# How do I figure out what's wrong with my crossover?



## dannieboiz (Apr 18, 2010)

I have an NHT crossover that seems to be stuck at one frequency all the adjustments seems whack, Is there an easy way to find the defective component with a multimeter?


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## lcaillo (May 2, 2006)

I am not familiar with your unit, but the answer is probably yes. One would have to have a schematic or some idea about the circuit design and then test the appropriate components. Do you have a schematic or circuit diagram?


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## dannieboiz (Apr 18, 2010)

The SubOne has an external controller which I think is where the diffuclty comes in. It consist of the volume, gains, filters and phase selection. Finding the schemetic for this would probably be impossible.


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## lcaillo (May 2, 2006)

Have you contacted NHT or looked on their site? 

The circuit is likely not much more than power supplies to several op amps with associated caps and resistors. Adjustments are typically made by varying resistances in the circuits with potentiometers and swtichable resistive networks. Not much to troubleshooting these things if you have some skills. The parts are usually very generic and cheap. Labor can be another matter. Even without a schematic you can usually sort it out with pin out diagrams of the active devices.


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## dannieboiz (Apr 18, 2010)

I'm thinking of opening it back up and test each resister and capacitor to see which one is bad. But I remember that it has to be desolder before testing, no?

I'm looking on NHT website at the moment, my next step is to contact them but aren't the schemetic propriertary stuff?


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## lcaillo (May 2, 2006)

These kinds of circuits are often so generic that they are not concerned with someone copying the design. Many are little more than implementations of the application examples provided by the maker of the op amps in the unit. Some companies will make the schematics available if you just ask.

You can measure some components in circuit, but it depends on the circuit and what you are trying to measure.


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## dannieboiz (Apr 18, 2010)

Thanks for all the help Leonard, looks like NHT do publish their schematic on their site. The SubOne however is vintage so it's not there. I just emailed them for a schematic, hopefully they have one. I'll post a reply on the progress.


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## lcaillo (May 2, 2006)

It is right here:

http://www.nhthifi.com/ServiceCenter/Tech-Docs


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## dannieboiz (Apr 18, 2010)

I can't believe I missed that. LOL now I gotta figure out how to read it.


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## lcaillo (May 2, 2006)

If you can't figure it out, and you can't find someone locally to do it, contact me by email. The repair should be rather simple and the unit should not be expensive to ship.


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## dannieboiz (Apr 18, 2010)

Cool, I'm reading only on how to read the components, you're correct about not having much components, just resisters and capacitors. I'll test each component to see which part is bad. If all else fails, you'll hear from me.


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## dannieboiz (Apr 18, 2010)

I went through and tested all the resistors and found 4 bad ones.

R81-100 
R53-100k 
R60-1k
R8- with only one black bars which is supposed to represent 1? I'm unable to find this on the schematic either which is strange.


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## lcaillo (May 2, 2006)

Unusual to have 3 resistors bad, and if any failed they don't do so by themselves.


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## dannieboiz (Apr 18, 2010)

Interestingly enough, when I removed R53 and tested it again it measured ok. Then I discovered that you can't always test resistors on the board. DUH!

I resolderied in and went through all the contacts and make sure they're good. Out of curiousity I hooked it up and it was playing again. Now, it leads me to believe the 8pin din cable is bad.


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