Jaybee24":mbts7rei said:
All types of capacitor can be sourced from a firm called "RadioSpares" They are mail order or deal over the counter
Sounds like you're as old as me! My dad used to sit me on their trade counter (in West London, I think) when I was four years old, back in the <cough>...
... But they haven't been Radiospares for decades. rswww-dot-com will get you there (replace the dot, obviously), but if you don't work with electronics it's a bit daunting. You might have more success with CPC, who are the 'retail' arm of Farnell electronics (RS' main competitor). Google them for a URL.
You need:
-- a 'stud-mounting', 'starter' or 'motor control' capacitor (probably unless the motor has a clip or the cap mounts inside the connector junction box),
-- the correct voltage rating for your setup (usually 240V), same-as or higher will do (but higher voltage will be physically bigger, probably),
-- the correct value - you mentioned 40uf ("microfarads").
Capacitors for electronics come in 'standard values' so that designers can can make up the exact values by combining them in series or parallel. This doesn't really apply here, but it does mean you might only see 47uf or 33uf (standard values), and not 40 (not commonly stocked). If you're lucky you might see 39uf. I'd probably risk a 47uf one as its slightly closer than 33.
Depending on the circuit, the stud (if fitted) provides deliberate earthing for the metal can of the capacitor which is to improve the screening and thus the interference the motor emits. Check the original, and match the new one as much as possible in this regard.
One final point, modern capacitors tend to be physically more compact than designs of say 20 years ago. It's a bit of a nuisance when revamping hi-fi, as things don't fit in the mountings (but it's better than being too big, I suppose). So if you do order one and what you get sent is significantly physically smaller, that isn't necessarily incorrect. As others have said, the voltage is important (to stop the new one emulating the old one!).
HTH.
Caveat: I'm not an electrical engineer either, but this stuff isn't too hard if you're careful (and you do need to be). There's loads of information on the net, including the very good motor tutorial on this site.
