Getting rid of that bad capacitor smell
June 11, 2018 9:12 PM Subscribe
I'm fixing an old stereo. Despite my best efforts to clean up leaked capacitor fluid with alcohol, it smells awful. I've scrubbed and scrubbed and it just seems to smell worse and worse. It's stinking up my apartment. How can I make the smell go away?
I'm fixing the same stereo mentioned in this question. It's a stereo from 1973, and I know electrolytic capacitors from pre-1979 can have pretty nasty stuff in them.
I've replaced pretty much every electrolytic capacitor in the unit. A lot of the small ones had leaked electrolytes onto their respective PCBs. I've cleaned up as much as I possibly could with a toothbrush, q-tips, and 91% alcohol. The smell seems to be getting worse, not better. The power supply seems to smell especially bad, despite having been thoroughly scrubbed after replacing all capacitors.
My hope is that the only reason it smells so bad is because the alcohol sort of rehydrated dried chemicals, and that it'll go away in a few days. But whereas before the smell was only noticeable when I had the case open and was working on it, it is now so strong that people you notice as soon as you walk in the front door. What the hell?
Are there any other treatments I should try? Do I need to just keep scrubbing in every little spot? Should I be concerned about the extra smell, or about dangerous fumes in my living space? The apartment is well-ventilated, and I always work with a bunch of fans everywhere, but it's also a small apartment and I'm basically working in my kitchen/living room.
I'm fixing the same stereo mentioned in this question. It's a stereo from 1973, and I know electrolytic capacitors from pre-1979 can have pretty nasty stuff in them.
I've replaced pretty much every electrolytic capacitor in the unit. A lot of the small ones had leaked electrolytes onto their respective PCBs. I've cleaned up as much as I possibly could with a toothbrush, q-tips, and 91% alcohol. The smell seems to be getting worse, not better. The power supply seems to smell especially bad, despite having been thoroughly scrubbed after replacing all capacitors.
My hope is that the only reason it smells so bad is because the alcohol sort of rehydrated dried chemicals, and that it'll go away in a few days. But whereas before the smell was only noticeable when I had the case open and was working on it, it is now so strong that people you notice as soon as you walk in the front door. What the hell?
Are there any other treatments I should try? Do I need to just keep scrubbing in every little spot? Should I be concerned about the extra smell, or about dangerous fumes in my living space? The apartment is well-ventilated, and I always work with a bunch of fans everywhere, but it's also a small apartment and I'm basically working in my kitchen/living room.
Given that the bias settings are questionable, are you sure what you're smelling is baked capacitor goo and not disintegrating epoxy transistor casings?
posted by flabdablet at 5:08 AM on June 12, 2018 [1 favorite]
posted by flabdablet at 5:08 AM on June 12, 2018 [1 favorite]
With pre-1980s capacitors you're looking at possible PCB exposure. There is not a great DIY solution to this as far as I'm aware - if you are solely interested in your own health you could let it off-gas/dry outside, but keeping PCBs out of the environment is the main reason they were banned. (Granted you'd only be contributing a tiny amount to the environmental load; it still fails the "what if everybody did it" morality test).
Also re: the smell, much pre-1990s equipment likely spent its entire operational life absolutely soaking in cigarette smoke, so at a minimum it's going to smell like my grandma's couch whenever it's warm. One of your major enemies here is that a lot of the materials you're looking at are absolute sponges for odors. Your best solution might ultimately be to keep it super well ventilated so you don't notice the smell building up.
posted by range at 5:39 AM on June 12, 2018 [1 favorite]
Also re: the smell, much pre-1990s equipment likely spent its entire operational life absolutely soaking in cigarette smoke, so at a minimum it's going to smell like my grandma's couch whenever it's warm. One of your major enemies here is that a lot of the materials you're looking at are absolute sponges for odors. Your best solution might ultimately be to keep it super well ventilated so you don't notice the smell building up.
posted by range at 5:39 AM on June 12, 2018 [1 favorite]
Could you spray the whole thing with that spray they use?
posted by at at 9:25 AM on June 12, 2018 [1 favorite]
posted by at at 9:25 AM on June 12, 2018 [1 favorite]
The power supply seems to smell especially bad
Audio equipment of that vintage will generally have an unregulated supply consisting of a large mains transformer followed by a bridge rectifier (probably constructed from individual diodes) and smoothing capacitors. Of these, the transformer is the only component that would normally run warm unless the amplifier is drawing enough current to heat up the rectifier, which it would normally only do when turned up loud.
Transformer windings are usually covered in shellac, and if that's starting to break down it can emit quite a sharp and pungent scent. If you're smelling something like a cheap blender trying to chew through ice at low speed, that will probably be what it is.
