I bought this Behringher 1602 MX 12 channel mixer nearly 30 years ago from (now defunct) venue music on bondi rd. I recorded my first and only album on it. It was the heart of my home studio for a long time. I recently pulled it out of storage only to find the left master fader was dodgy, you had to wiggle it to get a signal and every time you wiggled it, it got a bit harder to wiggle it exactly the right way to get a sound the next time.

 

So, I decided to fix it. I have a chequered history with fixing things. Sometimes all goes well and sometimes it ends up more broken then when I started. But this seemed easy enough, just replace the fader. What could go wrong?

Lots of screws to undo and not an op amp chip to be found! It is all discrete componentry. I then discovered I am not very good at unsoldering. I should have really watched the YouTube video before resorting to drilling out the solder filled holes. Only 10 pins to remove! Then, what to replace it with? I knew the dimensions and pin geometry, but what value?

Gemini AI came to the party suggesting 10kohm logarithmic linear pots. How the hell does AI know about servicing 30 year old mixing desks? this was a ripoff of a mackie mixer, which is how behringher started, so i found some mackie mixer pots on aliexpress. They were a perfect fit.

I replaced the left slider but because it was diffent to the original the L and R faders no longer physically aligned at the same volume level which offended my sensibilities so I replaced the right fader as well. I was still shit at unsoldering and when I flipped the board over I almost accidentally cut the pins of the fader I had just installer!

I cleaned all the knobs and buttons with my ultrasonic cleaner, as well as all the rusty metal washers and bolts on the input jacks. Gave the panel a good clean, put it back together , cleaned all the knobs and sliders with electronic contact cleaner so they were no longer scratchy.

Put it all back together whilst listening to my old iPod running through each input chanel. It was working perfectly, sounding great and looking brand new. I was so proud of myself putting the knobs and buttons back on. I love fixing things! When i was almost done i realized- I LOST a bloody knob!!!! Still a qualified success though! Or so I thought.... I put the metal back chassis on, hooked it up to my speakers and began plugging in devices to the input channels. Every time i plugged something in there was a loud pop, which of course i knew wasnt right but i kept going nonetheless.

I plugged in the third channel and there was the mother of almighty pops followed by a loud buzzing and then all the channel overload red leds came on. So much for my repair…

It turns out the three voltage regulators which are bolted to the side of the mixer to use the case as a heatsink need to have their legs bent 90 degrees to attach to the board but when i did so it was more of a curve which bought the legs dangerously close to the conductive metal rear chassis.

And they had shorted!!!

The question was had i destroyed the board or not? So i had to dissassemble it again , pop down to jaycar to buy a LM7815 LM7915 and a LM317. Good old jaycar still sells this stuff! I replaced them and the mixer worked good as new! They sure are robust. Anyway, I reassembled every again and its back in place in the studio again. Happy days!