HC260C PT not starting...

[nickds1]

So. It wouldn't start.

Had a look at the start/run capacitor...

Just may have found the fault...

 

[Myfordman]

yup that is fubar. new one cheap a chips on ebay. DONT buy one as an OEM spare part.

 

[Sachakins]

Ooooooppppss

 

[nickds1]

Bought a new one from a trade supplier - only a few quid. Slightly bigger than the old but there was space for it. You can see the cavity size from the flattened bits of polypropylene that have oozed from the old cap... The grey colour is from the Al or Zn metallisation on what was once a thin sheet. I'm surprised at this failure mode as this PT only gets occasional and very light use. Polypropylene melts at between 130 and 170C, so it must have got toasty.

The old one still read 10.35uF - amazing it hadn't shorted and still had some capacitance left. The new one measured in at 30.21uF which is pretty good.

The original was from that well-known manufacturer of quality merchandise, Hang Da (*).

PT is fine now.

(*) No, I hadn't heard of them either...

 

[pe2dave]

Question: Will this type (??) of cap deteriorate with *lack* of use?
Long time back I was told electrolytics weren't happy laid unused.

 

[guineafowl21]

Question: Will this type (??) of cap deteriorate with *lack* of use?
Long time back I was told electrolytics weren't happy laid unused.

I restore the odd valve radio and reforming of old electrolytics is a common process. You are redepositing the oxide layer, which comes loose over time.

Non-electrolytics like a motor cap are built differently, so I don’t think this applies.

Contrast the OP’s experience with a cap I found in a 1950s Wolf bench grinder, A TCC ‘Visconol’, that was still bang on capacitance and showed no leakage. I assume it’s the original and is still in use.

 

[nickds1]

I restore valve radios too - and, yes, unpolarized capacitors don't need reforming.