Help repairing Ultrasone HFI 780s -- only one driver works, non-detachable cable, no DIY experience
Nov 13, 2016 at 8:47 PM Thread Starter Post #1 of 2


New Head-Fier
Sep 30, 2011
Hi, my HFI 780s, which I've had for upwards of 5 years now, have suddenly stopped working out of the right driver. I have no idea why, and while I use them on the go and have used them outside of my house regularly, there have been no previous problems and nothing that would have reasonably caused damage, so I am assuming it is just due to normal wear and tear on the phones.
I've encountered this same phenomenon with ****ty throwaway jvc earbuds that I use at work, where one ear just randomly stops working, and from what I understand its usually the cable that causes this problem. My guess would be the 3.5mm jack or the cable itself is busted in some manner, and I would just replace the cable if it were detachable, but unfortunately it isn't, at least externally. 
I am not sure how to proceed, as I don't know how to open the headphones safely or how to do any repair on this kind of thing. Don't want to break my nice headphones even further as they're expensive and I can't afford a replacement. I'm assuming you could change the cable out by opening the left driver where the 3.5mm cable connects to the driver, but I have no idea how to access it.
Any help or guidance on how to proceed would be appreciated, if anyone knows what I should do.
Nov 14, 2016 at 5:32 AM Post #2 of 2


Headphoneus Supremus
Mar 7, 2006
First thing to check is if you get any sound or noise when you play with the cable (at the plug and beside the headphone side).
If that's the case, it's a very simple case of replacing the cable and making sure the connection stays safe.
If not, you'll need a DMM (digital multimeter) and need to open up your headphones to test that the driver still works (resistance - ohm, check). Cheap DMMs cost under $10 and you should just have one.
Let us know how these tests go and I'm sure we'll be happy to help.

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