There might be a smallish linear regulator that provides stable supply rails for the preamp section, but I would not expect it to be drawing enough current to get hot unless it's something super-primitive like a resistor plus zener diode shunt regulator. If it is, the dropping resistor will always be dissipating the maximum power the design allows and will run hot as a matter of course. Look for big resistors that seem to be browning their nearby circuit board.
If you can't find anything that looks like it's running hotter than it's supposed to, your best bet is just to run the thing outdoors until it either settles down or catches fire. There is no virtue at all in letting the stink of hot superannuated electronics concentrate inside your living space on its way to escaping in the great outdoors.
The point about cigarette smoke is a good one. If you've been finding any tarry residues inside this machine, your alcohol swabbing will have made those somewhat more keen to escape; if the stink you're experiencing smells like twenty years of cigarette butts, it's entirely likely that that's pretty much exactly what it is.
Granted you'd only be contributing a tiny amount to the environmental load; it still fails the "what if everybody did it" morality test
Given the practical difficulty in obtaining enough decaying 1970s capacitors to supply eight billion people with the tools required to run this test, it's not really applicable.
posted by flabdablet at 9:47 AM on June 12, 2018 [1 favorite]
Audio equipment of that vintage will generally have an unregulated supply consisting of a large mains transformer followed by a bridge rectifier (probably constructed from individual diodes) and smoothing capacitors. Of these, the transformer is the only component that would normally run warm unless the amplifier is drawing enough current to heat up the rectifier, which it would normally only do when turned up loud.
Transformer windings are usually covered in shellac, and if that's starting to break down it can emit quite a sharp and pungent scent. If you're smelling something like a cheap blender trying to chew through ice at low speed, that will probably be what it is.
There might be a smallish linear regulator that provides stable supply rails for the preamp section, but I would not expect it to be drawing enough current to get hot unless it's something super-primitive like a resistor plus zener diode shunt regulator. If it is, the dropping resistor will always be dissipating the maximum power the design allows and will run hot as a matter of course. Look for big resistors that seem to be browning their nearby circuit board.
If you can't find anything that looks like it's running hotter than it's supposed to, your best bet is just to run the thing outdoors until it either settles down or catches fire. There is no virtue at all in letting the stink of hot superannuated electronics concentrate inside your living space on its way to escaping in the great outdoors.
The point about cigarette smoke is a good one. If you've been finding any tarry residues inside this machine, your alcohol swabbing will have made those somewhat more keen to escape; if the stink you're experiencing smells like twenty years of cigarette butts, it's entirely likely that that's pretty much exactly what it is.
Granted you'd only be contributing a tiny amount to the environmental load; it still fails the "what if everybody did it" morality test
Given the practical difficulty in obtaining enough decaying 1970s capacitors to supply eight billion people with the tools required to run this test, it's not really applicable.
posted by flabdablet at 9:47 AM on June 12, 2018 [1 favorite]
If you've got phenolic circuit board materials you may have inadvertently liberated some of those compounds. Traditionally the place to keep such a smelly item would be the garage but apartment living is not so convenient... In any case I would try to limit exposure to the smell.
posted by Standard Orange at 10:48 PM on June 12, 2018 [1 favorite]
posted by Standard Orange at 10:48 PM on June 12, 2018 [1 favorite]
Response by poster: Thanks for all the helpful info! It sounds like I am indeed smelling PCBs from dead capacitors along with the SRPBs all around the unit that have been saturated with alcohol. My use of a phenol-based contact cleaner (which has also soaked into a couple of the boards) has probably made things that much worse. Yikes. I won’t make a habit of doing this sort of thing in the apartment in the future. My poor cat :/
The good news is that I’ve either gotten totally used to the smell, or it’s going away on its own. Hopefully exposure to it now will at least mean less exposure over time as I use the stereo. Once I make sure no components are cooking to death (absolutely right about the power supply, btw), I’ll leave it running for a while next to the window with the fan running.
I really wish I had a dedicated workspace, but this is all I’ve got. It’s hot out, so fans are already blowing stuff out the widows as often as possible. Hopefully I haven’t shortened our lives by too much.
posted by shapes that haunt the dusk at 9:47 AM on June 13, 2018
The good news is that I’ve either gotten totally used to the smell, or it’s going away on its own. Hopefully exposure to it now will at least mean less exposure over time as I use the stereo. Once I make sure no components are cooking to death (absolutely right about the power supply, btw), I’ll leave it running for a while next to the window with the fan running.
I really wish I had a dedicated workspace, but this is all I’ve got. It’s hot out, so fans are already blowing stuff out the widows as often as possible. Hopefully I haven’t shortened our lives by too much.
posted by shapes that haunt the dusk at 9:47 AM on June 13, 2018
This thread is closed to new comments.
Perhaps leaving the stereo on with a fan blowing over/into it by a window would eventually 'bake out' the smell.
posted by pipeski at 3:45 AM on June 12, 2018 [1 favorite]