The rebuild of the ORACLE DELPHI MK1

[SonicArt]

First up, this is my table, its a personal rebuild and one I thought I would share with the SNA community, its not a commercial product, in fact being 45 years old I guess its a vintage rebuild   On with the fun...

 

I scored this table in excellent condition, although it had been badly serviced and had some of the usual issues (sticky bearing sleeves amongst others) the basic table is very clean and unmolested. I have missed my Mk1 for over a decade now, and always wanted an original Delphi again, this time I wanted to keep it looking exactly as Oracle designed it, on the outside at least but I wanted to upgrade everything I could that cannot be seen, to as current a level as permissible.

 

So I will start with a photo of the old girl, it has a Mk5 acrylic mat sitting on the platter in the photo, I will be using this as its an excellent mat, genuine Oracle, and it doesnt detract from the visual look. The old sorbethane rubber mats go off over the years, get pitted, sticky, scruffy looking, and dont sound as good anyway.

 

[mkaramazov]

Look forward to watching the progress of this interesting rebuild! 

[SonicArt]

First thing to do was look at the bearing, like many early Oracles, it had run a little dry up top. The issue with the first bearings was no gasket in the base plate, the ceramic thrust disc is a very good fit, but its not air/fluid tight. The instructions tell you to oil up the shaft and to do a re-oil every 6 months. We can all guess how many tables missed their 6 monthly service

The end result is the upper bushing gets tight, on a tight bearing you can usually see tiny fibres of teflon showing (the bushes are a composite of various materials which have changed over the years, until the introduction of the teflon needle bearings) and the bushing needs to be honed very carefully and evenly in order to regain the micro clearance needed.

 

A tight bearing, for those wondering, slows the platter down, as the table is driven by very quiet low torque motors, adding in friction increase the load on the motor, sometimes to the point where it can be worn beyond serviceable, good example is the Mk3 which already had an inherent issue with speed fluctuation (after a long time of use mind you) add in a tight bearing and you accelerate the wear on the motor drive.

 

Give an Oracle platter a light spin (no belt) and it should do 4-5 rotations minimum, this one would do 1-2 only. The Mk3 I just finished would not do one rotation! the bearing had to be pushed onto the shaft, but thats for another thread in the dealer forum, if you want to read about the Mk3 rebuild you can find it in my dealer forum.

 

So on with the Mk1 bearing, after careful honing of the upper bush, the platter spun freely for a long time! a light spin would get 7 revolutions un-lubricated.

 

Now to convert the bearing from "lube it every 6 months" to an oil bath solution like later models. What I do here is machine the bottom cap so that I can fit an o-ring around the ceramic thrust pad, in the past owners would cut a paper gasket to try and seal it, this worked to a large extent, but it always ended up seeping over time. With my rubber gasket in place the bearing is sealed well enough to hold isopropyl alchohol, so oil should be no problem

 

Pics show the base of the bearing and cap with the thrust pad, machined groove and o-ring in place. Now with the bearing full of oil the platter spins for quite some time   First job out of the way...

[SonicArt]

Second job I did was an upgrade to the record clamp. The original clamps are simple alloy knob with an alloy spider disc floating on the knob shaft with a circlip. Works fine, but Oracle refined it a lot over the years, delrin insert into the knob to isolate the alloy parts from the spindle thread, rubber o-ring inserted into a groove around the periphery of the spider to help decouple it from the record. Of course buying a new clamp would give you the best overall upgrade but all the parts these days are diamond cut and laquered, very different in looks to the original MK1!

 

So another hidden upgrade emerges I could have machined out the old knob, but then it would have been useless if it didnt work out! So I made a new knob with a brushed finish, I am going to investigate getting a duller brush finish but for now it looks quite nice. I dont have knurling tools, never needed them, so cannot knurl the outside of the knob for now.

 

The knob is recessed to take an original Mk5 clamp insert, something I found in my box of parts that I dont remember anything about! I popped a helicoil into it, and used M3 screws which sink down slightly below the surface of the delrin, no contact of course can be made here, the idea is the delrin insert isolates the spider from the knob and the knob from the spindle.

 

The spider is a little smaller in OD compared to the modern clamps so I couldnt attempt to groove it for a peripheral o-ring, probably for the best as it would be easy to stuff it up

 

[josh0571]

The original Delphi. After all these decades still one of the best looking turntables ever made. What a stunner!

