Sunday, June 24, 2012

Rek O Kut Tips



....vintage studio equipment in a scene from "The courtship of Eddie's Father", starring Glenn Ford..

Not much information can be found in cyberspace about the original Rek-O-Kut company based in NYC. But the company was a highly regarded manufacturer of turntables, tonearms and cutting lathes during the golden age of Hi-Fi. A lot of these idler driven turntables found duty in radio stations due to their quick start up time, stable speed and simple yet well executed engineering. My 1961 Lafayette catalog lists several idler models starting with the entry level 2-speed 4 pole induction motor driven Rondine Jr. L-34 [33 and 45] and L-37 [33 and 78], 3 speed Rondine B12 with same 4 pole motor as the L-34/L37, Rondine Deluxe B12GH which uses the Papst "flywheel" hysteresis motor and the the top of the line B12H which uses the HUGE hysteresis motor [see picture below]. By 1963 the L-34/37 Rondine Jr. series was replaced by the N33/34H belt drive which usually was fitted with the Papst motor. I have no experience with these models or motor but they have a good following.

All the Rek-O-Kut turntables are a model of engineering simplicity [no pitch control or eddy current brake] making the Garrard 301/401 and Thorens TD124 look over engineered. The motor and idler wheel arm assembly are individually isolated through rubber grommet mounts to prevent extraneous vibration from reaching the platter. The control switch physically moves the isolated motor with stepped capstan to engage the idler wheel at a chosen speed. Surprisingly the budget Rondine Jr. model employs dual idler wheels, the compromise being a simpler idler wheel arm assembly that does not need to be moved up or down to engage the capstan. Building a massive plinth for this model is very easy since it only requires a rectangular cut out to accomodate the motor unit. Due to the simple design the condition of the idler wheel[s] and rubber isolators as well as the few lubrication points have to be addressed to insure optimum operation.




The spindle is approximately 15.5mm in diameter and comparable to those found in a TD124 or 301/401. The platter is a precision lathe turned aluminum weighing about 5-6 lbs. depending on the vintage [earlier models were lighter].
Pull out the platter and then remove [3 screws] the bearing well from the motor board. The inner rim of the platter and spindle should be cleaned and the bearing well should be flushed with lighter fluid or denatured alcohol. There should be a small ball bearing inside the bearing well. Inspect the condition of the ball bearing and if it shows signs of corrosion, replace it with a 1/4" or 5/16" ball bearing available from a bicycle shop. A brand new shiny ball bearing insures a smooth and silent turning platter. I am not sure what the original diameter of the ball bearing was but find that a 1/4" seems to turn a bit quieter than the 5/16" and the platter rests quite low on the top chassis which looks just like in the original brochures.


The motor assembly can be removed from the top chassis by unscrewing the switch knob [1] and the 3/8" hex nut on the opposite side [2]. Now is the time to check the condition of the rubber mounts [1& 2 below and two more on the other side not visible] 4 of these are used to isolate the motor. If they are pliable and free from cracks just clean up all the grease and accumulated gunk. Replacement rubber grommet mounts are still available from Lord Corporation in Erie, PA although I have yet to encounter cracked or glazed rubber mounts.


Spray compressed air and WD-40 or better yet an all purpose degreaser from an auto supply into the oiling turrets [marked with arrows] while the motor is on. Once the bearings are turning without resistance, light oil can be added. As far as I can tell the motor is sealed and if the motor is still turning slowly, spray liberal amounts of WD-40 or degreaser into the motor shaft area particularly on the top and bottom bearings. After years of storage these areas may have gummed up. This was the only way I could get an L-37 motor to spin at the proper speed.



To clean the idler wheel bearing remove the E-clip and flush the stud [1], brass bearing [2] and washers with lighter fluid. For reassembly the sequence [from bottom to top] is - thick washer, thin washer, idler wheel, thin washer, thick washer then E-clip. I use thin gun oil to lubricate the stud and brass bearing.


