RekOKut Imperial II restoration project

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grooveguy
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Re: RekOKut Imperial II restoration project

Post: # 45066Unread post grooveguy
Mon Dec 05, 2016 11:41 am

Thanks for that, Jesus,

No, not powder-coated, simply sprayed. The texturing we specify for front panels is nominally "light," but I asked the painter to hit these pieces a bit harder. What they do is spray a very even coat over the panels and parts like this, and then open up the paint orifice on their spray gun and cut back on the compressed air. The effect is that the gun then sprays droplets of whatever size they have it set for, which give a pebbled appearance to the earlier smooth coat, which is given time to set-up a bit. The finer droplets give a finish on panels that can be silkscreened with the panel legend, but parts like these castings can afford bigger 'splotches' that hide imperfections in the casting surface.

Here, for example, is one of our front panels. The oblique lighting shows the texture, most visible near the square fuseholder:
718_front.jpg
Used to be that the paint was a mil-spec grade enamel that utilized some sort of nasty solvent. That type of industrial paint was outlawed in California, so what's used now is actually a water-based paint. It's still very rugged, and gets baked in an oven for some time, a lot longer than the enamel used to be. Once hardened, it's impervious to solvents and adheres quite well.
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Emilien03
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Re: RekOKut Imperial II restoration project

Post: # 47802Unread post Emilien03
Mon Sep 11, 2017 11:12 am

Hi, groveguy
Do you remember what capacitance values/voltage rating the "can style" capacitor with 4 sections are?
I'm restoring the power section on a R8B, the amp needs new filters but the capacitor has no markings in it.
thanks!
-Emilio

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grooveguy
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Re: RekOKut Imperial II restoration project

Post: # 47803Unread post grooveguy
Mon Sep 11, 2017 11:30 am

Gosh, Emilien,

I'm afraid not. Actually, I never owned or used the Rek-O-Kut amplifier, but initially rolled my own from a Seeburg jukebox amplifier, must have been back in 1958 or so. As soon as I became acquainted with solid state electronics in the mid-1960s, I never touched another tube. Not that I'm playing "elitist" or anything, but as my boss at the time said, "Jim, in the time it takes you to wire-up the filaments, you could build the whole thing with transistors."

I do remember those 3- and 4-section cans from childhood radio-restoration days. Generally somewhere between 20uF and 50uF per section and 450 VDC. Sometimes there was a lower-voltage section for bypassing output tube cathodes, maybe 50uF at 50V. Should not be critical, and the documentation for the ROK amp ought to be obtainable, here on this site or on the Web.

Somewhere recently I did run across an ad from a guy who 'builds' those multi-section cans from conventional axial-lead electrolytics. In that case I suppose you specify what you want inside and he tears apart an old can and puts new caps inside. With the way 'lytics have shrunk over the years, that sounds like a good plan to me, giving you a better part than the original. As for values, I don't think you can go too big.

Best of luck, and be sure to keep us informed of any and all progress.

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jesusfwrl
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Re: RekOKut Imperial II restoration project

Post: # 49137Unread post jesusfwrl
Sat Jan 27, 2018 4:16 pm

Last year was super busy, and although I had almost completed the restoration work, I never found the time to properly try it out. So while wondering what to do for New Years Eve/Day/etc, the idea was too good to pass: I pulled out a Casio toy keyboard and we decided to have a direct-to-disk recording session with it to try out the Rek-O-Kut and have some fun!

The Casio was hooked up to the R8-B hybrid vacuum-tube/germanium transistor amplifier and sounded great through a loudspeaker! I then added some reverb through a home-made spring reverb unit I built many years ago and mixed it in via the R8-B.

So we did a bit of cutting with the Audax head:
The machine works like a dream, both mechanically and electrically, after the restoration work. The first time I lowered the head, I was a bit conservative with the depth setting, and it seemed bit shallow. I had a look under the microscope (on the AM44 lathe, the Rek-O-Kut did not come with one) and was amazed to see that this little thing can cut a PERFECT 30 um wide (15um deep) groove all the way around a not particularly flat blank, with no advance ball or dashpot or any other form of advanced technology! No vertical instability, no lifts, consistent groove depth!

