RE38 - dynamic mic troubleshooting

Hey y'all,

I purchased an EV RE38 on ebay...testing it out for the first time.  no bueno.  super thin output, nothing below ~500Hz. 

My first thought was the integrated filter, but removing that from the circuit did nothing.  Eventually hooked up the coil leads directly to pins 2 and 3, still a very thin output.

I touched up the solder joints where the red and black leads connect to the coil...that didn't help. 

At this point I've reached the limit of my knowledge about dynamic mics.  Is there surgery that can be done?  Or is my only option a call to EV? (as if there's any way they have replacement parts for this mic...haha)

(if anyone has any good links regarding general dynamic microphone repair, I'm all ears...the D12 repair thread is the best I've been able to find, but that's pretty specialized...)


thanks!
David

Sounds like you've checked all the right things, if you are certain you have bypassed the switch contacts related to the filter, then I'd call EV and see if they are of any help. 

EV was pretty helpful the few times I've had problems. They get a lot of calls about out of production mics and should be able to tell you immediately which models they do and don't have capsules for.

Dylan

If it is not electric: the voice coil is stuck. Probably the magnet has shifted.

Even when "stuck", the diaphram can make the voice coil shake a small amount. Like the teeny vibrations of treble. Not the large vibrations of bass.

Even when "stuck", the diaphram can make the voice coil shake a small amount. Like the teeny vibrations of treble. Not the large vibrations of bass.

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thank you, that is such an explanatory answer. I was having trouble understanding why it makes *some* sound, rather than no sound at all.


so is there any way to un-stick a voice coil? 

(fwiw, the voice coil measures ~360R and the humbucking coil ~10R)


here are some shots of the capsule:





it's not clear to me where the joint between plastic parts is (or, in other words, how I would dismantle the capsule further).





here's the bottom, doesn't seem to be anything of interest (what is the small brass-looking piece?):





thanks for your help!!!

I'm clueless. Talk to EV. The mike is not _that_ old.

The RE-38 mic has gone 'end of life' and there are no replacement capsules left.

While at EV I had success with a retro-fit using a similar ndym capsule found in the handheld 967. 

The magnet structure is reasonably similar, and with the existing filter network within the RE38 the resulting patterns were desirable.  One drawback is that I had to craft  the 967 head into the existing shock mt system of the 38.

The will sound similar to an RE27 using this 967 capsule.

The passive network on that mic is really neat, lots of different possibilities, like the old school 668 and similar 667a.

If it is not electric: the voice coil is stuck. Probably the magnet has shifted.

Click to expand...

Very likely, the ndym magnets are very strong and get sent into the gap.  Often from a drop.  Old epoxy and alnico are much more likely to stay home after drops.  Though not completely immune to shifting, I see faceplates and yolks shift more often than magnets in the older structures.

thanks for the info!


I received this from EV/Bosch:

Thank you for contacting the Bosch Service Desk for all your spare parts and repair needs.

I am sorry to inform you that this microphone was discontinued in 2000 and we do not offer any services on it.


Best regards

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bummer. 

I'll try taking apart the capsule...if nothing else I guess we'll have a CJ-style dissection thread.

Try carefully get the thing moving again, using it as a loudspeaker.

Having taken apart (and wrecked) a few dynamic mics, I feel your pain. They are very difficult to repair once there is a problem with the coil/diaphragm.
It looks to me like the top plastic piece has a humbucking coil and this sits over the diaphragm with the 'real' coil.
So the top plastic piece, once the wires are disconnected, probably comes off - I'd suspect is glued on.
With that off, the real diaphragm should be completely revealed.
Then the diaphragm is probably glued down at the outer edges, with the voice coil sitting down into the slot which has a magnet.