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help ID'ing a melted inline capacitor from 240V supply


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Thank you all in advance. My Consonance Cyber 880 integrated amplifier wouldn't switch on. This happened a day following 6 hours of uneventful use the evening prior. I switched it off normally. And the next day, it wouldn't power on at all. No noise, no flicker, no sign of life whatsoever.

 

With some rudimentary diagnostic skills, I eventually uncovered the culprit: it looks like there is a capacitor mounted INLINE inside the AC wire going from the power socket to the power switch. And it has melted/disintegrated beyond recognition.

 

I only know it's a capacitor because it looks round, and has a sandwitch layout when viewed horizontally. Please see the photos.

 

My question is, without having access to the wiring diagram for the amp, what would be the likely type/capacitance/voltage value of this capacitor? And what would be its purpose? It's mounted inline after the power socket, before power even reaches the ON switch.

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Edited by Jinsterrrr
accentuating the main points
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In line cap, no. A high current thermistor. They allow a slow turn on of the amp by, at turn on, offer high resistance, but quickly warmup to very low resistance. Could run hot once they have been on for a while and due to heat, age. After years will probably fail, go open. Ill see if I have some for an image.

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Another member out me onto them. The best way to use them is one in the active leg and one in neutral of the 240V inside the amp. The cheaper way, one in the active leg. I wouldn’t cover them, they may get hot if there is a high current drain. They need to cool. 

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On 17/02/2024 at 3:06 PM, mwhouston said:

In line cap, no. A high current thermistor. They allow a slow turn on of the amp by, at turn on, offer high resistance, but quickly warmup to very low resistance. Could run hot once they have been on for a while and due to heat, age. After years will probably fail, go open. Ill see if I have some for an image.

 

That was my first thought when I saw the thread title.

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7 hours ago, LogicprObe said:

 

That was my first thought when I saw the thread title.

 

Thank you so much for pointing me in the right direction, guys. I am actually quite excited to have learnt something new about amp circuit design.

 

I see you are both based in Australia. I am in Melbourne. We have Jaycar the physical store. They have these: https://www.jaycar.com.au/15-epoxy-dip-ntc-thermistor/p/RN3430

 

The 15ohms at 25deg makes it a CL60 equivalent (almost). But I am not sure what to make of the specs: Power Rating 500mW maximum, DC current rating 250mA.

 

Is this a correct thermistor to use? Or should I stick to the CL types everyone refers to?

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The NTC device that is required is not available from Jaycar.  Without knowing the original part number or access to a service manual a 25 degree rating of 10 ohms and a current surge value of 5 amps would suit as a replacement. You can order a suitable part from suppliers such as Element 14, Mouser, digikey but to avoid a minumum order charge, eBay might be a better option.

Edited by VanArn
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1 hour ago, Jinsterrrr said:

 

Thank you so much for pointing me in the right direction, guys. I am actually quite excited to have learnt something new about amp circuit design.

 

I see you are both based in Australia. I am in Melbourne. We have Jaycar the physical store. They have these: https://www.jaycar.com.au/15-epoxy-dip-ntc-thermistor/p/RN3430

 

The 15ohms at 25deg makes it a CL60 equivalent (almost). But I am not sure what to make of the specs: Power Rating 500mW maximum, DC current rating 250mA.

 

Is this a correct thermistor to use? Or should I stick to the CL types everyone refers to?

No wrong one. I left you a link use that. Or come and get one from me - Langwarrin. 

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On 17/02/2024 at 3:33 PM, muon* said:

 

Looking at this vid it appears to be a bit more to selecting the correct thermistor (for current level) as apposed to just any one will do for any amp.

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On 21/02/2024 at 2:51 PM, mwhouston said:

No wrong one. I left you a link use that. Or come and get one from me - Langwarrin. 

 

Thanks for the offer. But better if I get my own, and a few just in case whatever I put in there blows up again due to another problem that caused this in the first place.

 

The postage from that digikey website was unreasonable.

 

I ended up clicking on this: https://www.ebay.com.au/itm/1859990...qDrdFmABaVxc830XoIVusQJx35|tkp:Bk9SR5rcyfi5Yw

Hope this is right.

10DC20 = 10 ohms at 25 degrees, 20mm diameter - which I think would be good for heat dissipation

Product spec sheet says: NTC-10D20 10 ohms, 6 amp max steady state current, 0.162 ohms at max steady current, 24 mW/c dissipation factor, 113s thermal time constant

This seems comparable to a CL60. Would you agree?

I am getting this one beause of the cheap postage. Digikey wanted $25 to post a $3 CL60. This here is only $3 postage. Much more fair. Money isn't that much of issue. But the principle really annoys me. LOL

Edited by Jinsterrrr
better phrasing
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  • 2 weeks later...

Just to update everyone regarding my issue.

 

10DC20 arrived. They look just like the CL60. I soldered two of them in series and into the amplifier for an opening resistance of 20 ohms.

 

I turned on the amp and it came back to life! 5hrs of listening and no problem so far. Nothing melted or charred as far as I can see.

 

I also noticed that the volume knob was sitting at 3/4 to max. Not sure if I bumped it during all this repair process or if it was set at that level before the problem occured. I did use an SMSL-SU9 DAC with Nvidia Shield Pro as the source (Spotify). Maybe I had the source volume too low and inadvertently set the amp to 75% volume and that was too much for the amp after 10hrs driving a pair of Martin Logan Theos.

 

Anyway. Fingers crossed this is just a general deterioration of the thermistor and there is nothing else further to come out of this. Thanks to everyone who pointed me in the right direction.

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next time look up Rockby electronics,  they have thermistors and not costly at all,  they been around a long time, have moved out to a smaller place in rowville now.

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I would suggest that this was a symptom, not the cause. In your first picture there is a cable that has either burned or more likely been abraded and possibly shorted to chassis causing your problem.

The cable is the long spiral wrapped black one.

 

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9 hours ago, Batty said:

I would suggest that this was a symptom, not the cause. In your first picture there is a cable that has either burned or more likely been abraded and possibly shorted to chassis causing your problem.

The cable is the long spiral wrapped black one.

 

I noticed that first time I looked at the pic and wondered about it, but thought if it was something notable it would have been mentioned by the OP 🤔

 

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Edited by muon*
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