XR 1212 Minor Issues: Dead channel, volume LEDs

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Coelacanth
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Posts: 1
Joined: Thu Feb 09, 2023 4:57 pm

XR 1212 Minor Issues: Dead channel, volume LEDs

Post by Coelacanth » Thu Feb 09, 2023 5:22 pm

Hi All, new to the forum, first post.

I picked up a used XR 1212 powered mixer recently with a pair of nice PV115 speakers for $600 CAD. The speakers alone are $300+ each and the mixer was well over a grand, new. Although it looked to be in very good but dusty condition, I figured there HAD to be a few flaws. The seller and I did a brief power-up and test and Channel 9 didn't work.

I'm no stranger to electrical DIY work, excluding fine soldering and troubleshooting...I build custom resto-modded vintage RC cars and pretty handy with a soldering iron. I built several custom computer cases back in the day, back when computers were only beige color...custom LED and neon lighting, etc.

Anyhoo, I opened up the mixer, cleaned every single pot with contact cleaner until they all spun smoothly, cleaned a small area of dark residue from what appeared to be a liquid spill until the circuit board was looking shiny new. I put everything back together but the issue remained.

Channel 9 doesn't work whether an XLR or line mic is plugged in. More concerning though is that the "signal" light for Ch. 9 flickers, even with no mic connected, and muted. This bugs me because I wonder if signal noise will be introduced into the mix from Ch. 9 even though it's not "working".

The main mixer volume level LEDs also behave strangely, they don't seem to accurately represent the mixer volume levels. Usually they're on nearly fully lit for green, but not clipping, even with almost nothing happening or playing into the mics.

Other than those issues, the mixer seems to work quite well and has tons of power. Any thoughts on the issues? Thanks in advance!

welldigger99
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Posts: 10
Joined: Tue Apr 23, 2019 10:46 am

Re: XR 1212 Minor Issues: Dead channel, volume LEDs

Post by welldigger99 » Mon Apr 24, 2023 11:03 am

Hi Coelecanth,
I think you have the unenviable task of having to expose the component side of the channel board to carry out further diagnosis.
Not a difficult job - just time consuming removing every knob and slider!
If you are very careful, you can power up and start your diagnosis.
I am assuming you have the necessary schematic and test equipment?
If you're on a budget, use a mobile phone as your signal generator. Plenty of apps about. Headphones plugged in as normal.
My money is on one of the early stage op amps having blown, or a blown electrolytic.
With only one channel faulty you have plenty to use as a reference.
Good luck!

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