Older "Patent Pending" Shure 545 Unidyne III Mic - Low Output

[buck1110]

Hi,
I recently got an older Shure 545 Series 2 ("Pistol Grip") microphone.
This particular microphone has the "patent pending" working, both: on the chrome grill ring and stamped on the metal just below the joint of the lower base and the mic.
I've fixed the switch, but now I'm getting a low output signal, somewhat "thin" or "hi-pass" in nature. I'm wanting to check the wiring around the capsule and around the transformer; however, there are some obstacles...
The grill area with the chrome label ring that normally rotates freely (at least on "newer than patent-pending" Unidyne III models) does not rotate, and the black plastic section that meets the metal section (and normally unscrews) seems to be glued on.
Whether these parts were glued after a repair or from the factory is unknown to me.

In order to unscrew a glued on part, what would a recommendation be? I was thinking that using a light amount of heat to gently see if the glue might release, or maybe a small amount of alcohol to seep down into the threads..?
Additionally, viewed from the back side of the "wand" portion of the mic, the circular plate cover common to pistol grip mics is missing (you can see where it had been glued on, but now wires are exposed).
What is a little unusual is the light-colored wax-type material that covers up the transformer area down in the hole. I wonder if the substance could be melted away from the electronics, or if that would damage the transformer, etc?
Maybe because this was patent pending, they were trying to hide the electronics until the patent took effect, or maybe it was potted for acoustic reasons?
Also, how would I replace the wires that run down in the spring? I can't find a way to release the spring from the mounting areas.
How would I go about disassembling this without destroying the transformer and diaphragm sections so crucial to the sound?
Thanks!


View attachment IMG_0053.JPGView attachment IMG_0054.JPGView attachment IMG_0058.JPGView attachment IMG_0059.JPGView attachment IMG_0060.JPG

 

[Walrus]

Yes, Shure did used to glue the cartridge to the base, a strap wrench was the recommended way to undo it.
The grilles did sometimes get stuck and not rotate, or possibly someone has glued it back on.
Not sure about very early mics, but the later ones had silicon sealant in the base to hold the transformer and to provide the correct rear acoustic response.
The spring is attached to the connector element in the base, unscrew the tiny screw then pull out the connector and desolder it from Pin 1.
Re the low output, is the cable wired for High or Low impedance and what pre are you using.

 

[user 130681]

This microphone is low impedance and requires a balances XLR connection to a balanced microphone pre amp otherwise it will sound very tinny and lack bass response.
I have fitted Beta58 cartridges to these in the past with great success.

 

[Walrus]

The 545L lavalier mic 150 Ohms, and the 546 50/150 Ohms, were the only ones that were low impedance only, the rest were all dual low/high impedance.
But if the cable is wired for high and you plug it into a low impedance mic amp it will as Jon S says sound off.

 

[buck1110]

Thanks for your reply.
I've been testing the mic with its included cable (a 4-pin Amphenol to 1/4 inch plug) and running it into a small guitar amp. If I had an Amphenol connector, I could make a cable to take it to XLR and then test with a line transformer possibly.
That may be my next step.
Any ideas about where I might be able to find an Amphenol to XLR adapter for this type of mic?
Thanks again!

 

[Walrus]

Amphenol 4 pin connectors are as rare as hens teeth now.
The original cable was 3 core plus screen, white and black gave you balanced low impedance, and red with screen gave unbalanced high impedance. How is the jack wired?

 

[buck1110]

Thanks!
I had a look, and here is the wiring at the jack.
(as a side note, it looks like the wires that connect to the jack are 2 of each color on the same lug. e.g. 2 white, 2 red, 2 blue, 2 black. The 2nd of each goes to the switch. I'm not sure how this affects the impedance, if at all, as the switch seems to be meant to function as just a 'mute' switch. It looks as though this arrangement would cause the switch to not work, although it does. In other words, one red wire, for example goes to the switch and another goes from the same lug straight into the microphone.)

Here is the wiring pinout at the jack.
black (ground) - pin i.d. # 1
white -pin i.d. # 2
blue - pin i.d. #3
red - pin i.d. #4

On the switch (DPDT), the red and black wires arrive from ground (1) and red (4), and when the mic is unmuted, they connect to white (2) and blue (3) respectively. Or, to make it simpler:
black goes to white
red goes to blue
and then on into the mic itself.

When you mention "screen" is that the same as the ground shield?

Thanks again

 

[buck1110]

I've got the connection for the cable as well...
Pin 1 on the 4 pin amphenol (ground) to ground sleeve on the 1/4 plug.
Pin 2 on the 4 pin amphenol to tip on the 1/4 plug.

