EV RE20 "Babby Rattle" Repair

Discussion in 'Recording Studio' started by kfowler8, Feb 14, 2017.

  1. kfowler8

    kfowler8 Senior Member

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    Piggybacking off my other thread, I wanted to start a new one detailing this repair. Seems to be a lot of interest in fixing this issue so I thought it would be helpful to show a detailed process.

    I picked this mic up locally knowing it had this issue. I paid $150 taking the chance I could fix it. This could be a huge win for a great mic if this works. As I write this, I'm only half-way through the repair. I'm not 100% sure this is going to work. I feel good about it though. We'll see.

    WARNING!!!!!

    This repair is not for the feint of heart. It's been described as brain surgery. I've never done brain surgery but it's probably pretty close. It's really easy to make the mic inoperable. So what should I attempt this? Well if you really want your mic to be usable, you have nothing to lose. It's $230 to ship it back to EV and have them fix it. Include shipping for the return. EV said you're basically getting back a brand new mic. The only part they reuse is the exterior housing.

    The Problem

    This is a common issue with this mic. When you shake it, you can hear something that sounds like a baby rattle. Something inside is loose. This can be caused by two issues. One's a heck of a lot easier to fix.

    One problem is the interior foam degenerates over time. It basically falls apart. This causes the capsule to bang around inside the housing. This fix is not too bad and only requires some de-soldering. You can order the replacement foam from Full Compass.com. There are three parts you need. It's like $21 including shipping. Unfortunately that's not the problem we have here.

    The second common issue is where a plastic disk under the diaphragm becomes unglued and rattles around. I'm sure using the mic on a kick drum accelerates this issue. Rattle can be picked up on a recording which makes the mic pretty useless. This is the issue we have here.

    Stay tuned. Lots of pics coming.
     
  2. kfowler8

    kfowler8 Senior Member

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    So here's our subject.

    [​IMG]

    Not sure if this is going to work but here's a video of the rattle. Check it out.

    Baby Rattle Syndrom

    First step is to remove the top casing. There's a tiny allen screw you can see in the pic on the left. It's real small. Like flea size. The size is 0.035". I used a micro screwdriver and it worked fine. It's also possible that there some glue on the threads so when you turn the head and it doesn't budge, you may want to gently use a heat gun.

    Now, I think it may actually be possible to go directly to repairing the disk without disassembling the rest of the mic. There's some slack available between the mic element and the control base. So if you pull on the top of the mic, the element should come out some before you run out of wire. That being said it would be real PIA to work on it like this. I fully disassembled mine.

    Next we move to the XLR jack. There's a screw on the top that you need to turn counter clockwise. Turning it this way actually drives the screw deeper into the jack. This is what you want. There's usually some red glue (it's actually silicon sealer; Thanks Darrell!) on the jack. You can see it in the pic below. You'll want to use either some acetone on a q-tip or a heat gun to loosen the jack. I used both. Try using a heat gun while pulling out on the jack with some needle nose pliers at the same time. If you destroy the jack, don't worry. It's a cheap replacement part. Take a good note of how the green and red wires are connected.

    After this, de-solder the red and green wires from the jack.

    [​IMG]
     
  3. kfowler8

    kfowler8 Senior Member

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    Moving on. If you look at where the XLR jack was inside, you'll see a normal size allen screw. I can't remember which size but it's nothing unusual. Unscrew this all the way out and place to the side. This is what connects the base to the rest of the mic. The base comes off and you should be looking at this and this. Note which holes the wires are running through.

    [​IMG]
    [​IMG]

    Are we nervous yet? This is all the easy parts.
     
  4. kfowler8

    kfowler8 Senior Member

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    Next unscrew those three silver screws holding that Y looking metal piece. Note of the screws is holding a ground lead down. Place the screws and the Y metal piece to the side.

    You should now be looking at this:

    [​IMG]

    Note that there's a copper screw the holds the switch down. It's removed in this pic but you can leave it in. You don't need to remove it.

    You can see where your green and red wires that ran to your XLR jack are connected. Leaves those alone.
     
  5. kfowler8

    kfowler8 Senior Member

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    There are two wires that need to be de-soldered here. The blue and the black wire. There's also little back shrink wraps on the wires to help keep them neat. These slide right off.

    [​IMG]

    The black, blue, and main ground wire that was screwed into the metal Y piece run through the center hole and all the week to the element. Pull the black control piece towards you. It starts to get real tight when it gets close to the edge. Keep pulling. It'll come out. Try to keep the blue, black and ground wires in the middle.

    Once the black piece is pulled out, you're going to see a bunch of wires on the underside of it. You don't need to de-solder any of these. Just place it to the side.

    You should now be able to pull out the entire element which should be encased in foam. Slide the foam off and put it aside.

    You should be looking at this:

    [​IMG]

    [​IMG]

    There's a cover over the diaphragm held with two screws. You'll want to remove this. The screws may be hidden under the mesh.

    [​IMG]

    Brain surgery is next
     
  6. kfowler8

    kfowler8 Senior Member

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    Here's a good look at our culprit. The black disk is loose. Kind of looks like an eyeball.

    It's a good idea to make two marks on the silver disk and brass mount. This way you'll know how to orient the disk when you put it back on. Make the two marks on the same side. I used a permanent marker in the pic.

    Those red lines are really thin magnet wires. They're actually on the outside of the diaphragm and then run through the holes. They're very fragile. This is what we're to be working with.

    [​IMG]

    The two magnet wires are attached to two pole pieces on each side. You can see them in the pics below. Note they're the really thin wires, not the larger ones. You should see some slack before they're soldered to the post. Pry the wire up a little so you can handle it. Warning it's probably going to be glued down to the base as well.

    Here's a bunch of close ups.

