Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on June 24, 2012, 03:08:43 pm
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(http://img-europe.electrocomponents.com/largeimages/R209213-06.jpg)
http://it.rs-online.com/web/p/reti-capacitive-rc/0209213/ (http://it.rs-online.com/web/p/reti-capacitive-rc/0209213/)
https://docs.rs-online.com/e612/0900766b81717851.pdf (https://docs.rs-online.com/e612/0900766b81717851.pdf)
https://docs.rs-online.com/145f/0900766b8171cb57.pdf (https://docs.rs-online.com/145f/0900766b8171cb57.pdf)
https://docs.rs-online.com/47e6/0900766b815a454d.pdf (https://docs.rs-online.com/47e6/0900766b815a454d.pdf)
Do you think that this component can solve switching pop problems ?
the body in the photo is labeled 250V~, don't care, specs report 630V DC
K
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If you read all the details, it's a class X2 cap.
Class X caps are rated to be connected from hot to neutral, or across the line. If you will connect the cap from a high voltage point to ground (or the chassis), you ideally will get a class Y cap. They are rated for connection from either line to ground.
Either way, the point of class X and class Y caps is that they will fail safely, if they fail.
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So seems that this in series resistor + cap is a good component to try
Thanks HBP
K
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Def post results! On my latest build I do not have any discharge noises from the caps when I switch to standby or power off. The only noise I get is a little "bump" when going from standby to play. It's totally livable, though it would be nice to have silence.
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I put a 0.047uF cap and 220K resistor across the standby switch. Got the idea from Merlin Blencoe and Ceriatone. It's totally silent and you don't need a fancy class Y cap for it. The resistor put a little voltage on the caps, and reduces the inrush current a bit. I have 70V on the caps with the standby switch open.
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I put a 0.047uF cap and 220K resistor across the standby switch.
The component is build exactly to do that, more it is an X2 cap (as HBP pointed) and the price is affordable
http://www.kemet.com/Lists/ProductCatalog/Attachments/146/F9000_GenInfo_RCUnits.pdf (https://www.google.it/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CDMQFjAA&url=http%3A%2F%2Fwww.kemet.com%2FLists%2FProductCatalog%2FAttachments%2F146%2FF9000_GenInfo_RCUnits.pdf&ei=QVxsVLuQH4XkaI6_gLAI&usg=AFQjCNGmcDx1Ddst7nZnNaEZOc7n4mxzSA&bvm=bv.80120444,d.d2s)
K
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I put a 0.047uF cap and 220K resistor across the standby switch.
The component is build exactly to do that, more it is an X2 cap (as HBP pointed) and the price is affordable
http://docs-europe.electrocomponents.com/webdocs/073b/0900766b8073b055.pdf (http://docs-europe.electrocomponents.com/webdocs/073b/0900766b8073b055.pdf)
K
OK sorry. My cap and resistor are in parallel, across the switch. I thought X2 caps were only used between the chassis and dangerous voltage. Couldn't you get a better, cheaper cap, with a higher voltage rating, without the X2 rating? Just curious.
Thanks
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OK sorry.
there is no reason for an apology, all is fine :smiley:
The component can be used also in other way, between hot and ground as it fails safe, the price isn't very high, so I've think to give it a try
K
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The caps which are rated to be connected to a power line (as in an EMF filter for the cord coming from your wall outlet) are Class X and Class Y.
EMF filters are often designed such that there are caps connected from hot to neutral (across the line), and from each hot and neutral to ground wire.
The Class X caps are rated to be connected "across the line" from hot to neutral. Class Y caps are rated to be connected from either hot or neutral to ground. The easy way to remember is "X" = "across".
Resistors most often fail by becoming open circuit. Caps most often fail by becoming a short-circuit; they generally leak current and act as a poor short circuit before actually failing.
The point of class X and Y caps is that they are designed to fail in a safe manner, and become open circuit. You shouldn't even know they've failed except for perhaps more noise in the case of an EMF filter. Now really, a 600v cap in a 120v circuit should live a very long life, but if they did fail (in something other than being across the standby switch), you hope they only pop a fuse.
Fortunately, in the case of the standby switch, cap failure probably only means the switch will appear to not put the amp on standby.
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OK sorry.
there is no reason for an apology, all is fine :smiley:
The component can be used also in other way, between hot and ground as it fails safe, the price isn't very high, so I've think to give it a try
K
Thanks, Kagliostro! No worries :icon_biggrin:
Thanks HBP for explaining the X/Y capacitor classes!
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I've always just put a 47uf from the standby to ground. Works fine and I have never had to replace one. Am I missing something here? I get no pop.
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I've always just put a 47uf from the standby to ground.
OK you are lucky
However consider, at least, to have a fuse on your B+ rail, just as prevention
K
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I've always just put a 47uf from the standby to ground.
OK you are lucky
However consider, at least, to have a fuse on your B+ rail, just as prevention
K
No, I was asking. I use circuit breakers, not fuses. Also, if it calls for a 3 amp slow blow, I use a 2 amp breaker. On the B+ I use a .5.
What I was asking is what does the resistor do (I know what resistors do) in this location. It is just the slowing of the current to the B+? Do you see a voltage drop from your standby lug and the first node.
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I'm not sure to understand well your question
However as the resistor and the cap are in series and connected in parallel with the standby switch they will not affect B+ voltage
K