Repairing a Vintage Electrovoice 664 Microphone

Once you get a reputation for working and building cool things... more cool things come your way.

So, this is what happened. I helped a friend out with his computer, nothing fancy, upgraded his OS and added more RAM. Simple stuff.

He shows up with this pitted, rusted busted Electrovoice 664 and says, "I figured you could do something with this..."

Step 1: Step 1. Break It Down.

So it wasn't working. Nothing, no signal at all.

There's a screw holding the top screen on and then all the rest of the element and filters came out in succession.

Step 2: Step 2. the Parts Bin

Ok, I do a LOT of scrounging and scavenging. I don't throw much away. Anyhoo.

I had this element from a Sennheiser e835 wireless microphone. The microphone had battery corrosion issues and was destroyed. But I saved the element, the housing, and anything else that looked cool. Because you never know when I have to build another Lightsaber or SOMETHING.

Unscrew the top of the Sennheiser, and the element was sitting in a rubber isolation gasket. I cut around it to free it from the rubber cement.

Step 3: Step 3. Test Fit.

OMG, LOL and whatever else....

It FIT LIKE IT WAS MEANT TOO! Seriously. It dropped in and sat pretty. I let out a squeee!

Step 4: Step 4. Break It Down Further.

So the reason the original element was broken was mostly due to corrosion. My friend did say he found it in a pile of leaves in the back of his shed. (I want more access to this "shed")

So I took everything else apart.

Step 5: Step 5. Sandblasting

Ok, I'm not going to lie. It's cool having access to a sandblaster.

Ten minutes with some 100psi sand and it cleaned up nicely.

Step 6: Step 6. Restraint...

It was at this point I was going to paint it. Wild thoughts ran through my head of Ferrari Red, or bug yellow. Something bold.

But then I thought it should be more subtle, not call more attention to itself than it already will. Bold lines with sophisticated pizazz.

The first coat was self etching primer on the aluminum housing.

This filled in some of the pits remaining from sandblasting.

We let that dry then used a nice pewter metallic.

Step 7: Step 7. Cleaning Up Other Bits

Some light sanding took care of the rest of the grime from the screens. A combination of 600 grit sandpaper and a small Dremel wirewheel. I protected each piece with a coat of clear lacquer when done.

Step 8: Step 8. the Switch Plate

Grubby.

I scanned the switch plate, and then found an image online to guide me.

In Illlustrator, I recreated the label and printed it on some water decal paper. Fun stuff, you print it on a color photo printer, seal it with acrylic clear spray paint, cut it out and slide it onto the object after soaking the print in water. Just like old fashioned model making, putting that darn fighter jet together...

Step 9: Step 9. Circuit Test

At this point I temporarily connected things to make sure that everything functioned. Sennheiser element to switch and transformer into the cable and so on.

It worked. Cool beans.

Step 10: Step 10. Reassembly!

I soldered the wires together and used some E6000 silicon adhesive to mount the element in the housing. I used a couple of plastic pieces to hold it center while it dried.

I then cut the end off an XLR cable, and soldered it to the 4 pin Amphenol connector that fit the microphone. I could have changed out the connector, but I like the idea that the microphone is switchable from Lo-Z to Hi-Z by changing pins. Plus it's geeky cool.

Once dry, I put in the side screen, the pop screen and screwed in the center mount. I still can't believe this is all fitting together so nicely.

For a pop filter, I pulled the filter out of the Sennheiser element and cut it down to fit inside the 664's screen.