Worn out idler wheel - the rubber is glazed and hardened, it also measures 1/32" less than 2.5"

Idler wheel condition is very critical for a quiet running ROK. Minute flat spot[s] in the idler wheel will definitely be heard as loud rumble. It has been suggested in the Vinyl Asylum that cleaning the rubber with lacquer thinner can rejuvenate a "not so tired" idler. With the platter off, turn on the motor and engage the idler while brushing the rubber wheel with a small paint brush dipped in lacquer thinner. Sometimes this trick will work but if the rubber hardens and becomes noisy when it dries up, it needs to be refurbished. It didn't work on this particular idler wheel set. So I sent them to Ed Crockett for a rebuild and he did a great job!


Refurbished idler wheel is exactly 2.5" in diameter

The turntable is now almost as quiet as my Garrard 301. Mechanical noise should not be audible 6 feet away in any idler driven decks. Another way to determine a worn out or glazed idler wheel is to try grabbing the platter and if it stops easily or does not offer much resistance the rubber is slipping.


According to the manual SAE 20 motor oil is the recommended viscosity for the main bearing. I use 5W-30 and you only need to pour in enough oil to cover the top of the ball bearing and then rubbing some to the spindle before inserting the platter into the bearing well. As pictured the tip of the 1/4" bearing I used is not quite submerged in oil and needs a couple more drops.


This picture shows the position of the set screws with rebuilt idlers installed and speed calibrated. Although there is no pitch control in most ROK models, speed can be fine tuned by moving the set screw along the arrow marked directions. The motor should have been running for at least 15 minutes before adjustments are made. In general it would be prudent to keep the idler to rim tension at a minimum [closer to the knob] to prevent premature idler wear. Too much tension with good idlers slow down the speed and generate more noise. Proper tension is obtained when the platter locks in to speed within a couple of minutes. I use a neon pilot lamp from Radio Shack soldered/heatshrink wrapped to a long AC cord to view the stroboscope markings.


Other Models


Rondine Jr. L-37 and LP743 - 3 speed

These are very similar in design but the earlier LP743 has rather innovative features - the same idler is used for 33 and 45 and the mechanical switch to the extreme right changes the height of the idler to match the 33 or 45 rpm capstans of the motor. The idler on the left is exclusively a driving wheel to spin [no contact with the motor capstan] the platter at 78 rpm. However the idler arm on the LP 473 is directly attached to the top plate so the idler is rigidly in contact with the inner rim on start up whereas the L-34/37's idler arm is mounted on a substructure isolated by 3 rubber grommets contributing to less mechanical noise but a tad less kick on start up.



The bottom idler wheel [marked with an arrow] is driven by the bottom capstan [78 rpm] in the motor shaft which then transfers the motion to the top idler wheel to turn the platter. This pair of idler wheels for 78 rpm are mounted using set screws instead of an E-clip. The platter on the LP743 is slightly smaller and a bit lighter but the main bearing dimension and quality are identical. Earlier versions of the Rondine Jr. L-34 or L-37 also used this square type motor.

Idler wheels are not interchangable between the B12H, LP473 and L-34/37.


Rondine Deluxe B12H fitted with a ROK S220 Gyropoise tonearm. This is the top of the line 3 speed model using a single idler wheel. Notice the tool kit under the platter?


The tools are provided to fine tune the speed and idler tension - the Allen wrench is used to remove the big control knob and the hex wrench to loosen the hex nut to fine tune the speed. As you slide towards 2 there is greater tension. Apply the same adjustment procedure as noted in the Rondine Jr.


Top motor is the hysteresis unit found in top of the line ROK machines, the bottom motor is from an L-37.


B12H stock plinth
Rek-O-Kut Rondine deluxe B12H after restoration and idler wheel rebuild.


For more information and discussion of Rek-O-Kut turntables visit the Vinyl Asylum Archives.

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