What's this surge protection component?

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...

Michael, your English is better than that of 95% of native speakers. Useful post as well.

d

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"Michael Buchholz" schrieb:

Sorry for Crosspost, Clicked 'send' and didn'd see the Groups...

F'up to sci.electronics.components

Michael.

On Fri, 14 Nov 2003 1:43:17 -0800, Michael Buchholz wrote (in message ):

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,

I read in sci.electronics.design that Michael Buchholz wrote (in ) about 'What's this surge protection component?', on Fri, 14 Nov 2003:

'Inrush limiter' is OK.

Properly, 'NTC thermistor' NTC = Negative Temperature Coefficient (of resistance).

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

On Fri, 14 Nov 2003 6:32:07 -0800, John Woodgate wrote (in message ):

Thanks, John.

Jameco has a list of NTC Varistors:

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,

Found this application data from a manufacturer:

and

Seems that Jameco carries some of the lightweight models... The above references show specs up to 36 A.

Thanks,

are you talking about a resetable fuse? Raychem is one manufacturer followed by many others. rw

"Rein Wiehler" schrieb:

No, I meant replacing the NTC thermistor by a piece of wire , but this only works if the OP has a slow fuse in the Utility panel, otherwise this fuse will blow due the inrush current not longer being limited.

Michael.

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

It is a NTC - Negative Temperature Coeffiecent resistor.

sells them. Also note there are many sizes - you have to match them to the current drawn through it.

In English it's called an NTC, because that's an acronym for Negative Temperature[Thermal] Coefficient [resistor].

The KCC marking is for Keystone Carbon Company, now apparently part of Thermometrics. Here's the NTC page -

distributes them - Regards, Ralph in NH

I read in sci.electronics.design that DaveC wrote (in ) about 'What's 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.

Dave,

For some good information on these devices:

Both Mouser & Digikey have them. For Mouser: enter current limiter in the parts search box.

For Digikey:

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.

On Fri, 14 Nov 2003 13:03:15 -0800, snipped-for-privacy@bellatlantic.net wrote (in message ):

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,

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?

On Fri, 14 Nov 2003 18:25:16 -0800, James Sweet wrote (in message ):

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,