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aussievintage

Restoring the Rek-o-Kut

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Posted (edited)
54 minutes ago, aussievintage said:

 

I would prefer the max area of contact, so I would make sure the wood contacts all the ribs with some pressure if I could.

Yes, pressure and surface area. 

Hence my suggestion to drill holes small enough to screw down the topplate so the ribs are tight to the wood. 

On areas you can't drill through as it would be unsightly you can weld threaded inserts to the underside. 

Then use a threaded rod to secure the topplate to the plinth at the edges. 

 

Here are some pics to illustrate:

 

20181222_143209.jpg

20190130_172102.jpg

Edited by The Blues

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Posted (edited)
2 hours ago, aussievintage said:

Very tempted [Rek O Kut 120 Mono Broadcast Tonearm 12" on eBay], it's lovely, but it's only mono.  That means it actually isn't the right tonearm - my table is labelled "Stereo Table" in the centre of the platter.   Anyway I need stereo.

It could probably be converted from a mono arm to stereo.  However, I'd also be thinking that some latter 12" arms would probably be better quality (not implying that there are some vintage arms from that era that are probably very good quality, maybe Empire or Gray Research arms?). 

 

 

Edited by audiofeline

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10 hours ago, audiofeline said:

It could probably be converted from a mono arm to stereo.  However, I'd also be thinking that some latter 12" arms would probably be better quality (not implying that there are some vintage arms from that era that are probably very good quality, maybe Empire or Gray Research arms?). 

 

 

I'd absolutely love a Gray or one of those classic old shapes.   Alternatively, I am pondering making something very modern - maybe a long straight arm made from carbon fibre, maybe using a fishing rod blank or arrow shaft.  I don't think I'd go unipivot, but re-purpose a bearing from something else.  

 

 

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I have been attacking hum and rumble. 

 

Firstly, there was some small amount of hum which I tracked down to the ground of one channel being earthed to chassis.  This is how the arm was wired in the original table.  I remember noting it, then forgot about it :)   Probably the original idea was to not need a separate earth wire.  Of course, the separate wire works best.  One snip of the link, and the hum disappeared.

 

With all the cleaning and oiling and adjusting of the mechanics, the rumble is now very low now.  Well below surface noise.  I remember reading in a thread that someone could not get their B16 quiet enough for classical music.  I am lucky as mine is certainly up for it.  Enjoyed Carmina Burana and Rites of Spring so far this morning.  Wonder what the neighbours think.  Aah, they usually start lawnmowers etc on Sunday morning so, I think I am OK.

 

After a day of listening, and I know it's probably expectation bias, but I don't remember ever hearing bass with the slam and impact I am currently experiencing.  Kudos too, to the little Shure M91 cartridge (it's the little clip-in style).  With just a cheap aftermarket elliptical stylus, it is singing nicely.

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I went out fishing today, so not a lot happening with the ROK.     Over the last day or so, I have done two things that make it nicer to use.  The cork mat it comes with is thin, and rough, and very hard to pick up a record from.  So, I added a thin 12" cork mat on top.  This makes the edge of the record easier to grab.  I also raised the tone arm up the same amount to retain the VTA.

 

Also, it is VERY hard to cue and retrieve the tonearm as the fingerlift barely allows room to get a finger between it and the record, and also, you have to reach so much further with the 16" platter.  So I strapped a temporary fingerlift extension on with zip ties - and reset the VTF of course.

 

IMG_20200330_165256.jpg.9c0a3f6bd443f98e28c84424f9191df7.jpg

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I have decided this table is going to be one I use a lot of the time.  So, accordingly, not having a spare headshell yet, I have swapped cartridges in the existing headshell for something better.    My favourite cart is an AT VM95ML.    So, I put an older AT95 cart body on the headshell, and swapped the stylus from the VM95ML cart which is on the other table I used to call my 'main' table.   The VM95ML stylus will fit the older AT95 body and that makes it pretty much the same thing.

 

In the pic you can see the red 95ML stylus.  Also you can see the 12" cork mat just under the record itself.   Really good sound is now coming from this setup.  The nude microline stylus just extracts so much more detail from a  record. It separates out each instrument and sound.

 

IMG_20200331_110254.jpg.9abcebb7981f6af3d58e1a1bf7934926.jpg

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Cleaning and lubing the ROK is interesting.  I removed the idlers and found a very nice feature.  Their design for keeping the idlers oiled is superb.  The shaft the idler runs on is large and hollow, filled with felt, and has a hole in the side halfway down the bearing surface.  The top is a small cup, and obviously the intention is to fill it up with oil.

 

IMG_20200415_081557.jpg.65b4642814c605df8b5c44dc3388a08e.jpg

 

 

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I  have managed to replace the oil pipes/tubes for the motor.  I could not find anything that would connect securely to the oil points on the motor board so I arranged the tubes to sit nearby where it is easy to put oil in them.