 

Good luck with the rebuild!

 

 

 

 

 

 

[SonicArt]

Next up, bringing the legs into the 21st century! Whilst the looks of the Delphi were ultra modern at the time, and still as Josh says, a stunner under the skin there were areas that could be vastly improved as technology and materials evolved. The Mk5 saw the leg pillars go to solid delrin, a large isolation benefit as it works as a mechanical filter, breaking the path of the high frequencies to the subchassis.

 

I want to keep the table looking original, replacing the upper alloy sections would not be a good look, so focus needs to be on the lower section of the leg pillar. The Mk1 used a simple long threaded rod, the bottom threads into the base cup, through the chassis, and into the foot. The upper section holds the spring support grommet and allows adjustment up and down to level the platter once the springs are set to the optimal tension for each post.

 

After measuring it out and some quick drawings I came up with a solid base post that uses long grub screws in the same imperial thread of the original parts. Obviously the screws are isolated from each other inside the delrin, hence the mechanical filter.

 

Photos show the original leg assembly, the new delrin assembly, and the posts, old and new...

[SonicArt]

Decided to make an armboard last night as the MO is to make as much as possible in house for this restoration. First and last time I part off 100mm diameter alloy rod

I could have made it in Delrin, but Oracles armboards have been solid alloy for years now so went with alloy.

 

I didn't have a factory one on hand so worked on the Spiders ID and OD diameters, and poetic license! The top section is a solid disc, thin top lip of 3mm with a depth into the Spider ring of 9mm. The lower ring is, a ring! hollowed out and stepped a couple of mm to align into the spider's ID, it will be threaded and the top will be bored and countersunk, the two halves clamp together around the spider. Arm hole will be interesting, I need a cutter for the mill anyway so looks like time to source one thats adjustable for a range that suits the average arm...

 

[SonicArt]

Finished off the armboard tonight, perfect fit, once its cut for an arm a final brush finish to get rid of any marks!

 

Now waiting on light globes so I can replace the dead ones in the control panel, cannot go any further until they get here, a very odd voltage and size, I had to order them from OS.

[SonicArt]

A little more progress this evening, managed to steal some time and modify the original feet and add the Delrin footers. Mk6 saw a new alloy foot that was tapered a little and hollowed out with a Delrin footer riding on the threaded rod isolating the base from the shelf. These are available as upgrade feet for earlier models but again, I want to keep this as original in appearance as possible, and make everything in house.

Pics show the original feet, they are threaded onto the pillar base rods and used to adjust the level of the deck. You can see one has been bored out ready for a footer.

Second pic shows the finished feet, the footers are very subtle, just visible enough to be able to rotate them by hand for levelling.

 

My globes arrived today too, so time to rebuild the electrics. Popped the globes onto the board and re-assembled the control panel, fitted it to the deck, wiring in place, motor mount back in, motor has been cleaned and oiled both top and bottom bushes.

Motor in, some of the ribbon wiring was broken from age, so cleaned the ends up and resoldered it all, assembled the legs so the spider could go on for a speed test!

 

I let it run for 15 mins after setting the speed initially, it had wandered only 0.1rpm which was promising! After 30 mins it was holding good speed, a quick test with phone gave me a +/1 of around 15% and wow of 0.06%. Not bad for a motor thats 40yrs old and a belt thats not actually original! (didnt bother pulling out a new one yet as it all has to come apart again for doing the arm board and proper suspension tuning).

 

So its getting there! Looks as sexy as the day it was released, looking forward to hearing it now!

Edited March 6, 2023 by SonicArt

[Rdstreicher]

Glad I found this thread as I just acquired this table. Unfortunately it has been a bit abused and neglected, but this stray now has its forever home! 

[SonicArt]

Good stuff Ron, will be following your rebuild, yell out if you need help with anything!

[stevoz]

I have read that Oracle TT's had motors supplied by CEC. Can you confirm if this is the case with your Delphi? Just out of interest.

 

Also, here is some pic's of the CEC FR-XL1 turntable many from years ago.....some similarities to your gorgeous TT? At least in the tripod legs.....albeit much chunkier.

 

 

I wish CEC would make turntables again.

[Rdstreicher]

Do you aggressively polish the aluminum? or is there a clear coat over it?

