One of our SM57's is messing up.

I opened it up (unscrewed the halfs) and wiggleda couple wires. The yellow wire cam loose easily. Easy fix, I thought. So I soldered it back to the post on the capsule.

I plugged it in to check it and it sounds 'tubular'. Very middle range tube sound.
It is also measuring a bit weaker than other dynamic mics I have here to compare with. Unfortunately I didn't bring another home 57 to compare directly.
Should there be continuity from each post on the transducer (capsule) to each of the three prongs of XLR?
Nothing is grounding to the case. I checked that with continuity test.
Green wire looks like it may have been 'crimped' as I observe a flat spot in it. If shortened to eliminate the flat spot it will be too short to solder. It appears all three wires go thru the foam down to the XLR connection, is this correct?

It is weird in that it 'works' but does not sound correct.

Any ideas?

FWIW the top half of the recorded signal will clip before the bottom half when displayed as a wavform..
seems like a phase issue, but I didn't change any wire connections (only resoldered one wire).

Check that pinched green wire, it likely is now open.

Use your ohmmeter to check the continuity of each wire from capsule connection to pin connection, one at a time.

Be careful trying to measure continuity of the capsule, use one of the higher ohms settings to reduce current applied to the voice coil. Using the low ohms or Diode scale setting can sometimes pop the voice coil of the capsule...

--Mac

So there should be continuity from the capsule to the XLR? Thanks, should make it pretty straight forward.

Using RX1K on a small AA battery powered unit, good enough? Thanks

I almost got so SM 57s cheap once from a guy who said that sounded bad. I checked them out and indeed they did however before i plugged them in in front of him I knew they would. They had wrapped colored tape around the mics up near the head for ID. Well the SM 57 has a little hole up there that vents the back side of the diaphragm. If you block that it can't move properly. I didn't have the heart to cheat the guy. I removed the tape and they were perfect.

Funny, this one has tape up near there for ID also, but not on the vent. That vent ring is missing and the tape is farther down by just a little. I do remember that part of the other SM57's, a small screen like band that this one is missing.

On further testing, I removed the XLR connector and see that I have back-yellow-green at the capsule end, and black-red-blue at the other end, so there is a connection in between. Also, continuity at RX1k is not responding at all from one end to the other on the red/blue and the yellow/green wires using any combination. The black one seems just fine.

So I'm thinking Barry somehow blew something in the larger half, where the colors change. Must be a reason for that change, not just a continuous wire. Maybe I'll finish taking it apart just to see what's involved between the cartridge and the XLR connector.. looks like an intriguing assembly inside that cone.

There is an audio transformer between capsule and mic then. DC continuity won't cut it as DC does not flow thru a transformer.

By 'capsule and mic' I assume to mean capsule and XLR (?).

Gonna make it more difficult to test I guess with what I have on hand. I was hoping somebody on here had yanked a couple SM57's apart before. May be easier to just run to the store and see what mom/dad want for one.
..and finish ripping this one apart to learn from.

Shure publishes online user guides. Schematic is at the end of the .pdf

http://www.shure.com/stellent/groups/pub...pro_sm57_ug.pdf


--Mac

Thanks

Thanks for that link Mac. I'm not having trouble with my 57's right now but I did not have that doc. Tucked it away in my manuals folder in case of future need.