It was just as good at 70um, and we got started. Very simple and easy machine to use, Sabine got the hang of it immediately and she had only cut a few records on the Fairchild previously.

We then played back what we did on a modified Pioneer PL-12D fitted with an SME 3009 series II improved tonearm and an AT-12XE cartridge and converted it to digital. Here it is:

https://soundcloud.com/diskrecording/sets/direct-to-disk-analog-rek-o-kut-the-casio-sessions

Better than I ever expected of this setup! It really fits well with the Casio mood...!

All in all, a very successful, satisfying and rewarding restoration job. The Rek-O-Kut Imperial II is a wonderful system, capable of very good results for a system n this class. It is also very easy to use and can be found for reasonable money, it is ideal for the novice, the hobbyist, or even the professional with a certain lo-fi aesthetic and not very high expectations. This machine is now with its current owner, I hope he takes good care of it.
~~~ Precision Mechanical Engineering, Analog Disk Mastering ~~~
Agnew Analog Reference Instruments: http://www.agnewanalog.com

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grooveguy
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Re: RekOKut Imperial II restoration project

Post: # 49140Unread post grooveguy
Sat Jan 27, 2018 8:59 pm

Good work, Jesus,

Commendable results there. It's not clear whether you are cutting polycarbonate or embossing. Can you clarify, please; let us know what stylus did that demo, and what's your source for the blanks?

I do hear a characteristic 120Hz 'mechanical hum' component in the playback, which surprises me... if you are using the R-O-K turntable for both recording and playback. Yours is identical to mine, and I've always been very impressed with how quiet that table is. Maybe you have some hardened rubber mounts or something.

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jesusfwrl
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Re: RekOKut Imperial II restoration project

Post: # 49262Unread post jesusfwrl
Thu Feb 08, 2018 2:10 pm

Grooveguy, many thanks!

It is actually mostly 100 Hz that you are hearing, and a bit of 50 Hz lower down. The Rek-O-Kut (both the motor and the amp) was operating from a 60 Hz supply, so it is not from there. It is from the turntable I used to reproduce the disk, which uses a 50 Hz synchronous AC motor, which indeed has hardened rubber mounts. Another item on the todo-list...

The 60 Hz component is about 20 dB lower down, and the 120 Hz even lower. So the Rek-O-Kut is indeed quiet!
To be more precise, the spectrum analyser shows the 60 Hz component at -48.6 dB and the 120 Hz component at -52.7 dB, both relative to a 1 kHz sine wave tone at 7 cm/s peak lateral velocity. These measurements are unweighted, and reflect what was actually cut on the disk at 60 Hz and 120 Hz. This would be a combination of mechanical noise together with hum from the amplifier, and possibly the stray magnetic field leaking from the power supply transformer and motor windings, being picked up by the cutter head, or by the spring reverb transducers, or both, since everything was in close proximity.
A weighted measurement according to DIN45530 (1971), IEC60298 (1987), etc, would produce substantially more flattering figures.

I used a variety of blanks and styli for the fun of it, but the one used for the cuts you are hearing is a 5-year-old Apollo lacquer disk, cut with a Capps jewel stylus. The Rek-O-Kut arrived with 23 boxes of ancient "Audiodiscs", which I found to be unusable. Just a sticky mess, perfect to ruin a stylus. No idea if they can be restored somehow, but they went together with the machine anyway, so not something I would be doing anytime soon. I personally prefer to use lacquer for testing a machine in unknown condition, as any form of experimental blanks simply introduce even more variables and unknown factors.
~~~ Precision Mechanical Engineering, Analog Disk Mastering ~~~
Agnew Analog Reference Instruments: http://www.agnewanalog.com

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basplin
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Re: RekOKut Imperial II restoration project

Post: # 54012Unread post basplin
Sun Sep 01, 2019 11:39 am

Jesus - beautiful restoration! very meticulous and thorough.
Jesus, Grooveguy, et al. - what sort of lubrication is recommended for the overhead? It seems like it would be wise to put something in the gears on either end of the feedscrew. The ROK manual says to use "Rek-O-Oil" on the Guide Bar and Tie Bar....what sort of oil was this/what do you use here?

