What's this surge protection component?

http://home.covad.net/~peninsula/Amp/Surge1.jpg
This is in an audio power amp, in *series* with the fuse and the mains power
switch. I've seen protection devices in parallel with the mains, and chokes in series, but I can't remember seeing a device such as this in series.
What is it? Is it (in it's former, non-crisp state) appropriate in this application? Replace with something newer/better? Remove altogether?
Thanks,
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DaveC
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It is an "inrush limiter", don't know the correct english word for it, in German it's called a "NTC", a resistor wihich will go down in its value when heated by the current flowing through it. So it has a high resistance at startup, effectivly limiting the charging current for the smoothing capacitors and transformer to something which wouldn't burn the fuse, and when heated up it is almost a short to provide sufficient current for the amplifier to operate.
If You have a slow fuse, try shorting it, if the fuse blows, You have to get a replacement for the NTC.
just my 2 cent, Michael.
P.S.Sorry for my bad English, i'm not a native speaker...
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wrote:

Michael, your English is better than that of 95% of native speakers. Useful post as well.
d
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Sorry for Crosspost, Clicked 'send' and didn'd see the Groups...
F'up to sci.electronics.components
Michael.
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On Fri, 14 Nov 2003 1:43:17 -0800, Michael Buchholz wrote

Thanks, Michael, for your reply. Very helpful.
Can someone please give me the English name for this, and maybe an on-line reference to a manufacturer or supplier?
Thanks,
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The KCC marking is for Keystone Carbon Company, now apparently part of Thermometrics. Here's the NTC page - http://www.thermometrics.com/htmldocs/numindex.htm Digikey distributes them - http://dkc3.digikey.com/pdf/T033/0821-0822.pdf
Regards, Ralph in NH
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It is called a thermistor in american circles, if that's what you meant.
They vary in size and functional parameters, so it would be hit and miss without knowing what was removed or the circuit particulars.
Mouser, and digi-key, among others, have pages where thermistors re offered.
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protection component?', on Fri, 14 Nov 2003:

'Inrush limiter' is OK.

Properly, 'NTC thermistor' NTC = Negative Temperature Coefficient (of resistance).
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Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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On Fri, 14 Nov 2003 6:32:07 -0800, John Woodgate wrote

Thanks, John.
Jameco has a list of NTC Varistors:
http://www.jameco.com/Jameco/Products/ProdCT/p091.pdf
These seem like they're transducers for measuring temperature. The specs list max dissipation as 0.55W. Seems a little lightweight for an inrush limiter. I think that they are, in this circuit, being required to dissipate much more than that.
Is this component really appropriate in this application? With the inrush current this amp has, I just have a hard time seeing any of these components handling the current.
Is there a better component? A simple resistor, maybe?
Thanks,
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DaveC
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Found this application data from a manufacturer:
http://www.ametherm.com/Inrush_Surge_Limiters.htm
and
http://www.ametherm.com/Transformer_case_study.htm
Seems that Jameco carries some of the lightweight models... The above references show specs up to 36 A.
Thanks,
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wrote:

Check also the Thermometrics line. Note that they don't really limit if you don't allow them to cool down, so a short blip in the line voltage can result in a much larger than normal inrush current surge.
Best regards, Spehro Pefhany
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this surge protection component?', on Fri, 14 Nov 2003:

Just as there are resistors (1/10 W) and resistors (100W), there are different types of NTC, with vastly different current and power ratings.

No. A resistor would permanently cut down the supply voltage to the transformer AND heat up the product.
Other posts have pointed you to more appropriate types of NTC.
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Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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DaveC wrote:

Dave,
For some good information on these devices: http://www.thermometrics.com/assets/images/cl.pdf
Both Mouser & Digikey have them. For Mouser: http://www.mouser.com / then enter current limiter in the parts search box.
For Digikey: http://dkc3.digikey.com/PDF/T033/0821.pdf
Scroll down about 3/4 of the page - you'll see Inrush Current Limiters. They have a wide range of values - you'll find one suitable for your amplifier. In the absence of any other information, select one near, (but not lower than) the value of the fuse in your amp.
A resistor is not a suitable replacement for one of these limiters. Also, while using a jumper, as was mentioned in another reply, can be a good diagnostic effort, I would recommend against leaving it in as a permanent solution.
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On Fri, 14 Nov 2003 13:03:15 -0800, snipped-for-privacy@bellatlantic.net wrote

Why is it not a good idea to leave it jumpered rather than replacing it with another NTC varistor? I know the inrush current will be high, and possibly blow the slow-blow fuse, but if I notch that up another amp or so, what's the down side? Is this too much current for the rectifier, transformer windings, etc., in the PS circuit?
Thanks,
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with
the
windings,
Yes, and to even suggest going to a higher amperage fuse to hack around this makes me wonder if you should be poking around inside it in the first place. Is it cheaper to burn down your house than to spend $2.50 on the right part?
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On Fri, 14 Nov 2003 18:25:16 -0800, James Sweet wrote

Oh, let's not get too dramatic, here, please.
Increasing the fuse might be dangerous, but it's gonna cause whatever damage while I'm standing right there when turn it on, not hours later.
Please don't dramatize and use fear-based logic just to make a point. People burn down houses using extension cords for electric heaters, not by increasing the fuse on an audio amplifier while testing it or repairing it.
But *PLEASE* let's not continue this new thread (ie, safety, etc.) here. I want to not dilute the discussion about the NTC varistor and alternatives.
If you want to continue a discussion of whether or not you think I'm sane or qualified to work on my own amp, start another thread or contact me off-line: dave-univ3660ATcovadDOTnet
Thanks,
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DaveC wrote:

Dave,
The downside is unnecessary stress on the components - diodes, xformer, caps. You could jumper it and leave it that way and run it for the next 50 years with no problems - or you could have premature component failure and be back inside the amp in the near future replacing something else. A second reason: generally speaking, if an equipment manufacturer decided to spend more money to add a part, it is probably a good idea for us to spend it when we repair the thing.
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You can use a high wattage resitor -a 100W lamp, by example- and a relay that short circuits the resistor when the power supply capacitors are charged at o near its working voltage.
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Michael Buchholz wrote:

Your English is *far* better than many of the 'native' posters seen here. fp
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