I've imported a marantz 2270 into Aus from the US that i am converting to 240v. The unit is a standard US unit that is 120v only, i have a transformer from a multivoltage 2270 that will make the conversion easy.
Theres a suppression cap across the power switch terminals marked .1+120 ohm 350v ac 650v dc. So a 0.1uf film cap with a 120 ohm resistor as a snubber. I've never had to replace one of these things before and don't know the theory behind calculating what value is needed, i presume it would depend on a number of factors such as voltage and inrush current when the unit is first switched on. Would 350v ac be enough for Australias 240v? or would i need to increase it since 240v is only an rms figure and peak to peak can be much higher. Unfortunately the switch has no markings on it either so i don't know if it is 250v rated or 120 only.
Theres a suppression cap across the power switch terminals marked .1+120 ohm 350v ac 650v dc. So a 0.1uf film cap with a 120 ohm resistor as a snubber. I've never had to replace one of these things before and don't know the theory behind calculating what value is needed, i presume it would depend on a number of factors such as voltage and inrush current when the unit is first switched on. Would 350v ac be enough for Australias 240v? or would i need to increase it since 240v is only an rms figure and peak to peak can be much higher. Unfortunately the switch has no markings on it either so i don't know if it is 250v rated or 120 only.
These are special flameproof capacitors, not regular run of the mill capacitors. I had to replace that capacitor in my revox amplifier and I took apart an old computer power supply input filter for the capacitor.
The appropriate grade of cap is called an X2 capacitor. X refers to the fact that is wired across the line (active and neutral) or across in-line switch contacts, as opposed to between the line and protective earth (chassis ground) if the appliance chassis is actually intended to be grounded. That type is called a Y cap. and requires a much higher (in the kV area) voltage rating. However, never install either type in a previously unfitted device unless you have good advice applicable to the specific make/model and don't increase the value of these caps arbitrarily.
Here in Oz, I believe the specified minimum voltage rating for x caps on domestic supplies is now simply 275V AC. as is the case now in most countries, whatever the actual supply voltage. There is a lot of difference between standard DC cap ratings and certified ones - never assume that that any old 400V- 630V cap will do. They do tend to fail catastrophically. No problem finding them, though. You can buy them in various values for different applications and note that they must be marked with the safety certifier's labels - usually printed all over the cap sides.
http://www.altronics.com.au/electronic-components/capacitors/?type_1=mains-suppression
Here in Oz, I believe the specified minimum voltage rating for x caps on domestic supplies is now simply 275V AC. as is the case now in most countries, whatever the actual supply voltage. There is a lot of difference between standard DC cap ratings and certified ones - never assume that that any old 400V- 630V cap will do. They do tend to fail catastrophically. No problem finding them, though. You can buy them in various values for different applications and note that they must be marked with the safety certifier's labels - usually printed all over the cap sides.
http://www.altronics.com.au/electronic-components/capacitors/?type_1=mains-suppression
Good bit of info here, cheers! By the looks of things the 350vac cap already fitted should be sufficient as i initially thought. The cap is placed across the contacts of the switch on this rather then across the active and neutral. Its currently fitted with an ungrounded 2 prong us cable but i will be grounding the chassis when i do the conversion.
where to host photos
If it looks like the one in the attached pic, have a good look to see if it bulged or cracked, if it is it should be changed.
rc-network-capacitors 100nF 100Ω min order of 5 a bit annoying, but... at least it won't do this
rgds
rc-network-capacitors 100nF 100Ω min order of 5 a bit annoying, but... at least it won't do this
An externally hosted image should be here but it was not working when we last tested it.
rgds
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I wonder why Rifa still keep making metallized paper capacitors (see the pic in the RS link), despite these are prone to fasil catastrophically (see your own pic).
Some decades ago, German manufacturer Wima also made encapsulated paper/foil capacitors for RFI use, called Durolit. Despite carrying the VDE sign, they also tended to fail, due to cracks in the encapsulation, hence absorbing moisture from the air. Fortunately Wima deciced to replace these by film-foil or metallized film capacitors, thus dramatically increasing their reliability.
Best regards!
Some decades ago, German manufacturer Wima also made encapsulated paper/foil capacitors for RFI use, called Durolit. Despite carrying the VDE sign, they also tended to fail, due to cracks in the encapsulation, hence absorbing moisture from the air. Fortunately Wima deciced to replace these by film-foil or metallized film capacitors, thus dramatically increasing their reliability.
Best regards!
Historically Wima made absolutely appalling capacitors - still it made repairs easy - just look for Wima capacitors, and replace them.
I used to repair large numbers of reel to reel tape recorders, radiograms etc. and while most faults were mechanical, anything else was almost always a Wima capacitor.
I once did a series of 'swaps' (back in the 70's), I can't remember what I started off with now, but basically I swapped repaired working items for faulty more expensive items. At the end of the swaps I had a motorbike, and I originally started with something that I got for free 😀 Anyway, point of this story, part way through the swaps I gained a Philips reel to reel tape recorder - unscrewed the bottom, and there was sat ONE Wima capacitor - I chopped it out, stuck a new cap in it's place, and the recorder worked fine 😀
Reliability 2 has more on the rifa/evox/kemet caps
Reading about these a while ago, it was suggested the encapsulation failed allowing moisture ingress, but they still failed safely, the newer ones are reported to have better encapsulation and most x2 caps I think have a 10ish year lifespan?
Reading about these a while ago, it was suggested the encapsulation failed allowing moisture ingress, but they still failed safely, the newer ones are reported to have better encapsulation and most x2 caps I think have a 10ish year lifespan?
only use X and/or Y rated capacitors across the Mains.
For 220/240Vac you can use X2 or X1 for Live to Neutral
and Y2 or Y1 for Live to Earth and for Neutral to Earth.
For 400Vac (3phase) use X1 and Y1
Move the snubber from across the switch (which leaves the equipment live when off) to across the load.
It's the back emf from the load that sparks the switch during the OFF movement.
The back emf current does not care what route it takes to get back to the load. A snubber across the load gives the shortest/lowest impedance route for the high frequencies in the spark emission.
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