 

[Walrus]

The switch should short the two windings of the transformer to mute the mic.
I think what you describe is actually how it should be.
https://pubs.shure.com/view/guide/545-S/en-US.pdf?clean_category=User GuideSounds like the mic is wired for High impedance, so plugging into a guitar amp should give a good level of volume.
Taking in to account the fact that the grille doesn’t move, and that the sound is low level and thin, I would suspect the diaphragm s either damaged or its movement has been restricted by some foreign body.
I think you may need a new cartridge.

 

[raketenmann]

I've got the connection for the cable as well...
Pin 1 on the 4 pin amphenol (ground) to ground sleeve on the 1/4 plug.
Pin 2 on the 4 pin amphenol to tip on the 1/4 plug.

Hi
I repaired several 545‘s. Now I have one that misses a little bass that I can‘t figure out where the problem is, but that‘s another story.

On all the 545‘s I have here was always Pin1 ground Pin2 HiImpedanceHot Pin3 LowImpedanceHot Pin4 LowImpedanceCold. So you need to get Pin1 to XLR Pin1; Pin3 to XLR Pin2 and Pin4 to XLR Pin3. Don‘t mess with colors: the original shure manual is pretty comfusing as they refer to the colors inside the cable, but the cables inside the microphone have a different color code.

I think first you need to take off the grill and inspect the diaphragm. Then you can tell if theres something wrong. These capsules are very well built and don‘t break so fast. You need to peel off the sticker on the gril, there where is says Unidyne, underneath you‘ll find two holes. In one of the holes you‘ll see two pieces of Metal. You need to push these inside to releas a spring to take the grill off. You need to fotate the grill, you are not able to push in the spring in every position, there are four spots where this is possible, but you will feel it.

Check if the diaphragm is clean, no dirt, clean it. You can fill in some new windscreen foam in the grill when you‘re already at it.

Sometimes also faulty connections and switches can cause a lowend loss. Probably a soundfile would help!

 

[swpaskett]

Check ham radio sites for 4-pin Amphenols. They were very common on ham gear 40+ years ago and commercial 2-way for that matter. If you feel rich, look here: Microphone Connectors: Vintage Amphenol
For a small mortgage he will have some stashed in a rabbit hole somewhere.
Another source for old connectors is https://fairradio.com/. Cheaper but not as reliable as the other guy.

 

[CJ]

I do not have a ton of mic experience but most of the problems I see are open voice coils on the capsule, those thin wires vibrate with the sound. This is always hit and miss as far as resoldering goes. And who knows how long they last after a repair job. If one end is open you can still get a little sound out of the mic due to C leakage. See if you can measure dcr of capsule.

 

[raketenmann]

I do not have a ton of mic experience but most of the problems I see are open voice coils on the capsule, those thin wires vibrate with the sound. This is always hit and miss as far as resoldering goes. And who knows how long they last after a repair job. If one end is open you can still get a little sound out of the mic due to C leakage. See if you can measure dcr of capsule.

I don‘t think this is a problem the Threadopener has to deal with. If the voicecoil is disconnected, to problem would be no sound at all….

 

[buck1110]

Check ham radio sites for 4-pin Amphenols. They were very common on ham gear 40+ years ago and commercial 2-way for that matter. If you feel rich, look here: Microphone Connectors: Vintage Amphenol
For a small mortgage he will have some stashed in a rabbit hole somewhere.
Another source for old connectors is https://fairradio.com/. Cheaper but not as reliable as the other guy.

Thanks for the leads in this. Unless I find one of the rare L3MN Switchcraft adapters, I'll probably need to make a pigtail adapter cable. I think the hardest thing is finding someone to machine an adapter with threads, etc, which would be pricey.

 

[buck1110]

I do not have a ton of mic experience but most of the problems I see are open voice coils on the capsule, those thin wires vibrate with the sound. This is always hit and miss as far as resoldering goes. And who knows how long they last after a repair job. If one end is open you can still get a little sound out of the mic due to C leakage. See if you can measure dcr of capsule.

Thanks! My next move is to try to unscrew the top part to inspect the leads. I found a nice webpage that talks about using desoldering braid to solder those really small leads from the capsule. How to Fix a Broken Dynamic Microphone
Do you think that desoldering braid would work well?

 

[buck1110]

.......

I think first you need to take off the grill and inspect the diaphragm. Then you can tell if theres something wrong. These capsules are very well built and don‘t break so fast. You need to peel off the sticker on the gril, there where is says Unidyne, underneath you‘ll find two holes. In one of the holes you‘ll see two pieces of Metal. You need to push these inside to releas a spring to take the grill off. You need to fotate the grill, you are not able to push in the spring in every position, there are four spots where this is possible, but you will feel it.

Check if the diaphragm is clean, no dirt, clean it. You can fill in some new windscreen foam in the grill when you‘re already at it.