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grooveguy
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Re: RekOKut Imperial II restoration project

Post: # 54013Unread post grooveguy
Sun Sep 01, 2019 1:09 pm

I'm of two minds regarding lubrication; 'yes' on the gears and bearing surfaces, but only 'maybe' on the leadscrew. For gears and bearings I use a 40-weight (whatever that means) non-detergent automobile motor oil. Traditionally a heavier grease was used on gears, but I find that it simply gets pushed out of the gear teeth and eventually becomes a hardened mess on the sides of the gears. I put on just enough oil to 'wet' the surfaces, never so much as to drip.

The ROK (and other lathes) use a steel leadscrew and a brass half nut, although it's more of a half-tapped bar than what one would generally call a nut. Those surfaces are friendly to one another, and because the rotation is so relatively slow, and the rest of the overhead quite compliant (easy to push), I don't oil my screws. Even light oil will attract dust, and you don't need big ol' boulders in those grooves. Just the occasional cleaning with mineral spirits and an old toothbrush, and then run dry.

Not sure where you guys are, but in the US you can purchase a notorious lubricant called "Motor Honey." Going back as far as when I was in high school, this was something you could use to fill the crankcase of an old clunker you wanted to sell quickly. The stuff is so thick (much like its bee-produced namesake) that it wouldn't sneak by the piston rings, and the car sounded good and wouldn't smoke. I use that stuff in turntable bearing wells. One old broadcast table I've got has a lot of play in the main bearing, and when the bearing is dry you can actually rock the turntable from side to side a tiny bit. But with Motor Honey in the well, it's as solid as can be.
Snap3.jpg
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basplin
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Re: RekOKut Imperial II restoration project

Post: # 54014Unread post basplin
Sun Sep 01, 2019 1:51 pm

Great info - that’s a good point about oil being a dust magnet for the leadscrew....don’t want that. I’ll just apply it to the gears then. Thanks!

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jesusfwrl
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Re: RekOKut Imperial II restoration project

Post: # 54025Unread post jesusfwrl
Tue Sep 03, 2019 1:20 pm

basplin wrote:Jesus - beautiful restoration! very meticulous and thorough.
Jesus, Grooveguy, et al. - what sort of lubrication is recommended for the overhead? It seems like it would be wise to put something in the gears on either end of the feedscrew. The ROK manual says to use "Rek-O-Oil" on the Guide Bar and Tie Bar....what sort of oil was this/what do you use here?
Basplin, thank you for your kind words! I prefer to use SAE10 monograde oil, or one of the more specialized machine oils used for precision instruments and machine tools. Have a look here: http://agnewanalog.com/products/lubricants.shtml

I lubricate the guide rods, gears and leadscrew, so they are coated in an oil film but not drip. Before each use, I wipe off dust and old oil and apply fresh oil.

Running the leadscrew dry will accelerate wear, so I wouldn't recommend it. But, yes, it will attract dust, which you will need to wipe off.
~~~ Precision Mechanical Engineering, Analog Disk Mastering ~~~
Agnew Analog Reference Instruments: http://www.agnewanalog.com

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helloheathen
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Re: RekOKut Imperial II restoration project

Post: # 54838Unread post helloheathen
Mon Jan 20, 2020 4:57 pm

Amazing thread- Thanks so much for posting in such detail about the project. I have an 8DG and 6N - I am about to get my first ROK from PIAPTK sometime next month. So this thread helped a lot with understanding some issue I may face in the future with adjustments and dialing things in.

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jesusfwrl
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Re: RekOKut Imperial II restoration project

Post: # 54848Unread post jesusfwrl
Wed Jan 22, 2020 11:55 am

Many thanks, helloheathen, I'm glad you found it helpful! Enjoy your new ROK! What model is it?
~~~ Precision Mechanical Engineering, Analog Disk Mastering ~~~
Agnew Analog Reference Instruments: http://www.agnewanalog.com

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mrd
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Re: RekOKut Imperial II restoration project

Post: # 55148Unread post mrd
Tue Feb 25, 2020 8:36 am

This is amazing and really helpful.

Can I ask if the Audax head is weirdly light? I'm finding I'm having to add a load of weight to the counterbalance for a 1C am I missing something or doing something stupid?

