Monday, April 1, 2013

Cleaning Audio Equipment

You really have to hand it to the manufacturers of audio equipment. People who don't know tend to think it's delicate. But in reality, if it's worth its salt, a piece of gear is built to be moved twice a day every day. Slap it in a case, grab it with a fork lift, shove it on a truck and get it to the next gig. Temperature swings, dust, moisture, pollution, it has to survive the worst and still function to spec every single time it's switched on.

Once in a while though it's good to take some time and actually maintain your gear. Just like a car, if you do nothing but put gas in it it's going to cough and die a lot sooner than if you change the oil regularly and see to all the other little things that need seeing to. Doing this for your audio gear is actually usually pretty simple. It's also pretty boring so it's good to be able to slip into sort of a zen mind state while you're working. You need to be aware enough to spot any issues but zoned out enough to keep from going insane from the sheer repetitive dullness of the task.

Take for example a relatively small cleaning that I undertook this week. I had a Presonus ACP-88 compressor that had been on duty in a rack for close to a dozen years. It's a pretty cherry spot as far as audio equipment goes. The room is temperature controlled, low humidity and the filters in the HVAC system keep everything near spotless. (It's clean enough that I don't bother to cover the console.) But in all that time the components started to suffer and the unit had become unreliable. It finally came to a head when I found out quite by surprise that it had a case fan. That distinctive sound of a tiny bearing starting to complain made it clear that it was time to get it up on the bench and do some cleaning.

Getting set up is relatively easy. You need a can of compressed air. It's better to use a bottled product than to go with a compressor unless you have a really good line dryer in place. Forcing moisture into all the little cracks and crevices isn't a good idea. A can of contact cleaner, I like to use D-5 because it's made for the task. WD-40 is good at flushing moisture and gunk out of places but it can leave a residue behind that allows more gunk to accumulate. It's better left to emergencies when you have no other options. Other than those two items all you need are some swabs, some toothpicks, some rags, and a good deal of patience.

I started out by opening up YouTube and finding a nice, lengthy concert to watch and threw on a pair of cans. With some AC/DC circa 1992 keeping me from falling asleep I pulled the top off the unit and got started. The ACP-88 is an eight channel compressor. Rather than have eight little cards in there for each channel the whole thing is comprised of two boards, front and back with a power supply in the middle. The two boards are joined by ribbon cables.

I started with the case fan. A blast of canned air got all the fuzz off the blades and got it spinning freely. Next I pulled off the two nuts that held it in place so I could get access to the bearing. A sticker covers the hole in the center of the blades. You carefully peel that back, put a single drop of 3-in-1 oil in there and smooth the sticker back down. Bolted back in place it was good as new and quiet as ever.

Next I blasted air into every place that the tiny red straw on the can would reach. A surprising number of dust bunnies came shooting out the jacks on the rear of the unit, and another unhealthy batch retreated from under all the chips on the front board. Fortunately that was all I had to do on this unit. There weren't any unreachable places and I felt like I had things pretty clean after a few minutes.

Next I grabbed the can of D-5 and sat back to start working on the jacks on the back panel. A short blast of solvent followed by plugging in a jack about ten times got things started. Then I swabbed the jack out and followed up with another short blast of D-5 to clear the contacts of any scum residue. Follow that up with a blast of canned air just to make sure all the solvent evaporated completely. Four jacks per channel, eight channels, and three songs deeper into the set list that was finished.

The front panel has five buttons on each channel. A quick spritz of D-5 into those and I cycled them each about twenty times. A blast of canned air cleared them out and then I went after the row of buttons on the back panel. That didn't take too long.

The front panel has eight knobs per channel, times eight panels. Fortunately the pots were sealed so there was really no point in trying to spray any D-5 in there. Instead I simply sat back in my chair and with the unit in my lap started to cycle each knob (two at a time) fully back and forth across their full range of movement. There's not a lot that can go wrong with a sealed pot, but sometimes a little of the resistive element will flake off and stick. Running the pots back and forth will push any crud to the ends of the path and usually leave the wiper free and clear. Some of the pots clearly hadn't been moved much in the last decade and were a little creaky to get going. I wound up doing twenty or thirty cycles on those. The more frequently used ones I did about ten cycles. When I was finished they were all moving like they were factory fresh.

One final trip around the innards with the canned air just to make sure all the solvent was gone and to try and catch any persistent dust bunnies and I was ready to put the cover back on and give the unit a test. Last thing I made sure all the ribbon cables were firmly seated and I closed the lid. I had a small mixer on hand so I plugged the laptop into that, got the signal out to the compressor and would listen to the results on the headphones.

Again it was a bit tedious as I really had to pay attention now. It wasn't a matter of just watching where the dust bunnies flew to, now it was time to make sure that all the controls were really doing what they're supposed to do. That meant testing each gate, the button that controlled the depth, and the attack and release knobs. Then on to the compressor threshold, ratio, attack and release knobs as well as the knee, auto and link buttons. Last but not least were the bypass button on the front and the +4/-10 button on the back. Those were the ones that had been giving me grief when the unit was still in service.

All told that took me over three hours and I wound up hearing not only a full AC/DC concert but also a fair amount of an A7X show too. (If I had been cleaning a console I would have had to block out two to three days.) But the payoff was worth it. When I slapped the unit back in the rack and connected it to the system every channel was back in full working order. It was like having a brand new unit. One that I can hopefully have full confidence in again. Having a compressor that's responsible for an important signal choke on you with a packed house is no fun. The sound guy is the only one scowling at the rack, everyone else is scowling at the sound guy.

So there you go. Dirt and dust are the two major enemies of equipment. They cause overheating and early demise if not dealt with. If it gets really bad the crud can actually create new electrical connections that were never intended, sometimes with pyrotechnic results. So Brethren of the Knob and Fader, it's pretty important even though it's not very glamorous to clean your gear. Perfect work for the young novice in training.

No comments:

Post a Comment

You're the Scotty to our Kirk