UX8 Noise on Instrument Input 1, but not Input 2

[castlevania]

Hey everyone, I could use some help with my UX8. I notice that Instrument Input 1 is very noisy when the pad is off. The problem goes away when I engage the pad. However, this problem does not happen with Instrument Input 2. Also, on Instrument Input 1, with the pad off, if I turn the volume all the way down on my guitar, there is a strong hum. If i turn the volume up the slightest, the hum will go away. The problem does not happen on Instrument Input 2.

 

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My Troubleshooting:

I've tried multiple guitars and cables, all my gear plugs into a UPS, I've also tried to bypass the UPS. running just off of the power conditioner. The settings for Input 1 and Input 2 are set to mono, and instrument, in Line 6 Audio/Midi devices, and set to 48000hz, with 24bit sampling.

 

To be sure everything else was the same, I created a dual patch in Pod Farm, both of the dual paths having the same amp and settings, with Amp Path 1 set to Instrument 1 and Amp Path 2 set to Instrument 2. I have the pad OFF on both Inputs, with my guitar volume all the way down. If i simply move my guitar cable between input 1 and 2 on the front of the unit, the loud hum is only there on input 1.

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I don't believe the problem could be the input jack on instrument input 1, because the hum would be there with the pad engaged if it was. I'm thinking there must be a cold solder joint on the input circuit board, where there are different ground paths for PAD or NO PAD.

 

Has anyone else experienced a problem like this? I reached out to Line 6 to ask if i could buy a new input board, they are easily user replaceable. Something tells me their "policy" will force me to spend more money on a new interface. If that's the case, goodbye Line 6, hello Scarlet. However I love the UX8 and the analog VU meters, and don't want to replace it if i don't have to. That Scarlet is expensive. Help?

[castlevania]

Update: after removing the input circut board and checking resistance across ground leads, I found no issues. Upon buttoning everything back together, I found that Input 2 exhibited the same behavior. I wiggled the instrument cable at the jack inputs for input 1 and 2, and the problem comes and goes depending on which way the pressure of the cable is. Either the contact points for the jack are worn, and I can retention or replace the jacks, or I have cold solder joints. Well this is a much better outcome than i could have hoped for.

 

For the record, Line6 support got back to me and said buy a new audio interface. No thanks, jacks are $2.99 each.