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Sunfire True Subwoofer EQ power supply

 

New member
Username: Robertj2

Post Number: 1
Registered: Oct-13
My Sunfire True Subwoofer EQ stopped working. No sparks or smoke. Just no lights and non operative.

Opened up the unit and can see a blown component on the power supply board. The part is located directly next to the only fuse. It looked to be a ceramic cap or varistor...very hard material that crumbled when I went to move it. Just two solid wires remaining now and the designation "NTC1" written on the board directly under the bad part. Anyone know what this is...enough information to source?
 

New member
Username: Robertj2

Post Number: 2
Registered: Oct-13
Found a web reference for what NTC1 might designate... "negative temperature coefficient"...or more common term "Thermistor". The following description fits for the Sunfire power supply as well.

NTC thermistors can be used as inrush-current limiting devices in power supply circuits. They present a higher resistance initially which prevents large currents from flowing at turn-on, and then heat up and become much lower resistance to allow higher current flow during normal operation. These thermistors are usually much larger than measuring type thermistors, and are purposely designed for this application.

Getting closer to knowing what this part is. Sadly, tech support would not release any information to me. Said "I shouldn't be in there"...so much grief for a $2 part.
 

New member
Username: Robertj2

Post Number: 3
Registered: Oct-13
Placed a second call to Sunfire, this time to management to try to determine the part number...Manager told me they have a no parts and schematics policy and would not speak to me.

Next...contacted a local and very respected audio store who gave me some information about the role of the Thermistor and matching up the failed component. Seems that the physical size and amperage of the load are the main factors. Next, sourced a Thermistor from an online company. Ordered part number 570-1003-ND...Current Inrush Limiter 10 Ohms/8Amp Thermistor. The main fuse on the Sunfire is 6-7amps. I also ordered 2 Ohm and 20 Ohm Thermistors as alternates.

Installed the 10 OHM/ 8amp Thermistor.....works!

After 2 days of stress testing (Bass at very loud levels)all OK. I am very familiar with my music and hear no sonic changes...which is to be expected as the failed part was on the power supply and not part of the audio processor.

End.
 

New member
Username: Robertj2

Post Number: 4
Registered: Oct-13
Last post...Sunfire Sub still working fine after 10 more days of heavy listening. Hope all posts are of some help for the next user. Bye.
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