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Dirty-South Blues Harp forum: wail on! >
Weird harp mic element problem
Weird harp mic element problem
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bluzmn
40 posts
Aug 10, 2011
3:48 PM
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I was rummaging through a box of junk last week, and I came across a box labelled "crystal element PMC 151". Sure enough, it was an Astatic MC-151 element. I figured it was the one I had removed from a Hohner Bluesblaster someone had given me 15 years ago because it was allegedly broken, but I hooked it up to a guitar cord with some alligator clip jumpers and plugged it in to a tiny solid state Harmony practice amp I had anyway (it was 4 in the morning). It screamed like a pig; I turned down the volume, spoke a few words, and it worked!
I have a JT30 with an MC-127 element that's dying, so I decided to put this MC-151 in that shell. I removed the MC-127, grounded the shell (it had never been since I bought it), installed the MC-151, and tried it out; it didn't work. I tried reversing the leads; it didn't work. So, reluctantly, I put the MC-127 back in; it worked, so I hadn't wired any thing wrong, plus it no longer hummed. Just for the hell of it, I hooked the MC-151 back up to a guitar cord with alligator clips jumpers;"testing,1,2,3," it worked! I cupped it and played some harp through it; it worked! Does anybody know what the hell is the problem?
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chromaticblues
962 posts
Aug 11, 2011
6:24 AM
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Don't ground the shell. If you look close you can see which one is for ground and which is not. The ground lug will have a little isolation ring that looks like a washer. solder that to the shield of a high impedence chord and the other lug to the wire in the middle. There should only be one wire in the middle and the shield.
Hope that helps.
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rharley5652
556 posts
Aug 11, 2011
5:01 PM
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Bluzmn,. "The ground lug will have a little isolation ring that looks like a washer."
INCORRECT,..
That lug with the washer is your Hot lead,..The Lug that is soldered to the shell itself is your Ground lead,. And yes Do ground the Mic shell also,.
see pic of MC-151c
------------click Link Below -----------
Simply Unique Kustom Mic's By Rharley
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bluzmn
42 posts
Aug 12, 2011
8:12 AM
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I've wired the element into an old shell and found that the problem is that this element cuts in and out intermittently. It will be playing along beautifully (and it does sound glorious), and then will cut out for no apparent reason. It my come back on in a few seconds, and it may not. I have found that when you are having this sort of problem with an electrical device, it indicates that there is a loose wire inside somewhere. Is there any way that I can open up an MC-151 element without destroying it?
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Greg Heumann
1210 posts
Aug 12, 2011
10:14 AM
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@bluzmn - you can't open up the crystal (without a very high chance of destroying it. I've opened a lot of dead ones and there are no wires to repair - everything is connected via thin brass ribbon, very delicate. It is hard enough to open them - but getting them back together is even harder - as you will have to destroy the crimped-over portion of the casting that is holding the edge of the diaphragm in place. One of those connections is dying - which pretty much means the element is toast. You might find that drawing hard, or blowing hard - brings the problem on - due to the relative change in position of the diaphragm
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/Greg
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rharley5652
557 posts
Aug 12, 2011
1:42 PM
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Yep,.as Greg says you can't open up a crystal,.once they are going they are gone ,.
Best Bet is look for another,.but also remember "You might find that drawing hard, or blowing hard - brings the problem on"
Even On a strong crystal you can damage em drawing hard, or blowing hard,.Bimorph Rochelle Salt crystal's do not like to be abused,..
My question is you say :
"Just for the hell of it, I hooked the MC-151 back up to a guitar cord with alligator clips jumpers;"testing,1,2,3," it worked! I cupped it and played some harp through it; it worked! Does anybody know what the hell is the problem? "
Did it cut in an out hooked to the alligator clips while ya played harp through it ?
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------------click Link Below -----------
Simply Unique Kustom Mic's By Rharley
Last Edited by on Aug 12, 2011 1:46 PM
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jbone
608 posts
Aug 13, 2011
4:30 AM
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i learned a long time ago how fragile a crystal is. i had one from 1955 and wanted a longer cable,so i took the old one off and soldered a new one on- without heat sinking! fried it on the spot.
i have been very lucky since then. i have a Ruskin with a good crystal in it which i've never had apart. i have dropped it a few times in 9 years but it still works great.
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http://www.reverbnation.com/jawboneandjolene
https://www.facebook.com/profile.php?id=100000386839482
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