79209

# 79209

Another restoration / transformation for a Thorens TD150 mkII

6/10/2010

Above photo: R7-2. A Thorens TD150 with some upgrades.

This page is an update to a project I worked on 5 years back. I'm not sure that I'm any wiser for these additional 5 years, but I do have some different ideas about how to approach upgrading the Thorens TD150. For one thing, I recently worked on another TD150 project that went very well. #34259 It went so well that I decided to duplicate those steps for my own project on this page.

The process:

Receiving_1a.jpg (78459 bytes) Receiving Inspection Note: this linked page was written 5 years ago. It details examination and analysis of the important parts of the turntable as it was then received.

Custom Plinth Dept.

First there is a 3D cad model called R7

Above: I drew this plinth design for project #34259. Let's refer to that as R7-1. It was offered to the client as an alternative to my previous concept drawing, R6. While the interior dimensions are compact and allow little space for components, I was happy with the sound of that deck, so I am using it again here. This time the color is different and there are some minor changes, but essentially this is the same plinth. I will dub this one R7-2.

Above photo: The plinth construction is by stacked layer build. 6 layers of 1/2 inch thick Baltic Birch plywood glued/pressed one on top the other. Coating is Acrylic Lacquer. Multiple coats. (10 +) Sanded between spray applications. It awaits final polish as I allow the lacquer to harden over the next few weeks. The heavy rubber feet are from Antique Electronics supply. These fasten by means of 1/4-20 machine screws going into brass threaded inserts that have been installed into the bottom of the plinth. This color (green) is a custom color that I had used 20 years previously on a '69 MGB that I had restored/painted. It is a custom mix. At the time I was going for mid 50's Jaguar British Racing Green. It's probably not exactly the right shade but it is what I had come up with back then. Having a full quart left over I decided to put it to use. So here it is :-)

hint: click on thumbnail to view image full size

Above photo: Looking inside: Like R7-1, solid ebony supports are used to mount the motor plate. Also, like R7-1, I am using spacers of solid delrin between the motor plate and ebony. The turntable assembles from above. There is very little access from underneath. To carry out maintenance the turntable chassis will lift out after removing 5 wood screws. The armboard will also lift out from above to access the underside for tonearm maintenance.

Above photo: A cutout for an iec socket is provided for easy power cable connection. The tonearm choices I am working with won't need an RCA jackplate.

Assembly and build method

It has already been established that the motor and platter bearing are in very good condition. Knowing this we can move forward to a simple assembly process.

Above photo: This model is a MKII TD150. It came equipped with with a tonearm cue mechanism that was operated from the front of the deck by means of cable and cranks. Those mechanisms were removed. There is a bracket to support the cue control. This is swaged into a hole in the motor plate. This was carefully removed. See above photo for location and to view the assembly after removal.

Above detail photo: The conical coil springs are replaced with the assembly shown in the photo. The result of this work still offers good isolation from the motor board, and all supporting surfaces. However There is no bounce. Consequently, the hanging sub-chassis holds position rigidly like a non-suspended turntable, yet Isolates from surface borne vibrations like a suspended turntable.

Above photo: The motor capacitor is replaced with a new one. Value is .33uF, 400 volts. The original cap was rated at 10% of stated value. The new one is rated at 5% of stated value.

Above photo: AC input connection. Care is taken to insure that the couplers won't pull off.

Above photo: Armboard to subchassis mounting. I am using .06 thick Delrin shims at the armboard fastener mounts. The purpose is to maintain a solid mechanical joint while providing a lossy filter between the subchassis and the armboard. The intent is to inhibit the flow of resonant energy between the subchassis and armboard. None of this supposition has been proven by any scientific measure.

Above photo. Looking at the assembly prior to adding platters, belt and arm.

The decorative aluminum top sheet has been replaced with another sheet of aluminum of similar alloy and thickness. The new sheet of aluminum is cut to the pattern of the old facia except left blank to cover the cue knob hole, then adhered to the steel motor plate using RTV sealer. The vulcanizing adhesive is spread evenly to the mating side of the sheet, then the facia and motor plate are clamped together for a period of 24 hours to fully cure. After that the top facia is in fact "vulcanized" to the motor plate. Finally, the facia is spray-coated in black "Hammerite" enamel.

