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Post by bluesholyman on Jan 19, 2024 19:39:20 GMT -6
So the quick backstory is I bought this mic off of Reverb with the assurance it worked for a quite fair price. I think its early 70s but not sure. It arrived and I could not get a signal out of it. Discussed with the seller and he says crack it open and see if you can find a loose connection or anything a bump could have caused. 1st screw holding the cartridge assembly sheers off, the rest are frozen solid. He says I'll refund you the money, keep the paper weight. So I get to work with some WD-40 specialist and I am able to remove the rest of the screws after a day - that stuff is amazing. I still have one hole with a sheered off ridiculously tiny screw stuck in it. Figure out its a 4-40 screw, find the tap and #43 wire bit required, and after about 30 minutes of drilling and a careful re-tap, the hole is working again with a new screw ( lower picture.) Now onto figuring out what isn't working. No idea what could be wrong but it looks like the impedance selector may have been bypassed at one point, not sure - the wiring doesn't make sense to me how I see it. Next steps are to get the schematic and start testing stuff. My time is limited so this will go on for the next few weeks at least. A fun project if I can bring it back to life. Attachment Deleted |
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Post by stratboy on Jan 26, 2024 20:06:31 GMT -6
I’ll be watching your progress. I have a Shure 588 that I’ve been meaning to work on for years. Completely different mic but you’re inspiring me!
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Post by audiospecific on Feb 2, 2024 10:48:29 GMT -6
So the quick backstory is I bought this mic off of Reverb with the assurance it worked for a quite fair price. I think its early 70s but not sure. It arrived and I could not get a signal out of it. Discussed with the seller and he says crack it open and see if you can find a loose connection or anything a bump could have caused. 1st screw holding the cartridge assembly sheers off, the rest are frozen solid. He says I'll refund you the money, keep the paper weight. So I get to work with some WD-40 specialist and I am able to remove the rest of the screws after a day - that stuff is amazing. I still have one hole with a sheered off ridiculously tiny screw stuck in it. Figure out its a 4-40 screw, find the tap and #43 wire bit required, and after about 30 minutes of drilling and a careful re-tap, the hole is working again with a new screw ( lower picture.) Now onto figuring out what isn't working. No idea what could be wrong but it looks like the impedance selector may have been bypassed at one point, not sure - the wiring doesn't make sense to me how I see it. Next steps are to get the schematic and start testing stuff. My time is limited so this will go on for the next few weeks at least. A fun project if I can bring it back to life. View AttachmentView Attachment
It makes sense seeing a broadcast mic with the switch taken out of the circuit. This of course is a result of idiot DJs playing with the switch during their shift.
The only setting you want to use is the medium impedance, unless you are doing something weird like sending it to a guitar pedal.
But here is the tech paper on that mic that is probably next to impossible for anyone to find on the net. Also, be sure to remove any WD40 residue as it will promote oxidization. WD40 is a rust solvent that turns into a rust promoter over time.
The original capsule was a R56 Unisphere I (1950s) But the modern replacement would be R59
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Post by bluesholyman on Feb 2, 2024 11:26:06 GMT -6
It makes sense seeing a broadcast mic with the switch taken out of the circuit. This of course is a result of idiot DJs playing with the switch during their shift.
The only setting you want to use is the medium impedance, unless you are doing something weird like sending it to a guitar pedal.
But here is the tech paper on that mic that is probably next to impossible for anyone to find on the net. Also, be sure to remove any WD40 residue as it will promote oxidization. WD40 is a rust solvent that turns into a rust promoter over time.
Thank you for that, especially the diagram. I thought I had found this, but I don't ever recall seeing the wiring diagram in that level of detail - perhaps that is the "impossible to find" you are referring to. I was going to touch up the solder joints and hope for the best, but I think I am going to pull the impedence switch, or at least remove it from the circuit entirely. I suspect it is the piece causing me issues as the rest of it looks solid. Entirely possible the diaphragm got damaged in shipment, internally, but nothing obvious from visual inspection. |
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Post by audiospecific on Feb 2, 2024 11:52:30 GMT -6
It makes sense seeing a broadcast mic with the switch taken out of the circuit. This of course is a result of idiot DJs playing with the switch during their shift.
The only setting you want to use is the medium impedance, unless you are doing something weird like sending it to a guitar pedal.
But here is the tech paper on that mic that is probably next to impossible for anyone to find on the net. Also, be sure to remove any WD40 residue as it will promote oxidization. WD40 is a rust solvent that turns into a rust promoter over time.
Thank you for that, especially the diagram. I thought I had found this, but I don't ever recall seeing the wiring diagram in that level of detail - perhaps that is the "impossible to find" you are referring to. I was going to touch up the solder joints and hope for the best, but I think I am going to pull the impedence switch, or at least remove it from the circuit entirely. I suspect it is the piece causing me issues as the rest of it looks solid. Entirely possible the diaphragm got damaged in shipment, internally, but nothing obvious from visual inspection.
It could be the switch being bad. They had a tendency to nuke themselves when phantom was applied. But its not a total tragedy either if the capsule is bad. Its just a sm58
capsule screwed onto a bracket.
Yes, that was a scan from my service documents. So I doubt it is on the web.
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Post by bluesholyman on Feb 2, 2024 12:02:47 GMT -6
It could be the switch being bad. They had a tendency to nuke themselves when phantom was applied. But its not a total tragedy either if the capsule is bad. Its just a sm58 capsule screwed onto a bracket.
This is not an sm58 capsule, at least not one I've ever scene....the capsule is behind the blue silk and there is a large silver metal dome on the back side of it. This predates the current SH and Super 55 mics.  |
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Post by audiospecific on Feb 2, 2024 12:20:40 GMT -6
It could be the switch being bad. They had a tendency to nuke themselves when phantom was applied. But its not a total tragedy either if the capsule is bad. Its just a sm58 capsule screwed onto a bracket.
This is not an sm58 capsule, at least not one I've ever scene....the capsule is behind the blue silk and there is a large silver metal dome on the back side of it. This predates the current SH and Super 55 mics. View AttachmentLet me find the capsule data cross reference, since I know Shure Has that online.... Here it is:
That should be just a cast bracket with cloth glued over the openings.
The other ones in that era had an R50 capsule which is similar to a R96 but mounted by a rubber ring.
But thinking about them, I got this one an a EV mic mixed up which has the screw in type.
So its going to be like R96 or R132 depending on if its a smaller mount than the diameter of the diaphragm.
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Post by audiospecific on Feb 2, 2024 12:35:30 GMT -6
Btw, the release year for this mic was 1956.
R50 was a smaller diaphragm than the R56 and had the same diameter (cylinder shape) as the diaphragm. R56 was a big button with a smaller diameter mount on the backside. The SH and 55 have the same diameter mount as the diaphragm button.
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Post by bluesholyman on Feb 2, 2024 14:22:03 GMT -6
I peaked inside with a flashlight. This capsule is a solid metal dome, screwed down at top right and bottom left by some form of metal ring with tabs for the screws, which also appears to be glued to the outer right/left edges of the dome. I assume it comes out as one piece when the screws are removed.
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Post by audiospecific on Feb 2, 2024 18:51:01 GMT -6
I peaked inside with a flashlight. This capsule is a solid metal dome, screwed down at top right and bottom left by some form of metal ring with tabs for the screws, which also appears to be glued to the outer right/left edges of the dome. I assume it comes out as one piece when the screws are removed.
It should mount like a R96 does in a 526T
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