18 Jun
2011
18 Jun
'11
9:57 a.m.
All the PSUs that have had components pop on me have all been capacitors in
the mains filter (except the H7140 in my PDP11 but that was only after I had
been messing with it to try to fix it, so that doesn't count).
Not being an expert in electronics I am not sure of the reason for this. Can
someone explain? Is it the type of capacitor? Is that type of capacitor only
used in mains filters? If not, why have I (so far) not seen other PSU
capacitors blow up?
Regards
Rob
18 Jun
18 Jun
10:22 a.m.
They are a special type of supposedly "self healing" capacitor able to
withstand spikes without catching fire.
You would be surprised if you scoped your supply, a lot of spikes
arrive unless you filter upstream, they have a hard life.
Replace with the best you can.
Dave Caroline
1:40 p.m.
They are a special type of supposedly "self healing" capacitor able to
withstand spikes without catching fire.
You would be surprised if you scoped your supply, a lot of spikes
Be careful if ou try this. One side of the 'scope input is earthed (and
conencted to the metal case of the 'scope). Connectign a ;scope probe to
the maisn will trip an RCD if you have one, or, if you get the leads the
otehr way runnd, blow fuses or worse
arrive unless you filter upstream, they have a hard
life.
Replace with the best you can.
You can get capacitors designed for mains filtering from RS and Farnell.
IIRC, there are class X deisgned ot go between live and neutral and class
Y designed to go betwene either sideo f hte mains an earth .The latter
are specially deisnged so that they can't fail shorted, for obvious
safety reasons.
Although IU dislike 'shotgun debugging', I must admit that when one
capacitor in a mains filter circuit fails, I normally replace the lot.
-tony
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ard＠p850ug1.demon.co.uk -
dave.thearchivist＠gmail.com -
robert.jarratt＠ntlworld.com