Yamaha NS-690 Mid Repair

Sasquatch2

Active Member
I have a couple of 690 mids (JA 0701A) with the domes pushed in a bit. I have removed the screens and trying to seek the best way to restore the domes. Some have recommended vacuums, etc. I would like to try to disassemble them to see if I can reshape them from the inside after warming them up. A vacuum sounds a little harsh to me. Could someone explain how to get at the dome this way? Which screws (4 on the front/4 on the back) are to be removed so I can access this part of the driver? Any help you can offer is much appreciated. Thanks.
 
The tweeter may provide a clue here. IIRC, the four screws on the front secure the magnet to the the faceplate(?). The magnet can be removed giving access to the backside of the dome. I have not taken apart a Yamaha mid-range to confirm this.
 
Thanks SoCal Sam. I have only replaced a voice coil once on a Infinity tweeter and it was pretty easy. Remove the screws and the change the coil. Everything was designed to snap into place. No messing with the magnet. I wonder if the Yamaha mid is the same? I don't want to misalign anything and ruin any chance for success.
 
I have not taken apart a Yamaha mid-range to confirm this

I did many times ! the best way to act in my point of view is just take off the grill and use adhesive tape !
This is safe and easy ! it will not be necessary for you to adjust the mid because you don't touch the 4 screws ! :thmbsp:
 
Thank you clinic-audio...that is a great tip! No sense in making something more difficult than it is. I'll get back with the results.:thmbsp:
 
The tweeter magnet has tapped holes for the machine screws so there is no need to align the coil in the gap. Chances are this is the same for the mid-range. I wish I could give a definitely answer for the mid-range but I tossed my blown one a long time ago.
 
The tweeter magnet has tapped holes for the machine screws so there is no need to align the coil in the gap. Chances are this is the same for the mid-range.

True ! but there is a little gap and I remember to have used AG to be sure about perfect alignment of the coil .
 
Thank you.

clinic-audio, are you referring to an Audio Generator "AG"?

I do remember another thread where a member was attempting to repair an open VC on one of these puppies which included a photo. I'm wondering how he made out with the re-assembly. I'm going to search for that thread. Thanks again everyone.:thmbsp:
 
The tweeter magnet has tapped holes for the machine screws so there is no need to align the coil in the gap. Chances are this is the same for the mid-range.

True ! but there is a little gap and I remember to have used AG to be sure about perfect alignment of the coil .

I'm interested in knowledge, not who is right or wrong. Using your audio generator, what is the reference and how are you comparing actual to the reference?
 
Made some progress today. Didn't want to touch the 4 screws that hold the magnet on (front-per SoCal Sam) so I thought I'd try the back. Removed the 4 rear screws and removed the cup cover. Removed the insulation carefuly (very) and there it was, the back of the dome. I warmed it up a bit and pushed it back out carefully with my finger. There are still a couple of small minor imperfections so I'm going to give it some sunshine tomorrow to see if it might remember where it used to be. A hair dryer might be too severe. Not completely satisfied yet but tomorrow is another day. WooHoo!!
 
Hi Rob, I do remember in a previous Post of yours where you described using a brush and warm water (not sure about that part) to restore the shape of the dome....but I can't find the thread. I think you applied the warm water to the inside of the dome. Could you elaborate a bit? Thanks in advance.
 
No the warm water is applied to the outside, for the NS 690 mids what you did is the easiest way, The warm water may soften the domes enough to get the last wrinkles out by sort of 'ironing' them from the back with something firm but not hard.
 
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