thegreatroberto
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Post by thegreatroberto on Jan 17, 2006 20:07:35 GMT
 What does NPN orPNP mean when on the side of a capacitor.......Some of the caps I'm replacing in a MF Power amp have these markings.Does it mean that their polarity is not important ? Help,before I destroy something else...............I've got caps,a hot iron and I'm dangerous !
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Stormy
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Advocates putting smokers in a "Sin Bin"
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Post by Stormy on Jan 17, 2006 22:49:45 GMT
I haven't seen NPN or PNP on capacitors before... it's common with transistors, and refers to the internal structure (and correspondingly also the pinout in some cases) of the device and the order of the "sandwich" of layers it contains, with the two main materials being used called "N-type" and "P-type". As caps are also layered to some extent, could this refer to their internal structure? How many legs do these caps have?
Sorry if that was patronising!
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thegreatroberto
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The Great Roberto "himself" The real deal on a stick!
Posts: 157
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Post by thegreatroberto on Jan 18, 2006 7:57:53 GMT
Hi
standard 2 pin cap.Confused me a bit as well. I was just about to replace them with a panasonic FM and saw the npn down the side.Anyway,i put it back and left well alone!
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thegreatroberto
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The Great Roberto "himself" The real deal on a stick!
Posts: 157
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Post by thegreatroberto on Jan 21, 2006 8:51:01 GMT
Just a thought.Could they be non-polars ?There was no positive/negative on the board.If they are on the output,then they would be seeing AC....................
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Stormy
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Advocates putting smokers in a "Sin Bin"
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Posts: 153
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Post by Stormy on Jan 21, 2006 15:58:56 GMT
If they're electrolytic non-polars, they're probably back-to-back caps (ie. two polar caps wired together symmetrically in series in one casing to give the impression of one cap that works both ways around). NPN might mean that they have their anodes connected and PNP would be cathodes... Positive-Negative-Positive? I suppose they would behave differently because one of those configurations would cause each of the caps to discharge through their partner (backwards) instead of straight out of one of the leads... Do you definitely have both NPN and PNP-type caps in there? Not just one of the two?
*stops clutching at theoretical straws*
I wouldn't listen to me if I were you.
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Post by PinkFloyd on Jan 21, 2006 23:01:40 GMT
Np is non polar, safe to replace these with other Non polar types. NPN or PNP will be where the capacitor sleeve was cut ...... NPNPNPNPNP so it may show as NPN or PNP or NP NP.
What size are they, the usual MF 220uF non polars?
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thegreatroberto
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The Great Roberto "himself" The real deal on a stick!
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Post by thegreatroberto on Jan 22, 2006 9:40:57 GMT
That's the ones 220uF,10V in my Xa-s100 power amp.I'm guessing that as they are non-polar ,they are on the output side of the amp ?
I've now had alook inside all my MF gear................They must have got a cheap deal on Jamicon SK series Caps.They are everywhere.Although my X-ray CD player and my X-LP amp have another make as well.
BTW, 2 of the caps in my X-cans were shot.Both metered out at less than 20uF..........both were buldging !
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Post by PinkFloyd on Jan 22, 2006 16:05:33 GMT
That's the ones 220uF,10V in my Xa-s100 power amp.I'm guessing that as they are non-polar ,they are on the output side of the amp ? Yes, they are probably DC blocking output caps. Get a multimeter and measure the DC (if any) with the meter set to the 200mV range. If there is no offset or very little (ie: under 20mV) then it's pretty safe to remove these and jumper over the pads with zero ohm links. If you decide not to remove the output caps then you can replace them with higher capacitance varieties (220uF - 1000uF) 220uF is good but 1000uF is even better  I've now had alook inside all my MF gear................They must have got a cheap deal on Jamicon SK series Caps.They are everywhere.Although my X-ray CD player and my X-LP amp have another make as well. These are the only caps MF use, even in their mega buck equipment. They are not only cheap but they are also very nasty sounding IMO... the only reason MF employ these bastards in all their equipment is "cost" you can quite literally pick these caps up for a few pence each... replace these general purpose caps with low ESR varieties and you'll reap big rewards in the sonic department.... I guarantee it. BTW, 2 of the caps in my X-cans were shot.Both metered out at less than 20uF..........both were buldging ! Par for the course. I've seen quite a few X-Can amps with bulging caps... they normally position these 85C general purpose caps right next to hot transistors and as a result they have a tendancy to pack in pretty fast.... it's all part and parcel of the design and built in obsolescence..... 105C caps are the way to go especially in sweat boxes like the X-Can series of amps... heat is the capacitors biggest enemy so fit good quality high temperature caps that are better suited to the hot environment inside the amp. |
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thegreatroberto
100+
The Great Roberto "himself" The real deal on a stick!
Posts: 157
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Post by thegreatroberto on Jan 22, 2006 18:56:19 GMT
Thanks for that.
I checked my nu-vista pre amp................and those little bastards were in there as well.Although to be fair,beautifully laid out.
Quick question.I've noticed that in most of my amps (nu-vista pre,xa-s100 power and even my REL sub), that 6800uF caps are used in the "power supply" section.63V varieties in the 2 power amps and 100V in the pre !
Is there anything magical about 6800uF ? Or are they just a convienient size ( and cheap ).I'm considering changing the size of caps in the REL sub maybe to 10,000uF ( if I can find some !) as space is not an issue.The MF I would only change if they died, or I got really board!
Thanks
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