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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB: The Classic Live Audio Board => Topic started by: Franklin Benjamin on September 01, 2011, 12:35:44 pm

Title: Corrosion on top of JBL 2426
Post by: Franklin Benjamin on September 01, 2011, 12:35:44 pm
Last night I changed the diaphragm on a 2426 and had some difficulty removing it from the driver.  I had to rotate it back and forth until it loosened up.  I also noticed that the screws that hold the diapragm down had corrosion.  Wish I had taken a picture.  The top of the driver had similiar corrosion.  I cleaned it up and replaced the diaphragm and it's working fine now. I am curious as what would cause that kind of corrosion.  The box itself is fine.  No signs of sitting in water on the inside or out.  Could a direct spill right into the horn cause something like this.  The driver is used in a wedge with foam on the inside of the grill to protect agains this type of thing.  I have had these wedges for about six years and I don't change or have a need to change diaphragms that frequently and this is the first time I've ever seen this.

Any ideas?
Title: Re: Corrosion on top of JBL 2426
Post by: Jay Barracato on September 01, 2011, 01:31:50 pm
Last night I changed the diaphragm on a 2426 and had some difficulty removing it from the driver.  I had to rotate it back and forth until it loosened up.  I also noticed that the screws that hold the diapragm down had corrosion.  Wish I had taken a picture.  The top of the driver had similiar corrosion.  I cleaned it up and replaced the diaphragm and it's working fine now. I am curious as what would cause that kind of corrosion.  The box itself is fine.  No signs of sitting in water on the inside or out.  Could a direct spill right into the horn cause something like this.  The driver is used in a wedge with foam on the inside of the grill to protect agains this type of thing.  I have had these wedges for about six years and I don't change or have a need to change diaphragms that frequently and this is the first time I've ever seen this.

Any ideas?

Most likely disimilar metals between the screw and frame as well as some trickle charge and moisture in the air.
Title: Re: Corrosion on top of JBL 2426
Post by: Stu McDoniel on September 02, 2011, 12:28:27 pm
Last night I changed the diaphragm on a 2426 and had some difficulty removing it from the driver.  I had to rotate it back and forth until it loosened up.  I also noticed that the screws that hold the diapragm down had corrosion.  Wish I had taken a picture.  The top of the driver had similiar corrosion.  I cleaned it up and replaced the diaphragm and it's working fine now. I am curious as what would cause that kind of corrosion.  The box itself is fine.  No signs of sitting in water on the inside or out.  Could a direct spill right into the horn cause something like this.  The driver is used in a wedge with foam on the inside of the grill to protect agains this type of thing.  I have had these wedges for about six years and I don't change or have a need to change diaphragms that frequently and this is the first time I've ever seen this.

Any ideas?
I have a pretty good idea of the cause.  I am assuming you are in a climate with winter.  When you take gear into a venue from a cold truck dew
forms on most everything metal including compression drivers and their insides
This causes rust and oxidation. 
The way to get around this?  Move to a year round warm climate or just deal
with winter like the rest of us do!
Title: Re: Corrosion on top of JBL 2426
Post by: Art Welter on September 02, 2011, 02:01:50 pm
As has been noted, a little corrosion is normal due to condensation.
Corrosion X is a great lubricant that can be applied to inhibit future corrosion, might be a good idea to go through your monitors, as  corrosionin the gap can destroy a voice coil (as well as sound funky).

If the driver gets beer dumped in, crystals can actually start growing, beer, stainless steel screws and the titanium diaphragm make an interesting science fair project!
Title: Re: Corrosion on top of JBL 2426
Post by: Greg_Cameron on September 03, 2011, 08:38:41 pm
As has been noted, a little corrosion is normal due to condensation.
Corrosion X is a great lubricant that can be applied to inhibit future corrosion, might be a good idea to go through your monitors, as  corrosionin the gap can destroy a voice coil (as well as sound funky).

If the driver gets beer dumped in, crystals can actually start growing, beer, stainless steel screws and the titanium diaphragm make an interesting science fair project!

Here's a corroded driver for you. JBL 2440. It was offered to me for free. I declined. I don't think any amount of work would revive it ;)

Greg