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Vhflores
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Re: RekOKut Imperial II restoration project

Post: # 56561Unread post Vhflores
Tue Aug 18, 2020 9:14 am

Hola, felicitarte por el trabajo que realizaste con tu Rek o Kut; tengo un equipo idéntico con el amplificador R8B.

Mi primer corte lo hice con una laca Audiodisc que llego con el equipo y conecte un 1200 Mk2 directo a la entrada phono del R8B y los volumenes de entrada y salida de forma que no llegue a saturar el VU del R8B
el resultado salio bien, pero el volumen que registro es mucho menor que el vinilo original.
Como puedo mejorar el volumen del corte?

P.D. el R8B en la parte posterior tiene opciones a 16, 8 y 4 ohmios, lo conecte a 8 ohmios.

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grooveguy
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Re: RekOKut Imperial II restoration project

Post: # 56563Unread post grooveguy
Tue Aug 18, 2020 12:00 pm

En Español:

Hola señor y bienvenido al grupo. Lamento que mi español sea bastante pobre, pero estoy usando Google Translate para responder. Creo que obtendrá más respuestas a las preguntas si primero traduce al inglés con esta misma utilidad gratuita. Me sorprende que funcione tan bien como lo hace. En respuesta a su pregunta sobre el volumen, un grabado de laca siempre es un poco menos ruidoso que un disco de vinilo prensado debido a la naturaleza de "recuperación elástica" de la laca. Sin embargo, si su nivel de grabación es considerablemente más bajo,> 3dB por ejemplo, intente empujar la cabeza con más fuerza. Puede ser que el medidor de VU del amplificador no esté calibrado para la sensibilidad de su cabeza. El cabezal Audak es bastante eficiente, al igual que el Presto 1D, y requiere una potencia del orden de unos pocos vatios, excepto en picos de música. También podría ser que su cabeza necesite atención si, por ejemplo, la armadura se ha derrumbado contra uno de los polos del imán o el material de amortiguación se ha secado.

Y entonces en ingles:

Hello, sir, and welcome to the group. I regret that my Spanish is rather poor, but I am using Google Translate to make this reply. I think you will get more responses to questions if you first translate into English using this same free utility. I am surprised that it works as well as it does. In answer to your question about volume, a lacquer engraving is always a bit less loud than a pressed vinyl disc because of the "springback" nature of lacquer. However, if your recording is considerably lower in level, >3dB for example, try driving the head harder. It could be that the VU meter on the amplifier is not calibrated to the sensitivity of your head. The Audak head is quite efficient, much like the Presto 1D, and requires power on the order of a few watts, except on music peaks. It also could be that your head needs attention if, for example, the armature has collapsed against one of the magnet poles or the damping material has dried out.

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jesusfwrl
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Re: RekOKut Imperial II restoration project

