Friday, April 18, 2014

Fishman Prefix acoustic guitar pickup and over heated 9 volt batteries

I make mistakes often but usually I don't admit it. But I thought others could learn from my mistake and maybe avoid a guitar disaster. Here is my story...

I was preparing for a small gig, this usually requires replacing my strings, batteries, and tighten things down. Months if not years had passed since I changed my 9 volt battery in my Taylor 514e acoustic and since I had the battery in stock, I thought, let's be safe and change the battery. The lighting in the work room was dim as the sun was going down and I was using ambient sunlight to illuminate my small project. I didn't pay close attention to replacing the battery and since it fit in fine I (wrongly) thought I had completed that aspect of my preparation. Then I replaced my strings like I've done a thousand times before. Everything was fine and I was excited with anticipation of my fresh new guitar set up and new battery.

Now it was time for me to test out my guitar and hear the new set up. I plugged the guitar into my amp and strummed it and found that there wasn't any sound coming out of the amplifier speakers. I checked my guitar lead, the amp, made sure my pedals were plugged in and the volume was up on the Fishman controller as well as my amp. After doing some brilliant deductive reasoning, I managed to check my 9 Volt battery that was in the Fishman control panel. Here, I learned that I had a surprise in-store for me because when I touched the battery located inside the Fishman Prefix control unit, I found that the battery was heating up - That heat or condition is called Thermal Runaway. My mistake was that I installed the 9 volt battery in backwards where the battery negative side was in contact with the Fishman controller positive side.

It is difficult to clearly see the polarity signs - Even with a flash!

I broke some of my own rules during this set-up. The following are a few common sense rules to follow.

  • Always have a Battery powered flashlight handy and use it to illuminate things you cannot see well.
  • Never put in a battery without being overly cautious about the proper polarity.
  • Make sure the battery is new. Buy batteries from a store that had high traffic.
  • Make plans and prepare in advance so that you will have enough time to do a proper set-up.
Which side is positive or negative? Use a flashlight to help you see your work piece.

Lastly, I generally prefer acoustic guitars without pickups because  when recording there is no substitute for a high end external condenser microphone by Neumann or AKG. However, if I must use an on-board pick up, I prefer a unit that leaves the guitar body unmolested or without holes. The pictures on this page are of a Taylor 514 circa 2000-2001 and it's a fine instrument and the Fishman does work well, so well that I prefer it to the newer electronics on the latest Taylor Expression system.

In conclusion, if your battery is heating up then it is extremely probable that you have installed it backwards!  Learn from my mistakes and be cautious when installing batteries in anything!

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