Author Topic: Capacitor Identification  (Read 805 times)

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Offline Sparky49Topic starter

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Capacitor Identification
« on: April 26, 2020, 04:56:07 pm »
I'm replace a few capacitors from a bit of gear made (I think)  in the 60s. However I'm having some uncertainties about certain capacitor values as I cannot find any schematics for this instrument on the internet (Advance Instruments TC9 B/S). Would anyone be able to check my assumptions for the following capacitors please?

The first is in series with the signal input - I'm guessing this is a 0.15uF 400V capacitor - but I'm not familiar enough with the different cap types to know if it is paper/polystyrene/whatever. What would be a good substitute here?



The second picture shows a large green capacitor on the main board for the nixie tubes. Initially I presumed this was a 4.7 mF capacitor (4700uF), but my LCR meter measured it as 4.9uF, so now I am assuming this is 4.7uF. I also assume this is for 160V, but please correct me if I'm wrong on this too.



Finally there is this arrangement on the mains input. I presume this is a 5000 pF capacitor - for 3000V? I'm not sure what the yellow component is - it has DCC TYPE 666 1 AMP 6937 written on it.



Here is the schematic of the two lots of this components - I presume it is a mains filters, so the yellow component is an inductor of sorts. Any idea for value?



 

Offline octillion

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Re: Capacitor Identification
« Reply #1 on: May 01, 2020, 03:23:32 am »
The first capacitor is some sort of film, 0.15 uF 400 V.  No need to replace it if it tests good (film don't tend to fail with age).

The second is 4.7 uF 160 V.  On old capacitors/documents "MFD" means micro-Farad (uF), and MMFD is micro-micro-Farad (pF).

The third is 5000 pF 3 kV ceramic capacitor, used for RFI suppression if it is placed across the line and ground.  No real need to replace if it tests OK, but you could replace it with a modern Y-class safety capacitor.  The yellow thing is seems to be heat shrink over a 1 A fuse.
 


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