If you have bought the speaker second hand, or you are in the process of doing so(!), it is only prudent to inspect the outside first. Look for the obvious - scratches and dents on the front grilles. I have seen everything from pristine, better-than-showroom-perfect to serious cracks in the front grille. This damage is not to be taken lightly, check out the price of a new front grille in the Parts Section of this site, if you need motivating!
By the bye, there are only two “original” colours - black, and “bronze/gold”. The black finish is satin, not matt, on the grille and the wooden framework. White is produced in Germany, and is non-original, but very nice and every bit as good. Other colours? They've been re-sprayed by the owner(s) over the years. If someone has re-sprayed it, check that they didn't clog up the smaller grille openings with too much paint. Look at the back of the speaker. If it is in original condition (more or less) then you will see that the back of the speaker is covered in a diagonal pattern mesh that has a jute fibre mat glued to the inside of the mesh with bitumen - exactly that in the oldest speakers. It's black, it's icky, and it's there, if the speaker hasn't been fiddled with too much. Looking under the bottom of this stuff or around the side of it you may be able to see the dust covers with a torch and look for splits, cracks and such. Otherwise, you need its clothes off!
Look at the wooden side rails. The standard side rail is a light brown, clear finish in the shape of a thin, elongated banana, (what can I say?). It is held to the sides with three bronze coloured wood screws. The screws have a nicely recessed washer each. I have seen non-standard side rails fitted, and the screws used to affix them were too long, drilling into the sides of the bass panels - ouch! So, make sure you choose screws of the appropriate length and gauge before you split old wood with over-sized screws or screw into 6000 volts! I have found that suppliers of marine fittings usually have nice "antique look" brass and bronze screws that match nicely, fwiw.
Again, if these rails are knocked about, scratched and dented, then ask for a bit more off the price if you think its a bit high. You can, if skilled in woodworking, make or re-work the side rails. There are numerous examples of side rails on the web that raise the speaker from the floor, which is not such a bad thing from a mid-bass definition perspective.
- The wooden side rails are removed by removing the three screws holding them on. You will then see that the grilles are stapled to the sides with standard industrial wood staples.
- Remove the staples holding down the side of the grille carefully (its only aluminium) with pliers and a screwdriver.
- Place the speaker carefully on its back.
- Remove the line of 10 or 11 small (1/2 inch) wood screws that should be holding the bottom of the grille onto the frame. This completes removal of all standard, factory-fitted fasteners. Do a quick inspection for anything 'non-standard' before proceeding though.
- The grille is removed by very carefully lifting it out and upwards in a gentle arc from the bottom. The top of the grille is folded such that it engages a slot in the top, back of the frame. The grille must be removed so that this fold and overall curvature of the grille is not distorted to any extent. If you bend the grille badly, you'll never get it back together again properly.
Dust Covers and Panels...
You are now in a position, literally, to inspect the dust covers, and the treble panel in particular. You may not be able to visually inspect the bass panels at this point since the factory sprayed them with gray paint. Inspection of the dust covers should reveal quite a bit of dust(!), if the owner has never had the grilles off. This is easily removed with a gentle wipe with a cloth that has been soaked in detergent and water, and then wrung out to be mildly damp. We don't want a lot of water in the speaker whether it's on or off! Any splits and tears in the front dust covers will now be obvious, as will repairs to same. They are usually repaired with a little sticky cello tape, or similar thin tape. PVC tape is not suitable. If the dust covers feel brittle when you clean them, and there's a few repairs already, then you need to think seriously about replacing them altogether.
Here is the state of a typical, older dust cover (20 Y.O.) showing some dirt, and simple repairs.
The speaker shown above had a lot of black dirt accumulated around each bass panel rivet, and a clear film repair (bottom right) where the perforated bass stator shows through. It also had treble panel damage which is not clearly visible in this picture.
However, at this point look closely at the treble panel (in the centre). Look carefully into every perforation for carbon spotting. If you see any, then the panel has very likely been overdriven, and arced, causing burning and consequent carbon residue. Sometimes, these 'spots' can be as large as a twenty cent (Aus) piece, or about 25 to 30mm in diameter! In such a case, the treble panel may still even be functioning, if the burn out occurred far from the EHT pick up bolts, but it will not be functioning at optimum, as you can understand. It will, in this case, need repairing.
Now that you've given the front a good look over, go around the back of the speaker. The diamond mesh grille and accompanying 'rugs' of jute is held in place by about 18 to 20 small wood screws and some small washers. These are clearly visible around the periphery of the rear frame. Remove them with a flat blade screwdriver. The rear grille is easily maneuvered out, but watch those edges(!), they'll cut you like a knife. In my opinion this is one of the most dangerous parts of disassembling a Quad, never mind the high voltages. Be very careful that you don't puncture the rear dust covers while removing this grille.
Now you will be able to see something like this:
As you can see the treble panel has even more of that felt stuff attached to the rear of the dust cover frame. To inspect the treble panel from the rear you need to carefully remove the felt with pliers and screwdriver. You will then be able to see any arcing (carbon spots) that were not visible from the front. Big arc spots will be easily visible from both sides!
Inspect the rear of the dust covers of each bass panel for splits, old repairs, et cetera. You can also take a close look at the three terminals at the back of each bass panel. The state of the heat shrink tube there will tell you if anyone has previously worked on the speaker.
You've just undressed your first Quad Electrostatic. If you found no damage to the treble or bass panels, or the dust covers, then this is a big plus. We're not out of the woods yet, though. If the speaker still doesn't play very well, seems to lack sensitivity, or if it is very old (most of them) and the EHT block appears untouched, then you will have to re-furbish the EHT block.That's it there, on the right of the photo, sitting on top of the mains transformer cage.