...

My usual fix is, well, anything that's poison-green in color is probably poison...

Justin

[Leo_Gnardo]

As for the green color, I've seen it under the insulation of many a silverware and Ampeg of 70s vintage. I think it's a breakdown in the insulation of the wires myself, sort of like the lifeguards that off-gas and leave the slimy corrosive mess... I bet the insulation around the green stuff is more sticky and gummy than rubbery...

My usual fix is, well, anything that's poison-green in color is probably poison...

Leprechaun juice! I've run across it too in the same kind of places. Mostly I ignore it and yes it's probably poison so don't eat it and wash hands well if ya get any on you. Would be a hoot to find out 'zackly what it is. I suspect a breakdown product of old vinyl insulation colored by copper salts. Yummy!

[Mick Bailey]

Evey now and then I get an old amp where acid flux has been used. Some cored solders use this, too. There also used to be 'universal' kinds that soldered aluminium, stainless, zinc, as well as regular materials. Fluxite, a gel zinc chloride product was very common here in the UK and the company actually advertised it for radio work. These fluxes are hygroscopic and maintain an acidic environment and corrode the joint. The difference in appearance is that the rosin-based fluxes leave the hard, shiny residue. Usually an acid flux will have formed a green crystalline deposit around the joint.

The plastics used in old vinyl insulation break down because they weren't 100% stable. In particular, the plasticisers and other compounds migrate or distill out and react with the conductors. I've had old reels of hookup wire where the conductors are eaten away, gone brittle or are so corroded as to be unsolderable.

+1 regarding the caps. They're long overdue for replacement and probably the rest of the electrolytics too.

[asfi]

Yeah, yeah, those caps are well and truly done for.

The mystery is that all the solder joints in the capacitor "doghouse" were ugly and amateurish, which given the rest of the work on this beast suggests that the "tech" replaced the originals with....equally old parts, possibly even salvaged from another amp. Probably not the most ridiculously stupid thing I've run across, but near the top of the list, surely.

[asfi]

Belatedly, I just discovered this appnote from Kester. I've no idea if this is the same thing or not.....

https://www.kester.com/Portals/0/Doc...ion_Global.pdf

[nevetslab]

Belatedly, I just discovered this appnote from Kester. I've no idea if this is the same thing or not.....

https://www.kester.com/Portals/0/Doc...ion_Global.pdf

For years, I periodically come across a similar green film between wire insulation and the stranded wire. I've found it on AC mains cable wires more often than others, but usually associated with wire core and it's insulation. Nice to see some app note to help explain it. Nice find!