Choosing an arm for 79209

6/8/2010

Above photo: looking at the possibility of using a Graham 2.2. It appears that it might work but mounting distance hasn't yet been determined.

For the moment the turntable is up on its maintenance jig during this fit-up session.

6/9/2010

Above photo: Now testing fit with the 'cut but unfinished' cherry armboard. Mounting distance is now correct. Noting that the vta adjuster overlaps the plinth. Fortunately, it has elevation clearance and does not touch the plinth....so far.

Armboard considerations

Above photo: Some nicely figured Cherry is found at a local Rockler's.

Above photo: Detail of the tonearm mounting holes.

Alignments

Checking the mounting distance

Above: checking the all important "pivot to spindle" distance using the Graham spindle adaptor. This is a very convenient method which makes the dimension easy to check while using one of Bob Graham's tonearms.

Overhang and Zenith angle are set per the Graham overhang gage then double checked with a TAD arc protractor specific to the Graham.

Site the turntable to best advantage

Above photo: making improper use of a Neuance shelf.

next photos: Making better use of the Neuance Shelf.

Above photo: inverted cones are placed on the heavy wooden support stand

Above photo: detail closeup of the cones. DIY style. Heavy rubber tapered footers placed upside down. Large brass acorn nuts are fitted within the relief diameter of the cone.

Above photo: Brass cones are threaded into the plinth bottom

Above photo: The Neuance shelf lies on top of the three inverted cones.

Above photo: The Thorens stands on top of the Neuance.

Above photo: another view. I suspect that one could refer to this style of turntable site method as being "light yet rigid".... from the Neuance up, that is.

Early listening:

6/11/2010

It is early but I am pleased with the sound of this little player so far. It exhibits a lively punchy sound character.

There is a tendency on my part to make comparisons between this player and my Teres 145, which I have recently heard using the same tonearm and cartridge. There are some large differences between these two very different turntables. The Teres excels at providing detail, articulation, very fine inner details, a sense of the space between notes etc. But it does this in a laid back manner that seems to lack musical energy. Particularly on rhythm heavy music. The TD150, by comparison provides good musical energy and that sense of toe-tapping drive on rhythm driven music. It also provides a fair amount of detail, articulation, definition and air, but not to the same level as the Teres. I attribute the differences in rhythmic drive to the motors of each player. The Teres is DC. The Thorens is AC synchronous. I would attribute the differences in detail retrieval to the platters and platter bearings, which are respectively very different.

More notes as I make them

6/13/'10

With further refinements made to the tonearm alignment, (azimuth and vta) and the above noted "light yet rigid" site methodology, sound quality improves. At this point the stock 16 pole synchronous motor is being fed ~ 80 volts ac from the Viz Iso-Tap isolated power supply. I was fortunate to receive this motor in excellent condition. It runs very near to absolute silence. On rock records the turntable has some visceral impact. Dynamic & slammy. If not exactly on par with its older brother, the TD124 that stands on the other side of the equipment rack, it holds its own in the rhythm & drive department.

Pink Floyd; "Wish You Were Here", track: "Shine On You Crazy Diamond" soared high and sang mightily. It is safe to say this little guy rocks out very well. I am also pleased with the performance of the Graham in this respect. It doesn't seem to be holding back on delivering any excitement. On Moody Blues' "In Search of the Lost Chord", track: "Departure", the opening synthesizer tone that starts low and crescendo's slowly up and ultimately high, managed to raise the hairs on the back of my neck,.... again. It is supposed to do that. A function of the turntable's getting the timing right to deliver that nice thrill.

I'm also getting some nice articulate inner detail. I've been playing through some of my classical library. Last night it was Mahler No. 2, Klemperer, Vienna Symphony, Beethoven No. 3 (Eroica) von Karajan, The Four Seasons, Vivaldi, Stuttgart Chamber Orchestra. All of this was involving and drew my attention into the music. Clarity, articulation, impact, decay. It's all working well.

At this point I'm not listening as critical as I might. In fact I would rather just listen to some records that I know. I believe this to be a sign that the player is delivering the goods on a very good level. It draws me in. Competitive with what, you say? Who cares, I say. It draws me in, that is what counts.

More notes as I make them.

