Listening #121

By the end of last month's column I'd invested a total of $290 in acquiring and refurbishing a 55-year-old Rek-O-Kut Rondine Jr. turntable. In the weeks that followed I spent just a few dollars more on some small parts—one of which sprang from a technology that I don't believe existed in the 1950s—that made small but welcome improvements in the performance of this outwardly simple player. I'll come back to those improvements in a moment, but for now let's get started on putting Junior back together again.

As you know from the last installment, it was surprisingly easy to find replacements for the Rondine's rubber isolation grommets, which had cracked and crumbled with age; would that it were so easy to install the new ones. As anyone who's ever tried squeezing a stiff grommet into an opening of finite size can tell you, this took a certain amount of effort—so much that I began to wonder if I'd ordered the right size after all. But in time—with a bit of coaxing from a small, flat-bladed screwdriver wrapped with a piece of fabric to help prevent the rubber from tearing—all seven snapped into place. The new grommets didn't come with new brass ferrules, so I cleaned and refitted the originals, the latter task made less daunting with a very small amount of light oil. Bear in mind that the ferrules must be fitted only from the side of the grommet where the molded center tube is the longest; those tubes face downward on the main top plate, while the grommets fitted to the motor plate are installed with their center tubes facing upward.

After replacing the top plate's trio of isolation grommets and brass ferrules, I reattached the idler-wheel support mechanism at those three points using ¾" flat-head bolts, secured from underneath with very light nuts. (Washers aren't used against the flared ends of those brass ferrules—or at least they weren't on either of the Jrs. at my disposal.) To avoid getting oil or sawdust on the newly resurfaced idler wheels, I decided to wait until all else was done before installing them. Also, before reattaching the motor, I attended to some chips in the finish of the edge of the top plate: Volkswagen Silver Leaf Metallic touch-up paint, purchased from a local dealer, proved an acceptably good match. I also touched up the area corresponding with the Rek-O-Kut's control knob, but that turned out to be a waste of time: after reassembly, the new paint was worn away in a matter of minutes. Live and learn.

I cleaned the Rek-O-Kut's motor casing before reattaching its spade-shaped isolation plate—now fitted with four new grommets and ferrules—then cleaned the upper and lower lubrication tubes using a pipe cleaner dipped in lighter fluid, most of which I blotted away with a tissue after applying. I also cleaned the motor pulley, but neglected to check its fit on the armature—and that turned out to be a mistake. If you set about rebuilding a Rondine Jr. or similar Rek-O-Kut, take my advice and use a suitable wooden drift to seat the pulley all the way onto the shaft, as far as it can go; failure to do so will result in occasional light rubbing between the 33 1/3rpm idler wheel and the 45rpm portion of the pulley—interference that, in my case, proved distinctly audible.

I fitted the motor and its isolation plate back together, carefully aligning the four remaining ¾" flat-head screws with threaded holes on the motor's own top plate. (I saved the oiling of the motor for later, since the lubrication tubes seem prone to drip if the motor assembly is tilted too far in their direction, thus posing a serious risk to the unfinished wooden plinth.) The finished motor assembly had to be rebolted to the top plate at two points—a small hex nut near the platter bearing and the threaded control knob at the front—but before doing so, I replaced the two 8-32 machine bolts that secure the metal stops used to limit the control knob's travel: Because the original slot-head screws were pitted and corroded from carelessly made adjustments, I substituted nice-looking Phillips-head bolts of stainless steel.

Because I'd discarded the badly worn original AC cord during disassembly, I now needed to remake some of the Rondine Jr.'s electrical connections. Simple enough: Of the two wires that exit the motor casing, one goes straight to one leg of the AC cord, the other to one of the two terminals on the SPST (Single Pole Single Throw) power switch; the remaining switch terminal goes to the remaining leg of the AC cable—and that's it. There should also be a capacitor across the terminals of the switch, to suppress noise and prevent switch bounce, and a thin, braided ground wire between the motor and a washer on the rearmost of two bolts that fasten the motor isolation plate to the main top plate; both had broken on my sample, so both got soldered back into place. (The Rek-O-Kut, like most such turntables, uses a shaded-pole induction motor, so a "phasing capacitor" isn't required to get the motor spinning in the correct direction.) A final note on turntable cosmetics: Although it's not something I've seen on any other Rondine Jr.—I don't know about other Rek-O-Kut models—I asked my friend Neal Newman to polish the rim of my platter, which he did. Superbly.