Sometimes also faulty connections and switches can cause a lowend loss. Probably a soundfile would help!

Thanks! I'm working on getting a soundfile next few days.

Regarding the spring clip by the grill. I've read that some people experience damage to the diaphragm when removing the spring? Is it good to use one of those snap ring pliers to grab the spring before it can get onto the diaphragm? (snap ring pliers at Harbor Freight Snap Ring Pliers with Interchangeable Heads) Or are the pliers more for re-attaching the spring when you're putting it back together?

Also, I read someone on a post talk about 'sucking' or lightly 'vacuuming' the grill end to pull any debris off the diaphragm (and sometimes to reverse any inverted diaphragms). If it wouldn't hurt the diaphragm, I might more likely use the vacuum, as this mic has been around the world. lol

Thanks for the tip about the windscreen foam. Is there any modern type of foam that is just as pliable, but may last longer?

 

[buck1110]

The switch should short the two windings of the transformer to mute the mic.
I think what you describe is actually how it should be.
https://pubs.shure.com/view/guide/545-S/en-US.pdf?clean_category=User GuideSounds like the mic is wired for High impedance, so plugging into a guitar amp should give a good level of volume.
Taking in to account the fact that the grille doesn’t move, and that the sound is low level and thin, I would suspect the diaphragm s either damaged or its movement has been restricted by some foreign body.
I think you may need a new cartridge.

Thanks very much! After a good study, I've come to appreciate the design of the wiring of this mic!
Is there a good diagram and explanation about the diaphragm, its attachment to the capsule, what it's made of, and what causes it to be fragile (thin-ness?)
Also, I've read that sometimes a diaphragm gets out of alignment and, while it can be recentered, it may be arduous. However, one guy I found in a Google search mentioned that he uses a signal generator to play a sine wave into the mic, turning the diaphragm of the microphone into a speaker, so that you hear a slight buzz. He said that you can tell when the diaphragm is, in alignment, when the buzz hits a sweet spot.
The frustrating thing is that there's just a little info here and there about this kind of stuff. Does anybody know more about this kind of thing? Thanks!

 

[Walrus]

Years agoI used to work for Shure UK servicing mics etc. but we didn't do anything more than replace the cartridge, so I never tried to do anything with the actual diaphragm.
Generally speaking, it never came loose unless something drastic had happened.

I did come across a number of failures where people had continually twiddled with the grille, and in doing so had worn away the outer area of plastic diaphragm
so much that the inner bit with coil attached was loose. This gave the same efeect as you describe.

The usual way to remove the grille, is to rotate it until the Cardiod symbol is positioned above one of the cutouts in the catridge body (but one that has the
yellow tape in, as that is where the fine wires run down from the diapragm!).
You then poke around by the symbol with a small jewellers srcewdriver until you locate the hole, which enables you to push the lugs of the locating spring inwards
letting you carefully! bend off the grille.
Hopefully the picture will explain.

However, if your grille has been glued on, then unless you are fortunate that the cardiod symbol is already over one of the cutouts, I think you
may damage the diaphragm trying to remove the grille.

 

[raketenmann]

When your grille is glued, it could get hard to remove. Try with isopropanol, no Aceton cause aceton destroys the laquer on the wires from the voice coil. If you can‘t remove it: try to destroy the grille with a saw in order to release it. I mean - what could you loose? If the mic doesn‘t sojnd right it is broken anyway.

The 545 on my bench had this problem: the diaphragm camo loose after removing the grille. I don‘t know if it was loose before or not, but it was of like 3/4 of the edges. But that 1/4 attached was enough to keep it perfectly aligned. Only thing i neede to fill slme tiny bit of glue around the edge to put it back. Did the same on a Beyer M67 with success. But still: slme loss of the lowend is still there, a tiny bit, but I don‘t know how to solve..

And yes: i use sinewaves often to check a diaphgragm. Try different testtones. If it distorts, it touches the motor slmewhere… but you can‘t realigne It that way because you would need to glue EDIT: I mean wou would need to remove the diaphragm (probably with a sharp knife or something) and then glue it back, Also: most of the times a diaphragm is not aligned perfectly, it is not off center, more common is the problem, that the diaphragm is not flat to the motor or too close to the motor and can't move deeply....

 

[buck1110]

And yes: i use sinewaves often to check a diaphgragm. Try different testtones. If it distorts, it touches the motor slmewhere… but you can‘t realigne It that way because you would need to glue EDIT: I mean wou would need to remove the diaphragm (probably with a sharp knife or something) and then glue it back, Also: most of the times a diaphragm is not aligned perfectly, it is not off center, more common is the problem, that the diaphragm is not flat to the motor or too close to the motor and can't move deeply....

Thanks for describing your technique! I was wondering what the "motor" is? is it the term for what is under the diaphragm? Many thanks.