This thread is for anyone with panels that lost output and shower cleaning didn't help. At this point you have nothing to lose, and new panels ain't cheap, so keep reading.
I should stipulate that my only experience with ML panels was a single Theater Center Channel panel restoration, and I'm not at all sure that my observations there would translate to a full-size panel-- but again, there's nothing to lose on a dead panel.
That restoration involved replacing the diaphragm but I now think it may be possible to disassemble a ML panel (separate stators) without destroying the diaphragm. If so; then merely re-coating the original diaphragm and replacing the charge ring would restore the panel to full volume and extend its life for many years.
The intimidating part of a panel restoration is replacing the diaphragm.... but if you don't have to, it's almost a piece of cake.
Observations from the Theater panel restoration, and why I think it may be possible to save the original diaphragm:
* There are a couple of reasons why I would not coat the entire diaphragm, within 1/8" of the spars. For the sake of brevity I won't go into that here but if anyone needs to know, ask and I will explain it in a separate post.
Enjoy the music!
References:
ML Theater panel rebuild link: https://jazzman-esl-page.blogspot.com/2011/11/compensating-diplole-phase-cancellation.html
Wire-panel assembly video (different type ESL but some aspects are relevant). Note in this video the charge ring is installed on the opposite stator, whereas ML installs the charge ring directly onto the diaphragm... either method works:
I should stipulate that my only experience with ML panels was a single Theater Center Channel panel restoration, and I'm not at all sure that my observations there would translate to a full-size panel-- but again, there's nothing to lose on a dead panel.
That restoration involved replacing the diaphragm but I now think it may be possible to disassemble a ML panel (separate stators) without destroying the diaphragm. If so; then merely re-coating the original diaphragm and replacing the charge ring would restore the panel to full volume and extend its life for many years.
The intimidating part of a panel restoration is replacing the diaphragm.... but if you don't have to, it's almost a piece of cake.
Observations from the Theater panel restoration, and why I think it may be possible to save the original diaphragm:
- I started the Theater panel rebuild assuming the diaphragm would be destroyed so I made no real attempt to save it.
- I first attempted to pry the stators apart, which only partially worked, as they were stubbornly bonded, and additional force risked bending a stator so I decided to cut through the remaining bond lines using a string saw (garotte) made from 60-pound braided fishing line. This worked quite well.
- The diaphragm remained intact where the string saw was used but lifted at the end where prying was used.
- I observed that by inserting the string between the diaphragm and [upper stator] spacer tape, the string rode atop the diaphragm, and cleanly parted the diaphragm from the spacer tape without destroying the diaphragm or the spacer tape.
- The string saw marred the adhesive coating on the periphery spacer tape but it was still partially tacky and otherwise intact so I applied a layer of 4-mil double-sided tape over it, to restore it's adhesion, and re-used it.
- After ripping off the old/damaged diaphragm from the rear stator, its underlying spacer tape was still pristine-tacky after 20 years, so I re-used it as-is.
- There's a good chance the original diaphragm could have been saved, had I used the string saw from the start.
- The original [stupid-expensive] periphery spacer tapes can be saved/reused.
- The original 4-mil double sided tape at the front spar-to-diaphragm bondlines must be replaced (it's cheap).
- The original foil charge ring must be replaced (also cheap).
- Separate the stators using string saw made from 60-pound fishing line, cutting lengthwise thru the bond lines as shown in the attached sketch.
- On front stator; leave spars in place but remove 4-mil tape residue from inner surfaces.
- Remove charge ring from the diaphragm; cleaning off the remnants by solvent wiping with acetone.
- Solvent wipe the entire diaphragm with acetone.
- * Mask areas on the diaphragm that will not be coated (see attached sketch).
- Spray-apply one coat of Licron Crystal ESD coating (see video link below). Remove masking tape and air dry for 8 hrs.
- Apply copper foil charge ring (see video link). Charge ring can be applied to the front or rear stator. If applied to rear stator, place adhesive side to diaphragm.
- On front stator; apply 4-mil tape to spars and over the periphery spacer tape. Leave backing in place for now.
- Temporarily clamp the stators together, connect power leads, and sound check with music to verify the diaphragm coating is conducting (Licron has never failed me but it's prudent to verify its conduction before permantly bonding the stators together).
- Upon passing sound check, remove backing from adhesive tapes, then mate and press stators together, using hand pressure along edges and over spars.
* There are a couple of reasons why I would not coat the entire diaphragm, within 1/8" of the spars. For the sake of brevity I won't go into that here but if anyone needs to know, ask and I will explain it in a separate post.
Enjoy the music!
References:
ML Theater panel rebuild link: https://jazzman-esl-page.blogspot.com/2011/11/compensating-diplole-phase-cancellation.html
Wire-panel assembly video (different type ESL but some aspects are relevant). Note in this video the charge ring is installed on the opposite stator, whereas ML installs the charge ring directly onto the diaphragm... either method works:
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