    [​IMG]
    [​IMG]
     
  7. kfowler8

    kfowler8 Senior Member

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    I used a solder sucker to remove as much of the solder as I could. I also used the solder iron to melt the glue so the wire would come free from the base. I could never find exactly how the wire is attached to the post. It almost looks like it runs under the mount.

    What I ended up doing was taking a scalpel and actually cutting the wire right at the post. You should be able to get really close and have plenty of lead left to re-solder it back to the post. Straighten the magnet wires so you can get ready to pull the disk off.

    Here's each side:

    [​IMG]

    [​IMG]
     
  8. kfowler8

    kfowler8 Senior Member

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    Removal time. This is tricky. You can very easily crush and break the magnet wires here. This is what worked for me.

    First, score the metal disk between the brass base. Mine had glue all over the place. See the slot to the left of the black mark. There's one on each side. Take a flat head screwdriver and turn it 90* so the disk lifts up. Leave the screwdriver there. Go to the other side and use another screwdriver to lift the other side. Mine came off pretty easily. It's going to want to pull back to the magnet. Now grab the disk and pull straight out so the wires come out through the hole. Hold your breath! Note which holes the magnet wires came out of.

    [​IMG]

    This is now what it should look like. This was a really poor design by EV. I can't believe they couldn't find a better way to secure the disk to the magnet. This is as far as I've gotten. I plan on re-gluing the black disk tonight. Getting the metal disk back on the magnet without crushing the magnet wires will be tough.

    [​IMG]

    [​IMG]
     
  9. DarrellV

    DarrellV Derl Ver.... ERMAHGERD!.........It's a Nerlin! Silver Supporter Premium Member

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    Hope this helps....

    [​IMG]
     
    Last edited by a moderator: Apr 23, 2017
  10. kfowler8

    kfowler8 Senior Member

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    Yup, got that. It's good base diagram but doesn't give you a lot of inner workings. Helpful though.
     
  11. kfowler8

    kfowler8 Senior Member

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    I may have hit a snag. I glued the disk back on last night with the plastic epoxy. Seemed to work really well. Strong bond.

    I carefully fed the magnet wires back through the holes and onto the magnet. This actually was easier than I expected. I let the disk pinch my fingers so I control the placement.

    Here's where I ran into trouble. I had a really hard time soldering the magnet wires back to the posts. It's like the wire has some kind of coating on it. When I thought I had a decent weld, I reassembled the mic to test it out.

    It works, sort of. All of the bass is gone. It basically sounds like you're talking in a tin can or from some really old voice recording. EV said this would probably be what it sounds like.

    Any ideas what the issue may be? If the two magnet leads aren't connected, will the mic still work? If so, this would tell me that my issue is with the solder joint., I did find out you don't have to disassemble the whole mic to get at the element. There is enough slack to get at the magnet wires.

    So things don't look good at this point. There are couple more things I'm going to try but I'm not hopeful. May have to send it back to EV.

    Open to any suggestions.
     
  12. DarrellV

    DarrellV Derl Ver.... ERMAHGERD!.........It's a Nerlin! Silver Supporter Premium Member

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    Hey Kev, the magnet wire is enamel coated. You cannot solder directly to it.

    It can be gently scraped with a sharp blade or gently and quickly heated with a small lighter flame to burn the enamel off of it.

    A light sanding (or scraping) and you should see bright copper which will solder.

    Be sure to check the centering of the voice coil in the gap so nothing is rubbing.

    Check your lead connections to the transformer per the diagram I put here yesterday.

    The tinniness sounds like a mismatched transformer hookup creating unbalanced or out of phase signals.

    I also found 2 sources for replacement guts if you need them. It's the whole 3 rod assembly but no case or foam.

    Keep us posted!
     
  13. kfowler8

    kfowler8 Senior Member

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    Thanks. I'll check that. Full Compass has replacement guts but it's like $270. EV will basically be giving you a brand new mic expect for the housing for $230.

    Being out of phase is exactly what it sounds like now that I think of it.
     
  14. DarrellV

    DarrellV Derl Ver.... ERMAHGERD!.........It's a Nerlin! Silver Supporter Premium Member

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    Was thinking too about the gap from the disk to diaphragm. Does it look the same? Is there a similar air gap in there between them now?

    Wondering because you stated EV knew this would happen.

    Makes me wonder if they slightly pressurize the capsule under the diaphragm and then seal it to create an air cushion under it?

    This would effectively lift the diaphragm slightly and create an 'acoustic suspension' under it.

    Would also give the mic a different sound and response, as well as an 'air spring' cushion to help absorb loud impacts.

    Wild imagination, I know!
     
  15. kfowler8

    kfowler8 Senior Member

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    I suppose that's possible. To me it looks the same. Hard part about doing this is I don't really understand how the whole thing works in the first place.

    I've got a couple of ideas to try and troubleshoot the problem. I'd like to isolate it if possible.
     
  16. rabidhamster

    rabidhamster Senior Member

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    Photos aren't showing but it's a cool thread
     
  17. kfowler8

    kfowler8 Senior Member

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    Hmm. Darrell can you see the pics?
     
  18. DarrellV

    DarrellV Derl Ver.... ERMAHGERD!.........It's a Nerlin! Silver Supporter Premium Member

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    No, they disappeared yesterday and I thought it was me.

    I've been beating up my firewall but nothing.

    Did your source share go private on you?

    Happened to me once here, changed from public to private. Shut everyting off, but I could still see them on my side.
     
  19. DarrellV

    DarrellV Derl Ver.... ERMAHGERD!.........It's a Nerlin! Silver Supporter Premium Member

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    I've got answers coming for that. And diagrams.
     
  20. kfowler8

    kfowler8 Senior Member

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