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.
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.
Attachments
That looks more like a thermistor. That would be typical in an AC line to reduce the turn-on surge. Can you ask Opera about it?
https://www.digikey.com/en/products...eU846rC8KztfHwYmZuJzk1At7PGgLhkhoCrZoQAvD_BwE
https://www.digikey.com/en/products...eU846rC8KztfHwYmZuJzk1At7PGgLhkhoCrZoQAvD_BwE
It looks more like an inrush limiter or NTC. They often explode if they see too high current so I'm guessing something else is broken in this amp as well. I'd look for shorted supply capacitors and failed output tubes before gently powering the amp up on a variac or dim bulb tester.
I'm not a fan of leaving components dangling off the mains like that. I can't imagine that'd pass any sort of safety standard. And what's with the chassis-mounted resistor that's mounted with one screw out of two required. That doesn't exactly scream high build quality.
Anyway. Contact Opera Audio and see what the appropriate part number is for that inrush limiter. Maybe get a schematic from them if you can.
Tom
I'm not a fan of leaving components dangling off the mains like that. I can't imagine that'd pass any sort of safety standard. And what's with the chassis-mounted resistor that's mounted with one screw out of two required. That doesn't exactly scream high build quality.
Anyway. Contact Opera Audio and see what the appropriate part number is for that inrush limiter. Maybe get a schematic from them if you can.
Tom
Yikes. I didn't really look closely. Looks like there was a short to the bottom plate. Yeah, that amp needs some serious attention.
Thank you all so much for the replies. I have learned something new. This is very exciting.
I have since been googling and reading up on these thermistors.
I have checked the two items you highlighted, Grataku. The charred wire bundle you pointed out was originally right next to the melted thermistor. I pulled it aside to take the photo. I've checked the wires, only charred sheath. No exposed wires. I will rewrap them with electrical tape for good measure. The blackened second thing on the PCB you circled correspond to one of the biasing pots. There are eight of them. They all measure roughly the same between the various pins - all 4k - 6k ohms, and not shorted. So hopefully those are ok.
I will now purchase a few new thermistors to try. The links that have been provided, and all the youtube videos on the subject refer to CL40/60/70/80/90 thermistors. I can get them posted to me for sure, but the local eletronics physical store here in Australia is Jaycar. They stock a range of "epoxy dip NTC thermistors".
Like this 15ohm one here: https://www.jaycar.com.au/15-epoxy-dip-ntc-thermistor/p/RN3430
Its description says "made of a special ceramic material which changes resistance value rapidly with temperature change. They are commonly used to check thermal runaway with bipolar transistor amplifiers etc".
Its spec says Power Rating 500mW, DC current rating 250mA, 15ohms at 25 deg Celcius (room temp), thermal dissipation 6mW/degree.
Is this a correct thermistor to use? I am not sure what to make of the Power Rating and DC current rating in the specs. Are they just indicative of the power draw of the thermistor itself and the measured current when subject to a standard DC or do they actually mean this type of thermistor is for DC circuits only? My amp is rated at 100w x2 RMS so it will probabaly draw 1 - 2 amps from 240V AC, factoring in the inefficiencies.
I have since been googling and reading up on these thermistors.
I have checked the two items you highlighted, Grataku. The charred wire bundle you pointed out was originally right next to the melted thermistor. I pulled it aside to take the photo. I've checked the wires, only charred sheath. No exposed wires. I will rewrap them with electrical tape for good measure. The blackened second thing on the PCB you circled correspond to one of the biasing pots. There are eight of them. They all measure roughly the same between the various pins - all 4k - 6k ohms, and not shorted. So hopefully those are ok.
I will now purchase a few new thermistors to try. The links that have been provided, and all the youtube videos on the subject refer to CL40/60/70/80/90 thermistors. I can get them posted to me for sure, but the local eletronics physical store here in Australia is Jaycar. They stock a range of "epoxy dip NTC thermistors".
Like this 15ohm one here: https://www.jaycar.com.au/15-epoxy-dip-ntc-thermistor/p/RN3430
Its description says "made of a special ceramic material which changes resistance value rapidly with temperature change. They are commonly used to check thermal runaway with bipolar transistor amplifiers etc".
Its spec says Power Rating 500mW, DC current rating 250mA, 15ohms at 25 deg Celcius (room temp), thermal dissipation 6mW/degree.
Is this a correct thermistor to use? I am not sure what to make of the Power Rating and DC current rating in the specs. Are they just indicative of the power draw of the thermistor itself and the measured current when subject to a standard DC or do they actually mean this type of thermistor is for DC circuits only? My amp is rated at 100w x2 RMS so it will probabaly draw 1 - 2 amps from 240V AC, factoring in the inefficiencies.
The brown stuff on the PCB could also be flux. They're pretty clean elsewhere, though, so maybe not.
I don't think that thermistor is what you want. What you're after looks more like these: https://www.ametherm.com/inrush-current/standard-surge-limiter/
Maybe MS22 75004. Available at Mouser: https://www.mouser.ca/ProductDetail/Ametherm/MS22-75004
It would be better to get the right P/N from the manufacturer, though.
Note that the thermistor will get pretty hot (as in 169 ºC at the full rated current) so you need to put it in a place where it'll have some airflow. That's why it melted the wiring harness. I'd see about installing a short turret strip down by the power switch and putting the inrush limiter there. You could also add a little circuit board and use a heater winding to turn on a relay that shorted out the inrush limiter after it's done doing its thing. Then it'd run stone cold.
Tom
I don't think that thermistor is what you want. What you're after looks more like these: https://www.ametherm.com/inrush-current/standard-surge-limiter/
Maybe MS22 75004. Available at Mouser: https://www.mouser.ca/ProductDetail/Ametherm/MS22-75004
It would be better to get the right P/N from the manufacturer, though.
Note that the thermistor will get pretty hot (as in 169 ºC at the full rated current) so you need to put it in a place where it'll have some airflow. That's why it melted the wiring harness. I'd see about installing a short turret strip down by the power switch and putting the inrush limiter there. You could also add a little circuit board and use a heater winding to turn on a relay that shorted out the inrush limiter after it's done doing its thing. Then it'd run stone cold.
Tom
What Tom said. And also, as someone else said, you might need to figure out why the surge limiter failed.
Repair the melted bundle and look for any other melted wires or components. Remove all valves. Temporary replace thermistor with halogen bulb say 400W or 100W depending on size of amp. Power on and see if bulb dims after a few seconds.
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 CL60. Would all 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
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 CL60. Would all 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
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.
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.