[SonicArt]

I use Oracles own cleaner, you will get a bottle with the maintenance kit, microfibre cloth and their cleaner usually brings it up nicely. The early stuff has brushed finish, I was never sure on the leg housings and parts as to whether it was coated, it certainly doesnt look like it, funny all these years I never asked Jacques about it! Might ask him now..

[SonicArt]

21 hours ago, stevoz said:

I have read that Oracle TT's had motors supplied by CEC. Can you confirm if this is the case with your Delphi? Just out of interest.

No pretty sure they used pabst motors in all the early ones, not sure on later models as have not had to pull them down for any repairs.

Yes I know the CEC tables, would be nice to have one of those! Having imported a lot of CEC transports etc for many years I have a thing for CEC, I have a BD7000 which I will do a thread on at some stage, their top model from the late 70's (afaik). Great table, one I use a lot due to the auto return!

[Doppelganger]

22 hours ago, stevoz said:

I have read that Oracle TT's had motors supplied by CEC. Can you confirm if this is the case with your Delphi? Just out of interest.

 

Also, here is some pic's of the CEC FR-XL1 turntable many from years ago.....some similarities to your gorgeous TT? At least in the tripod legs.....albeit much chunkier.

 

 

I wish CEC would make turntables again.

Never seen that CEC before. Stunner!

[SonicArt]

Rest of the caps I needed turned up today, so finished off the "stabiliser dynamique" with a refresh. The cap in the main power supply was also replaced, I had planned to do this and Oracle also suggested it when I was chatting to them.

 

I noticed when running the table to test motor stability that the 317 was getting quite hot in the stabilizer circuit, so popped a clip on heatsink onto it while it was open.

 

 

Edited March 10, 2023 by SonicArt

[HdB]

Another simple upgrade -  if you build a much higher quality power supply it will make quite a difference (and yes, I know it's just a little motor and all that fancy stuff can't possibly change anything)

 

Just try using a good quality regulated lab supply and be surprised! 

[SonicArt]

Yes I have built quite a few linear power supplies over the years for the early tables, 24vdc is all that's needed, the Isolater puts out 24v and is an early attempt I guess at an improved supply. I want to keep the original with the table, I likely wont use it but its all fresh now

[SonicArt]

Just a note to anyone wanting to try refinishing their alloy parts, all the legs, clamp etc on the early models are anodised in clear, so best not to do anything to the surface other than cleaning it well. The Oracle cleaner works really well, its great for all the surfaces and comes with a maintenance kit.

[Rdstreicher]

I am currently on the road for work and am missing my project MK I! Any progress on yours? 

[Rdstreicher]

How do you think this table compares to a Thorens TD126 MK I?

[SonicArt]

I personally would rather have the Oracle over a Thorens, I know the Oracles well, they are very upgrade able, cannot go past the look, and they always seem to perform well, old or new.

 

Got my hole cutting tool this week, I stumbled across this Aussie made tool, its made for farm use, for cutting big holes in steel farm equipment!

Its a little agricultural but a little work and some test cuts in wood got me to within 0.03mm diameter on the armboard hole I wanted. Its designed to run into a 1/2" pilot hole, so really made to cut bigger than 13mm. I decided to cut a 23.5mm hole aka Rega size, as I planned to pull the Origin Live ZEPHYR  arm off another table to use with the Delphi while I think about modifying the Excel ES801 so it can support the arm tube at rest from its own baseplate.

 

So here is a quick pic of the tool in action, it cut quite well, bit of fluid to keep it under control and it needs a slow speed, 300rpm or so is best. It will cut up to 40mm dia holes with its 2 step body, and you can get an add on fitting to go even bigger. I think it might be time to look at opening the holes up in the FREYA case a touch so I can fit the Shuguang CV181-z tubes in without using risers....

[SonicArt]

After cutting the armboard I assembled the table so the legs could be adjusted and springs set up to suit the arm weight. A couple of hours later and she was ready for a test run, sounds pretty good too!

 

There will be more adjusting to be done and more little tweaks to the table in general over the coming weeks, and I will look at  wiring the Excel arm with Cardas and making a new lift/tube support plate for it so it can fit an Oracle. As its a small diameter base all I need to do is knock up a sleeve for the armboard, makes it easy to use the one board for various arms.

[Rdstreicher]

She is a beauty!