One Thing Audio
Quad
Instructions, New dustcovers for ESL 63
WARNING: Electrostatic loudspeakers can remain charged up for anything up to two hours after being unplugged from the mains. If possible, leave them overnight to discharge. But if a 'quick' discharge is required, short the HT (any connection on the HT line central rear) down to speaker chasis (ie. metal frame or spring grille contacts, bottom of speaker). NEVER work on a speaker while it is plugged into an amplifier, even if the amplifier is assumed to be switched off. Basic electronic skills and technical competence are assumed for anyone reading these notes.
1) Before starting: two layers of what is sometimes called “duck tape” (black reinforced cotton adhesive tape) is used on the standard ESL – one layer around the top of the speaker, the other around the bottom – to hold the metal grilles tight to the frame and to dampen vibrations. If the old tape is carefully peeled off, it is usually possible to re-use it. Alternatively, a reel of the tape can be purchased from some hardware stores or component companies such as Farnell or RS Components.
2) To remove the ESL’s wooden top, press down and slide firmly to the RIGHT (viewing speaker from the front).
3) To detach the stocking, pull the top ‘wrap-over’ section off the Velcro. Roll the stocking down the speaker, low enough so that the bottom layer of duck tape is visible. Remove both the top and bottom layers of duck tape – roll the tape onto something (a can or bottle will do) if you wish to save it and re-use it.
4) Using a flat screwdriver, prise outwards the top corner of the grille from its ‘rail’. Insert forefingers behind the gap and slide downwards. This will release one side of the grille entirely out of its rail. Do the same for the rear grille (assuming you want to replace the rear dust cover as well). NOTE: “duck tape” is also used down each edge of the grille. If the glue has dried out, the tape will want to part from the grille. Allow it to do this, retrieve the tape and re-glue it onto the grille edges.
5) With the same flat screwdriver, ease out the top corners of the dust cover frame, then run a finger down the gaps, releasing the dust cover from its rails. (The centre part, top and bottom, will have to be ‘eased’ off the rails as the aluminium supporting rails get in the way). Slide out the dust cover frame, to the right or left.
6) Removing the old dust cover from the frame is an easy matter. Do NOT attempt to remove the original double-sided adhesive tape from the frame: this has remarkable adhesion and will not easily be removed. Instead, burn out the original dust cover with a soldering iron, moving the tip of the iron inside the frame, all the way round, making a ‘clean cut’ of the original damaged dust cover which you may dispose of.
7) This will leave you with the dust cover frame less the original dust cover material – but with the original adhesive fixing tape and remnants of the ‘old’ dust cover still affixed.
This will prevent the plastic frame from detaching itself from the chrome corner fixtures. Clean round the frame to remove crease or dust particles.
8) Using the double-sided tape provided in the kit, apply four new strips over the original tape, pressing hard down, but do not, for the moment – remove the tape’s protective backing layer. Put the frame to one side for the moment.
10) Carefully cut out a square of the new dust cover film,
but bigger than the dust cover frame (so that it overlaps the frame by several inches all the way round). Again, put this to one side for the moment – draping it over something smooth ensuring that it is not snagged or damaged.
11) VERY IMPORTANT: Place the plastic dust cover frame down on a flat surface, new adhesive tape uppermost. As some small movement is still possible from the corners of the frame, it is critical to ensure that the frame sits “square”. If the surface on which you have placed the frame is a perfect rectangle, use the sides as a template to align the frame. If not, find some method to align the frame to ensure
‘squareness’ – failure to do this will result in distortion of the film and frame beyond the heat gun’s ability to correct!
12) Carefully peel off the backing tape – then check again that the frame is lying “square”.
13) Two pairs of hands are needed for the next procedure.
Take up the over-sized square of film you previously put to one side. With 4 hands, hold the square of film over the frame (do not pull too hard otherwise the film will tear – and at this stage do not allow the film to touch the sticky surface of the tape). With 4 hands applying gentle pulling pressure on all four corners of the film to encourage it to lie
flat (no wrinkles or waves) lower the film down onto the frame’s sticky surface. Some small wrinkles may remain – but these shouldn’t matter: they will be taken out in the next process, when the heat gun is applied. [If you have made a mess of things, don’t worry: there is plenty of film supplied for you to have several goes, if necessary!]
14) Although the new film may appear a bit ‘floppy’, the frame is now ready to be clipped back onto the speaker rails.
Feed the frame in from the left or right, behind the central vertical supports. Begin the ‘clipping-on’ process by concentrating on one corner only - pressing the corner section of the dust cover frame onto a small section of the vertical and horizontal section of the rails: then move along in all directions until the entire frame is secured onto the rails.
15) HEAT GUN TREATMENT. If the heat gun has two settings, do not use the hottest setting – use the next setting down. Hold the gun’s nozzle about 10 inches (25 cms) away
from the dust cover surface, and move up and down, and from side to side. At first, concentrate on getting the overall tension correct – move the gun fast enough to see results (if you are moving too fast or the gun is too far away, the film won’t shrink)
Withdraw the gun as soon as you have achieved the desired tension – do NOT concentrate on small sections overlong, otherwise you will burn a hole in the film. The film is pretty resilient and will not burn easily (the correct tautness should be achievable long before the film melts!) But if the unthinkable should happen – you are now an expert and should be able to repeat the entire procedure with confidence!
NOTE: the 12mm double-sided tape supplied should complete up to 6 dust cover frames. If more tape is required (or larger roles) it is readily available from most components suppliers such as Farnell or RS Components.
Good luck! Your new dust covers should last many years, but it is a good idea gain access to the dust covers every 3 or 4 years for inspection and re-tensioning.
One Thing Audio,
November 2010.
