• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Dead Voice Coil Test - Voltmeter (Infinity/Braun Midrange)

Two Steps

Two Steps

Active Member
image.jpeg image.jpeg image.jpeg image.jpeg image.jpeg

Howdy Folks!

In another thread I bought some Infinity Monitor Jrs from a thrift store for $12. Yada yada yada...

Here is the dead Infinity Braun Dome Midrange.

No capicitance? From the terminals. When I put the MM to 200k and short the leads I get a 0 as I should.

There are no obvious signs of trauma to the wire so could it be just the super fragile speaker wire entry spots?

I DID TRY TOUCHING THE MM LEADS TO THE COPPER WIRE ITSELF AND I STILL GOT NO READING. Does this mean that there is a break somewhere in the coil and it's not passing whatever it's supposed to pass?

I guess this is my last effort before I ship it for repair or trash it...
 
Register to hide this ad
Most breaks on these Peerless(MB Quart) soft dome mids occurs on the front side where the tinsel wire disappears into the dome, within the hard coating and many times a clean break.
This can be fixed.
Other times a break can happen on the voice coil bobbin, hopefully where the wire ends its journey around the bobbin and to the terminal. This can also be fixed.
If the break occurs deep within the winding, bye bye.

EDIT: Set the meter to ohms or diode test for resistance.
IMG_0930.JPG
 
Last edited:
The voice coil wires coated with a laquer and will not give you a resistance reading since the wire is isolated. You need to go either to the terminal where the wire ends and is stripped of the laquer to make the contact or remove the laquer locally from the wire but it will either break the wire or you shorten out the coil.
If you don't get a reading at the terminal it will be hard to get ar reliable reading without putting the wire at risk.
 
As tubed said the break is most likely under the gummy coating were the wire pokes through and goes to the plastic frame. They can be repaired several ways. Clean off the gummy glue and try to resolder, run a new wire, or the most fun, pluck a fresh wire off the voice coil and thread it through. There's a great thread in the Infinity forum about repairing these. Here's one I repaired. Here's the thread I used to repair mine.http://audiokarma.org/forums/index....quantum-midrange-repair-with-pictures.398687/
image.jpg
 
Hmmm are those like 1.25" soft domes? If so, I will check my old shelf stock- I may have 1 or two I can give ya. I hate to see an old hurt speaker......
What ohm?
DC
 
dc270 said:
Hmmm are those like 1.25" soft domes? If so, I will check my old shelf stock- I may have 1 or two I can give ya. I hate to see an old hurt speaker......
What ohm?
DC
Click to expand...

That'd be awesome! Let me know if you have something in your 'junk' drawer!

The back of the magnet says 8 ohms and on other Infinity Braun repair threads, the guys who fix theirs say they get a reading of anywhere from 6.9 to 7.3. I don't know what that means however...
 
And the spec sheet says that they are actually 1.5" soft domes, not 1.25".

Someone else earlier referenced these mids being Peerless...they are actually Braun out of W. Germany. I read through a number of uber in depth threads using the search engine ma bob on the topic as I was picking these up!!
 
[/Quote]Someone else earlier referenced these mids being Peerless...they are actually Braun out of W. Germany. I read through a number of uber in depth threads using the search engine ma bob on the topic as I was picking these up!![/QUOTE]

They were, in fact, manufactured by MB Quart of West Germany, a then subsidiary of Peerless.
 
tubed said:
Someone else earlier referenced these mids being Peerless...they are actually Braun out of W. Germany. I read through a number of uber in depth threads using the search engine ma bob on the topic as I was picking these up!!

They were, in fact, manufactured by MB Quart of West Germany, a then subsidiary of Peerless.
Click to expand...

I was going to paste a thread discussing the topic at length but I see that you were a heavy contributor - so I wont for redundancy.

And I want to be clear, I am not being rude, accusatory, or trolling. I was just trying to convey to dc270 what I thought was what i needed. I know nothing regarding the issue and wasnt even born until 1985 :)

I was just going off of what I was trying to learn by scavenging the depths of AK!
 
^^^^^
Didn't think were being rude or trolling, TS:)
I was just pointing out a very common misconception about the origin of that driver.
Enjoy
 
Here is what I found and can offer you!. The other mid domes I have have round face plates! Both are 4.12 ohms, complete with screws
DC
 

Attachments

  • PICT0001.JPG
    PICT0001.JPG
    57.4 KB · Views: 10
  • PICT0002.JPG
    PICT0002.JPG
    69.5 KB · Views: 9
  • PICT0003.JPG
    PICT0003.JPG
    69.6 KB · Views: 9
  • PICT0004.JPG
    PICT0004.JPG
    63.3 KB · Views: 8
dc270 said:
Here is what I found and can offer you!. The other mid domes I have have round face plates! Both are 4.12 ohms, complete with screws
DC
Click to expand...

Hey DC! Thanks for your time and offer! I really appreciate it. You and several others are what make AK a great place (and resource).

I think I'm gonna pass however. I am going to try an actual Infinity one or get this repaired!

Again, thanks and you rock!
 
You must log in or register to reply here.
Back
Top Bottom