Post: # 56590Unread post jesusfwrl
Sat Aug 22, 2020 1:23 pm

Mrd, thanks. The Presto 1C is heavier than the Audax, but not that much as to radically change how the machine should work. The type of stylus and blank may make more of a difference, as will the condition/adjustment/lubrication of the pivot points of the suspension.
What blanks/stylus are you using and how deep are you cutting?
Vhflores, if the output tube bias is incorrect, the R8B will clip (distort) earlier than it should. As grooveguy wrote, it could also be that the VU meter is not calibrated, or that there’s an issue with the head itself. Or, all of the above!
Even if all works perfect, these heads will not go as loud (without distortion) as the more modern stereo heads used to cut masters.
~~~ Precision Mechanical Engineering, Analog Disk Mastering ~~~
Agnew Analog Reference Instruments: http://www.agnewanalog.com

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mrd
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Re: RekOKut Imperial II restoration project

Post: # 56596Unread post mrd
Mon Aug 24, 2020 5:15 am

jesusfwrl wrote:
Sat Aug 22, 2020 1:23 pm
Mrd, thanks. The Presto 1C is heavier than the Audax, but not that much as to radically change how the machine should work. The type of stylus and blank may make more of a difference, as will the condition/adjustment/lubrication of the pivot points of the suspension.
What blanks/stylus are you using and how deep are you cutting?
Vhflores, if the output tube bias is incorrect, the R8B will clip (distort) earlier than it should. As grooveguy wrote, it could also be that the VU meter is not calibrated, or that there’s an issue with the head itself. Or, all of the above!
Even if all works perfect, these heads will not go as loud (without distortion) as the more modern stereo heads used to cut masters.
Thanks for the reply. I switched out the 1C for a Grampian type D and seems better but perhaps it's still down to my own inexperience in the setting up procedure - followed the manual to the letter but still struggling without adding weight to the counterbalance otherwise it's like it's really digging in. Tried with tungsten embossing cone, embossing saphire (should I be modifying the mount for a different angle?) and transco diamond. All myshank blanks. I'm not sure how best to measure depth of cut but I'm a long way off with anything that sounds good - and I've tried having more weight and deeper as well as easing off to the point that it's not a trackable groove - not entirely sure where I'm going wrong so I'm just keeping at it and trying to fathom it hoping that I have a sudden realisation that I've been being a bit stupid.

Re. the machine itself I need to send you an email for a price on a part for a related issue - the capstan took some damage in transit so needs replacement and the lord grommets/isolators are not in the best of shape either which is causing the drive to be louder than it should

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Soulbear
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Re: RekOKut Imperial II restoration project

Post: # 56598Unread post Soulbear
Mon Aug 24, 2020 10:08 am

Mrd Wrote :-
" I'm not sure how best to measure depth of cut"
Hi There Mrd, do you have a Microscope??? The Vintage Lathe Microscopes can command a Considerable amount of £££££'s or $$$$$'s to purhase, but usually come with an Eyepiece Reticle to take measurements, something like this :-
EyepieceReticleSA112101.png
You could also purchase a cheaper Used Microscope and simpy buy a Reticle Eyepiece Separately, they are both readily available via the Bay and elsewhere and Pretty easy to come by. Or for even less money a Digital USB Powered Microscope using a Laptop to display the images like this :-
U.S.B. Microscope Image.JPG
Cutting with a 45deg Diamond, your cutting depth would be half the width of the Groove Measurement. Use the Lathetrolls Forum search Function :wink: :wink: there's a Goldmine with lots of information contained here within the Posts about Groove/Depth of Cut etc just take a look and make a Search :wink: :wink: ....
Best Regards :P :) :D Soulbear
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mrd
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Re: RekOKut Imperial II restoration project

Post: # 56600Unread post mrd
Mon Aug 24, 2020 1:15 pm

Thanks so much for this Soulbear! I did do a search but overwhelmed with posts with those terms - much search harder. Yep, I do have a microscope but no reticule or stand with it (it's supposed to mount to my other overhead but that's a way off) and I find it tough to look through the eyepiece so like the idea of viewing on screen so have been considering getting a USB/HDMI one.
Soulbear wrote:
Mon Aug 24, 2020 10:08 am
Cutting with a 45deg Diamond, your cutting depth would be half the width of the Groove Measurement.
Ah yes, that makes total sense!

Since my earlier post have turned around the stylus (!) and getting much better results without added counterweight. Still sounds crap and very quiet and if I raise the level then that bleeds through to other grooves so I get some kind of fun delay (which I actually like for another purpose but not in this particular case)... all a learning process right?

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jesusfwrl
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Re: RekOKut Imperial II restoration project

Post: # 56637Unread post jesusfwrl
Fri Aug 28, 2020 8:02 am

mrd, Did you figure out how to connect the feedback winding on the Grampian? The Grampian will generally sound much better than a stock 1C, but requires much more power. What are you driving it with? The 1C/1D heads can be modified (as can most heads) to improve performance: https://www.lathetrolls.com/viewtopic.php?f=15&t=8576&p=54706#p54706

Depth of cut is best measured using a suitable measuring microscope. I can supply these if needed.

Do you have a picture of the spring assembly? I wonder if it's got the wrong spring, or if its deformed.

How is the head angle at the moment? Again, a pic would help. For embossing, myShank blanks are not the best way to go. Michael Dixon's blanks are way better, I've used them on several occasions along with his embossing sapphires, and as a bonus he's also a super nice guy!

Another thing that just occurred to me: is the entire counterweight assembly there? Any photos? Could it be that the actual weight is missing?
~~~ Precision Mechanical Engineering, Analog Disk Mastering ~~~
Agnew Analog Reference Instruments: http://www.agnewanalog.com

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