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DIY: RE20 Filter Replacement Step by Step with Photos
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BostonBassist
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#1
8th March 2009
Old 8th March 2009
  #1
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DIY: RE20 Filter Replacement Step by Step with Photos

Hi All -

I recently picked up an old neglected EV RE20. I found a lot of posts by people looking to figure out how to do this. Many just decide to send there mic in to EV (Telex/Bosch) and pay them to do it. For you DIYers, I made a slide show of how to do it.

What I do NOT show is how to clean out your old melted filter! This was a process in itself. If you really want to know some of the things I did to clean it let me know. But this one was a mess when I got it - foam melted all over and someone tried to fix the head in place with velcro! I should have recorded some samples with that though - it sounded like really bad metallic reverb. Once I cleaned and replaced the filters it sounded like new. Took about an hour to clean and about 40 minutes to replace the filters as I did this in two separate sessions - taking the mic apart and reassembling it each time.

The filters can be ordered from Telex - they may send them or they may charge you - try emailing them first and see what they say. Either way the filters are only $15 bucks shipped in US - not a bank breaker. They no longer carry the 0.025 hex wrench you need for the grill removal. Good luck finding one - the box hardware stores don't have them. I took a cheap eyeglass screwdriver and filed it down until it fit.

If you are not comfortable around a soldering iron don't try this at home! You need to desolder the leads to properly insert the body filters.

Here you go - good luck!

http://tinyurl.com/RE20FilterReplacement
#2
11th March 2009
Old 11th March 2009
  #2
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cool!
#3
11th March 2010
Old 11th March 2010
  #3
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Thanks, This was great.
#4
11th March 2010
Old 11th March 2010
  #4
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This should be stickied!

oh yes, it should.
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#5
20th April 2010
Old 20th April 2010
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Bump for a great diy!
#6
1st May 2011
Old 1st May 2011
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cocktaildrum is offline
Quote:
Originally Posted by BostonBassist View Post

What I do NOT show is how to clean out your old melted filter! This was a process in itself. If you really want to know some of the things I did to clean it let me know. But this one was a mess when I got it - foam melted all over and someone tried to fix the head in place with velcro! I should have recorded some samples with that though - it sounded like really bad metallic reverb. Once I cleaned and replaced the filters it sounded like new. Took about an hour to clean and about 40 minutes to replace the filters as I did this in two separate sessions - taking the mic apart and reassembling it each time.
Hey There,

Thanks for the photo tutorial, really helpful!

I have gone down this path with a used RE20 I picked up. I have ordered the replacement foam, and taken the mic apart.

I have cleaned out the mic case and grill no problem with a paper towel and using a toothbrush to loosen all foam. I think I will clean it with alcohol as well just to get any sticky stuff off.

What I am wondering is how best to clean:

A) The capsule, which has little flecks of foam stuck in various places plus some general stickiness.

B) the top of the lower plastic housing which is very sticky and goopy with old foam.

I figured alcohol will be safe on metal parts and even the plastic if I don't let it sit too long and if I am careful not to get it on the mic diaphragm.

I would love to here your tales of cleaning experimentation!

FYI, I also picked up a replacement screen that goes on top of the mic diaphragm, I can't tell if the old one is glued down or if that is just gunked up too. Anybody know?

Thanks!

- John
#7
29th August 2011
Old 29th August 2011
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I'm attempting to re-filter 2 RE20s, and I can't seem to remove the connector on either. I tightened the screw as far as it will go. It looks like there is a little red rim of paint (epoxy maybe?) that could be possibly holding the connector to the stem of the mic. Anyone familiar with this problem?
#8
30th August 2011
Old 30th August 2011
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I managed to remove the epoxy with acetone and a cotton swab. It is also worth noting that the threading on the screw is backwards, so to tighten it into the connector, you have to turn it counter-clockwise.
#9
9th September 2011
Old 9th September 2011
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FWIW the set screw in the top grille is

0.035" not 0.025

0.035" hex - Google Search

The adhesive found at the XLR is either EC800 or Blue barker, either of which will liquify with a solvent, iso or acetone (careful that acetone may eat some paints)

To remove the XLR the setscrew needs to go fully counter clockwise

If the XLR won't budge after solvents, it's time to get a flat head driver and a hammer and either chisel it to pieces or grab a drill and put some work to it.

A new XLR insert is ~$4 and SwitchCraft are preferred.

BostonBassist: it's very possible that the 'velcro' you found was part of the original build. I can tell by the heat shrink on the solder terminals that the unit you have is an original probably from the early '70s. They did stick 3 velcro tabs on the bottom of the element as well as 2 velcro strips parallel with the transmission tubes. They did this to seat the element in the foam more securely, though ended up omitting the velcro altogether in later revisions.
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#10
29th November 2011
Old 29th November 2011
  #10
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gshell is offline
I installed the new foam on my RE-20 last night. I used a slightly different approach that I think made putting the capsule back in place a bit easier. I desoldered the long connections from the switch/x-former unit instead of from the capsule. This allowed me to put the foam over the entire capsule and slide them into the body of the mic as a single unit.

Also I can verify that mine also had the velcro that micdaddy mentioned above.

Gary
#11
17th April 2012
Old 17th April 2012
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error_trials is offline
Sorry to bring up an old post, I'm just getting into the PL20 / RE20 maintenance arena...

