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Marking is DSP 104. Green, 13mm disc with radial leads. Obviously is my problem and likely the board it was on took a transient and closed. Now just need to replace it. Cannot find anything for specs on this. Can anyone help?
In studying the circuit, it seems this component is in series from the AC input to the bridge rectifier. IE, a conducting fuse possibly. My experience with MOVs is that they usually do not have much continuity until failed which shorts them and causes a ircuit trip.
However, in this circuit, if that disc does not conduct, power will not be sent to the rectifier. I am confused...
If it's in series with the AC, then it likely is a NTC thermistor inrush current limiter. It has a relatively high resistance when cold to limit startup current, and then the resistance drops as it warms up to minimize voltage drop for normal operating currents.
Would there be any way to tell the difference? I cannot find the component data anywhere to know what it is... It had the typical signs of MOV failure with a welded hole coming out and the coating was broke in that area. I will admit that I do not know what an NTC thermistor is though.
This is an amplifier and there is a dead short somewhere. I found that little guy shorted and was feeling confident. With the bridge removed, the DC pads are at 0 ohms so that probably means we have more problems after the rectifier as well....
Maybe asking a dumb question but since I am a green horn/grunt at the EE design level, could it be that the NTC is actually the component that controls the amount of current in the entire circuit? I would sure think not, especially since there is nothing even connected to the output.
At this point, by boat is sunk because I cannot find what this component is, therefore cannot replace it since there is a huge range of values for them. Do you have any resources to search for component data?
I contacted an OEM and they thought this would be a 10 ohm, 4A NTC based on the size and application. They also indicated that there is a real problem if this thing has failed closed because they are certainly designed to fail open so transients do not make it to the bridge.
I contacted an OEM and they thought this would be a 10 ohm, 4A NTC based on the size and application. They also indicated that there is a real problem if this thing has failed closed because they are certainly designed to fail open so transients do not make it to the bridge.
Per my post in the repairs area, I pulled a pair of mosfets off that are just down stream from the bridge and there is certainly one bad one that is conducting between source and drain. I am not sure if these are typically switched in an oscillating fashion but after removing the mosfet, I now have DC side resistance in the megaohms. Just not sure if I have found all the problems yet or not...
Just a general question here, are mosfets typically switched at a certain frequency or just turned on? if that is the case, I am worried that I will be right back where i started once I replace them and power is applied...
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