 

The tubes are actually fuel lines from a hobby shop - must be used on remote control cars and things.  They fit tightly onto the flanged metal pipes coming out of the motor (second picture)

 

IMG_20200415_080936.jpg.bc70a161f4428cf2d9041ef76b43b712.jpg

 

IMG_20200415_080907.jpg.545ee89610b1a179641d9edb9ba7a244.jpg

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After a conversation about oils in another thread, I have been reading some other manuals for ROK G2 and T12 and some others https://www.vinylengine.com/ve_downloads/index.php?rek-o-kut/rek-o-kut_t-12_tr-12_t-43_g-2_en.pdf , looking for clues about what oil should really be used.  I will post here what I have found to keep it separate from the Commonwealth thread.

 

The tables in this manual seem to have a similar main bearing with the spiral oil groove and ball bearing underneath.  They recommend a "#9 S.A.E. Spindle Oil" .  So, as I sort of suspected, it needs to be a lighter oil than the SAE 20 that the Commonwealth idlers use.

 

The same oil is recommended for the wicked idler bearings.

 

They mention using "#20 S.A.E. motor oil" for the hysteresis motor in those models, which is different to the one in mine.  Still maybe the same should be used.  They described the bearing system as "oil-less bearings and saturated wicks", and say oiling is required every 1000 hours in "temperate climates"

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My efforts in cleaning adjusting and lubricating are paying off.

 

I am using a phone app that measure speed and wow & flutter.  Now I know the actual figure for wow & flutter is really just an estimate as wow & flutter specs are measured as frequency deviations of a tone playing on a record (3kHz I think).  However it does provide a good comparison to see if I am improving things, as it is very repeatable.   When I first measured this table after some minimal oiling, it measured about 0.2 %

 

Specs seem to just say it conforms to NARTB standards at the time.  I found a document from 1953 that says 0.2% peak (0.4% p-p).  However I was determined to do better.  I played around with the idler tension adjustment after reading that too much tension will increase noise.  I was getting consistent readings of about 0.15%.

 

Now, after removal and cleaning of both idlers and the main platter bearing, and lubing with some compressor oil I got locally at Tradetools, and also the fitting of oil tubes, ( into which I put some thin oil initially, and I think it needs the thicker compressor oil),   I now measure 0.07%.     I am trying to avoid pulling the motor apart, and that would help with rumble, not so much wow & flutter, I feel.

 

I am still cautious about adding MoS2 (molybond).  It might help, but it is black and would look terrible.  Maybe better to just service the table more regularly.  An old manual for a similar machine recommended oiling the motor every 1000 hours, so if I give the whole table a service every year, I think I will be fine.

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Sounds like it's coming along well. :thumb:

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9 hours ago, t_mike said:

Sounds like it's coming along well. :thumb:

 

It is.   In fact, I am currently using it as my main table.   If I get lucky and score a nice 12" arm, that will complete it nicely.   Well, plus I need to figure out what I want to to, plinth wise.

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While looking for a 12" arm, or coming up with a way to make one that I am happy with, I thought I should at least adjust the All Balance arm I am using.  Basically it needed a little height,  so I made a couple of shims (from balsa wood).  Running nicely level now.  Lucky because I can not get ANY more height due to the thickness of the baseplate and the length of the mounting thread on the arm.  Something to keep in mind when buying a new arm.

 

You may note that the cartridge looks a bit odd?  Well, it proves one thing - you CAN fit an AT VM95 stylus (an ML in this instance) to an old AT-95E cart, and it sounds excellent as well.

 

IMG_20200425_104342.jpg.f951a024566c758ce360d104003573cf.jpg

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After some weeks, I have noted that the speed is always just a tad fast.  33.4, 33.5, 33.6 even occasionally.  I have waited to see the variation because I know the mains can vary a bit.  The main reason I was monitoring it, is because I wanted to sandpaper the drive pulley to clean and smooth it out as much as possible to tweak that noise and rumble from the idler drive.

 

So I figured I had enough room to do it without the speed getting too slow.  So I carefully applied a strip of fine sandpaper evenly to the spinning pulley.  I did this in small stages, putting the platter back on and testing the speed each time.   I was monitoring the smoothness by pushing the idler against the pulley with my fingertip on the idler centre shaft.  You can really feel every bump this way.  

 

It is now running quite a bit smoother, and so I have put the platter back and I am playing some opera.  I am listening to the quiet passages and lead-in lead-out grooves, and first impression is that the residual rumble is now plain motor vibration, with little added noise - and it's a lot quieter as well.  Bonus is that the speed is fine tuned as well.

 

 

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There are many paths to motor noise reduction I have discovered.  I have been playing around, and haven't jumped into building a massive plinth for it yet.

 

My latest experiment dropped the rumble hugely.  I simply put a small piece of that Bunning's isolation rubber stuff under each corner of the turntable, between it and the old box plinth it was sitting on, and left the box plinth sitting flat on the shelf with nothing under it.  I am guessing that the heavy moulded and ribbed underside of the turntable is very stiff and massive enough already, and doesn't need to be bolted to a huge hunk of wood,  but it does need to be housed in a way that doesn't promote resonances.  So by isolating it with the rubber, and raising it up so there's a gap, the turntable is left free to control it's own vibrations, and this it does well.

 

Also, one other thing,  the rumble reduces even further as the motor warms up, so I guess the rubber is a bit hard on a cold morning, and the general heating to normal operating temperature helps soften it a bit.  This could be the motor mounts and/or the idlers.

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