please advise how to dissolve the gunk at home (using household items, cleaning products, or something that is available at local stores).
Comment on Opened an old scientific instrument to see if it works...
fubarx@lemmy.ml 1 day ago
Protip: once you dissolve as much of the gunk as possible, take a small metal brush and give the contacts a scrub. If they’re coated, this helps open up metal contact surface to give the new batteries a chance.
But if the contacts are too corroded, you may need to MacGyver something with a soldering iron.
cordlesslamp@lemmy.today 1 day ago
Kangie@aussie.zone 1 day ago
Vinegar is acetic acid. Distilled Vinegar is quite useful as a general household cleaner.
Lemon juice contains citric acid.
CLR or a similar product that takes care of limescale (etc) is a mixture of acids.
Muriatic (another name for hydrochloric) acid is available from most hardware stores and can be used for dealing with rust.
troyunrau@lemmy.ca 22 hours ago
Mild acids that are food grade are great because you don’t have to worry about occupational health exposure. A lot of people use vinegar. I use citric acid – which you can find in the grocery store in the spices section. Citric acid is what makes sour candies sour. You buy it as a powder.
I mix a little water and citric acid and let the part soak in it, then brush with a soft wire brush (not steel wire, as it’s too hard and will scratch the parts too much).
But, as a tangent, buying stronger acids is pretty easy, depending on the acid. Hydrochloric acid is sold in hardware stores as muriatic acid. Sulphuric acid is used to recharge lead-acid batteries. You’ll have a harder time finding nitric acid (because people can make explosives with it) or hydrofluoric acid (cause it is actually deadly as fuck), but industrial suppliers often have them. I wouldn’t handle any of these without some training. Even muriatic acid will off-gas chlorine and cause all the tools in your shop to rust if stored improperly. (From experience.)
troyunrau@lemmy.ca 1 day ago
The whole battery mounting board is shot – entire traces corroded on it, and the contacts have effectively dissolved.
Fortunately, the machine was designed in 1977(ish) and batteries have gotten a lot better since. 6x AA batteries can now be replaced by a single modern 9V and it’ll deliver enough current. So I’ll mount a new 9V holder and solder it into the battery board wiring harness. I’ve already tested that solution on the breadboard and the machine appears to work.
SpaceNoodle@lemmy.world 1 day ago
9V batteries existed in the seventies. They just have far less capacity than six AA cells.
troyunrau@lemmy.ca 22 hours ago
I agree. However the Ah capacity of a modern 9V is pretty good compared to the 70s. Unless you buy the cheapest 9V crap you can find ;)
Aceticon@lemmy.world 21 hours ago
If I remember it correctly, it’s not just the overall capacity but also the how much the voltage drops as the current being drawn goes up (i.e. their internal resistance).
You can pull several Amps out of an AA without its voltage dropping significativelly though it does accelerate depletion quite a lot if you do it in a sustained way (the volage curve of alkaline batteries actually depends on how much current you draw so if you just draw at say 100mA the “knee” in the curve were the voltage drops down from around 1.5V to a value too low to be useful is a lot sharper whilst if you draw 1A it’s a lot softer with the voltage starting to sinking much sooner for the same fraction of total charge drawn).
Or in other words, the 9V battery might no be able supply enough peak current whilst still remaining close enough to 9V.
(It was actually quite a commonly reported problem in Arduino forums that people used 9V batteries for things like motors and then had weird power drops or the motors didn’t actually work as expected even though theoretically everything seems to be in spec for them)
You should probably test the device under “in use” conditions with a 9V battery rather than just in standby before you replace the current setup with a single 9V battery.