My PL20 sounds fine on lower volume sources, but on a bass cab it distorts like a flappy speaker...

The foam looks OK *except* it's not positioned quite like the pictures from the original post here. The foam that surrounds the capsule comes out about 1/2" from the mic body, to the very edge of the capsule itself:



can anyone confirm that this foam is supposed to only come to the edge of the body, as opposed to the edge of the capsule?

I did order new foam to replace, so I might just trim this foam to find out.

I hope it's not a bad capsule... I'm confused that that would be it, as the mic sounds just fine at lower volumes.

thank you!!!
#12
17th April 2012
Old 17th April 2012
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Edge of body. Unless you foam is turning to dust, there is no real need to replace it. If it has started turning to dust, you might have particles trapped against the diaphragm.

Gary
#13
17th April 2012
Old 17th April 2012
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Quote:
Originally Posted by gshell View Post
Edge of body. Unless you foam is turning to dust, there is no real need to replace it. If it has started turning to dust, you might have particles trapped against the diaphragm.

Gary
Awesome. Thanks. So my foam is coming out too far (see the picture above), perhaps muffling the sound on louder sources.

From what I understand a little preventative maintenance in early foam replacement isn't a bad idea. I'll try trimming the foam back to the edge of the body and see if it sounds better, and when I get the new foam in the mail I'll either re-foam or procrastinate!

thanks again
#14
18th April 2012
Old 18th April 2012
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Hmm. nope! removed the excess foam and still get a muffled distorted bass sound with the mic when I turn up the amp (still only on '3' of the amp's volume knob).

On to taking it apart.

Anyone else had a similar problem with louder low end signals? Any solutions?
#15
18th April 2012
Old 18th April 2012
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FYI I've learned that the foam doesn't absolutely have to be flush with the mic body, it works just fine if it's extended to be flush with the resonator disc/diaphragm.

I've got it apart and have taken a look at the diaphragm, which looks as it should with no foam contamination or other problems. The bottom foam, however, is toast - it's mostly gone, with what's left turned into goo stuck to the plastic terminal block.

Hopefully new foam will solve the problem.
#16
18th April 2012
Old 18th April 2012
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Also I can confirm that the set screw is 0.035", not 0.025".
#17
23rd April 2012
Old 23rd April 2012
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Well. Put all new foam in and I'm hearing the same buzzing when I record in front of a bass cab. I've compared it to an SM57 on the same signal path, which sounded as it should, no buzzing.

I took a good look at the capsule and diaphragm, it did not appear to have any problems.. Doesn't move or wiggle freely, is positioned as it should be, etc. The resonator disk does have this fine mesh glued on, which is slightly loose in places and itself might be making the buzzing noise, but I kind of doubt the light mesh would vibrate and create that noise.

Bummer! might have to send it along to EV.

If this sounds familiar to anyone please send along any advice or condolences...

Thanks
#18
24th April 2012
Old 24th April 2012
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Quote:
Originally Posted by error_trials View Post
Well. Put all new foam in and I'm hearing the same buzzing when I record in front of a bass cab. I've compared it to an SM57 on the same signal path, which sounded as it should, no buzzing.

I took a good look at the capsule and diaphragm, it did not appear to have any problems.. Doesn't move or wiggle freely, is positioned as it should be, etc. The resonator disk does have this fine mesh glued on, which is slightly loose in places and itself might be making the buzzing noise, but I kind of doubt the light mesh would vibrate and create that noise.

Bummer! might have to send it along to EV.

If this sounds familiar to anyone please send along any advice or condolences...

Thanks
I own three RE20 microphones and one of them gets a distorted sound when using it as a bass drum resonant head microphone, the other two sound great. I did send this microphone away for a foam transplant about five years ago and when it came back, I just tested it on my voice and it sounded very nice, I didn't test it on the bass drum until I tried using it about two years ago. So I know what you're talking about but I don't want to spend tons of money getting it corrected as long as I can still you it on spoken word. The microphone was never mishandled and looks almost like new.



If anyone else has this problem, please chime in. I have the worse luck trying to get EV RE microphones repaired. It took two times back for repairs for one of my RE11 microphones. The first time it had No bottom end when it was returned to me. I had to make a comparison recording between it and another RE11 to send with the microphone the second time around. When it came back the second time, it was still bass deficient, but better, compared to my other three RE11s.

Dennis
#19
24th April 2012
Old 24th April 2012
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my re20 is seriously lack bottom... sounds filtered at aboiut 300hz....

anyone know what the possible cause is? is this common?
#20
26th April 2012
Old 26th April 2012
  #20
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hey team, just wanted to add my recent experience to the pile.

Contact # for Bosch 1.800.553.5992

Friendly and helpful man confirms foam part #'s
78231, 78232, 78233.

Bosch has a $25 minimum order, + $10 shipping.

To save me a few bucks, he directed me to these three dealers:

Full Compass - parts came to $14.70 + shipping = $23.18
Sam Ash
Guitar Center
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#21
18th December 2013
Old 18th December 2013
  #21
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Just fixed mine, thanks much for the tutorial and comments! Full Compass is the place to buy the foam parts, about half the price of buying them from Bosch, who definitely give the impression they do not want to deal with the public.
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