Hidebound
I returned my attention to the plinth project, for which I'd sawn a total of eight sheets of ¾" plywood, each measuring 13¾" by 22¼". In last month's column I described the size and shape of the cutout required to accommodate all of the Jr.'s underdeck parts, and that's the opening I made in the two top layers of my plinth. I temporarily fastened the rebuilt Rondine Jr. to layer 2 and, working from beneath with a straightedge, marked off those portions of the opening that wouldn't be needed for clearance in layers 3 and 4. The result was a roughly kite-shaped opening that provided sufficient room for motor, platter bearing, and wiring. Layers 5 and 6 required only a smaller, squarish cutout, to accommodate the bottom of the motor. And because I'd learned from the mistakes I made while building a plinth for my Garrard 301—I was late in realizing that a compliantly suspended motor may sit lower than expected, once the relevant springs and grommets have settled in—I applied the same cut to layer 7, just in case.

I applied one more lesson learned from that 301 project: A few months ago, I noticed that the left-rear corner of my Garrard's cast-alloy chassis became warm to the touch after playing just a few sides. Two things occurred to me, more or less simultaneously: 1) the heat was coming from the vicinity of the 301's motor, and 2) I'd neglected to ventilate the solid bottom layer of the plinth. As it turned out, at about the same time, an e-mail glitch prevented me from seeing a message sent by reader and speaker designer G.R. Koonce, who had given me that 301 in the first place: Art, your motor is probably overheating because you neglected to ventilate the solid bottom layer of your 301's plinth. Thus the bottom layers of all my plinths are now perforated. I haven't cooked a single motor since.

Gluing up was straightforward, despite my efforts to make things more difficult than they needed to be. As described in my March 2011 column on plinths, I prefer natural hide glue over modern aliphatic and polyvinyl glues; the latter remain a bit rubbery after drying, but hide glue forms a harder, altogether more wood-like join that enhances rather than impedes the transmission of energy. My hide glue of choice has been Franklin International's Titebond Liquid Hide Glue, which is premixed, doesn't require heating, and dries slower than raw hide glue, allowing for much longer setup times. (Scott Bowen of Franklin International assures me that Titebond Liquid, though sometimes hard to find, remains in production, and is stocked by most specialty woodworking shops and websites.) Earlier this year, when I set about repairing a minor crack in a Martin guitar, luthier Jim Merrill reminded me that Knox gelatin is identical to hide glue, and can be used as such when dissolved in the proper amount of water and heated in a microwave. I used that approach for gluing up layers 7 and 8, but reverted to Titebond for all others: the initial tack of the former is simply too strong for an application in which large parts must be aligned with care. As always, regardless of adhesive choice, the same old motto applies: One can never be too rich or too thin, or own too many generously sized bar clamps.

Love is in the air
Using a block of scrap wood to suspend the nearly finished motor unit over its opening in the finished plinth, I put a few drops of 3-in-One brand SAE-20 motor oil in each of the lubrication spouts, then lowered the Rek-O-Kut into place and secured it with six 6" by ½" stainless-steel wood screws. Then I installed the resurfaced idler wheels on their bearing studs, reusing the original thick and thin fiber washers above and below and adding two drops of light oil to the hub of each before securing them with E-clips. Finally, I replaced the steel bearing ball in the platter bearing well, added just enough Quaker State 10W-40 motor oil to cover it (this amount per the original Rondine Jr. instruction manual, available courtesy VinylEngine.com), and lowered the platter into place. Then I lowered into place the bearing shaft and platter, plugged in the AC cord, and applied power to the 33 1/3rpm idler.

For the first four minutes, the motor turned the platter only very slowly. During minutes 5 through 14, it perked up a little. Then, at minute 15—almost on the dot—Jr. got the lead out and hit full speed. Assuming the motor bushings are backed with some sort of oil wicks, and assuming the latter have become a bit gummy over the years, I'll hold off adding more oil until I've had a chance to disassemble the motor and give it a good cleaning.

Source : stereophile[dot]com