Future mods:

On the short list of modifications to do, is the need to find a suitable motor controller that regulates frequency and allows adjustable output of voltage. A good frequency generator type of controller will deliver a precise wave form to the ac synchronous motor. This type of controller would eliminate the need for a motor capacitor, which is common on AC synchronous motors that run on single phase household power. The synchronous motor is a two phase design. But the power being fed to it is single phase. So, in the typical low cost scheme, a capacitor is used to 'fake' the motor into seeing a second phase and also time that second phase so that it is at 90 degrees to the first phase. "Whew". A good controller would eliminate the need for the 'motor cap' and entirely control the operation of the motor in a very precise, optimal way.

It is also important to have a level of isolation. This much I already have in using a Viz ISO Tap. By isolating from the mains I can eliminate much power supply "noise". My particular Viz Iso Tap also allows adjustable voltage output. That is part of the solution, just not all of it.

I will also study the potential for a bearing upgrade. This would involve designing and machining a more solid and substantial bearing housing. The housing would feature a removable bottom cap so that thrust pads could easily be replaced when worn. Similar to that of the TD124.

I have already experimented with subchassis replacements. I may try this again but with a slightly different view than I had 5 years ago when I built the first one that can be seen within the links below this text.

Trying out an SME 3009 S2 tonearm

7/3/2010

The heavy tapered rubber footers are installed again to the plinth bottom in preparation for the TT to stand over the heavy glass shelf of the audio rack.

A new armboard is cut for mounting the SME 3009 S2. For the present, it is finished except for finish coats which will be applied later. I want to hear this arm before and after finish coats are applied to the armboard.

The tonearm requires some maintenance to get back into shape. New coupling rubber is installed into the aft countertweight portion of the arm tube. This process goes easily and is helped by referring to the service manual for details of the procedure.

In order to fit this tonearm into my R7-2 plinth, which is compact in its interior volue, it was necessary to disassemble the standoffs that are used to mount the 4-pin phono cable connector. In this case the tonearm cables are allowed to hang from the pillar bottom of the SME, while the standard phono cable itself is tied securely to the interior of the plinth in order to prevent any potential for tearing/breaking the fragile tonearm wires. Otherwise, the tonearm remains as the manufacturer delivered it.

The cartridge is the Denon DL-103R with standard conical tip, installed into one of Uwe's ebony bodies. Some mass tuning is done by placing a brass shim between the cartridge and SME headshell. There is no problem setting vtf while using this additional headweight.

This model of tonearm is very easy to align and adjust. The supplied SME protractor is used to set overhang. A mirror is used to adjust azimuth. VTF is set using the electronic scale to a value of 2.4 g. VTA is adjusted, initially by sight. This is achieved by adjusting the arm pillar so that the arm tube appears parallel to the record surface while the stylus is standing in the groove of a stationary record. From there further tuning is done by ear. With the DL103-r cartridge, I tend to favor its sound with the cartridge body exhibiting a very slight forward tilt. SRA should be close to the preferred 92 degrees.

Listening notes:

This site method works to good effect. The heavy rubber feet over the glass platform is effective and does not impart any unwanted "harsh glassy" aftertaste as some might think it would. The heavy rubber feet do their job in isolating plinth from platform while maintaining a very solid stance.

This arm (SME 3009 S2) compliments the Thorens quite nicely. The Denon tracks very well every groove it traces. Sound is detailed, full bodied and sweet. Excellent low frequency impact. Slammy. Punchy. Upper frequency details are articulated cleanly. Whatever this arm doesn't deliver isn't missed. I like it.

Listening notes part 2: 12/2010

As good as the SME 3009 S2 was, I found myself missing the sonic bliss of the Graham/Jubilee. So back in it went.

The solid brass cone feet have been exchanged for ceramic cones from Golden Sound. I'm using their "Large" ceramic cones between the R7 and Neuance. I have the Neuance isolated from the audio stand by means of sharp solid brass cones fitted within the heavy rubber feet, inverted. This way the Neuance is pinned between 6 cones, 3 under, 3 over, and well isolated from the glass platform of the audio stand by heavy rubber.

I could leave this unit just like it is and be happy with its sound and appearance from this point forward....but I'm sure that sooner rather than later I'll get the itch to work on something new.

End

Previous notes: (from 5 years back)

The plan at that time:

Receiving

Receiving inspection
disassembly and detailed inspection
cleaning and repairs
fabricate new armboard
assembly with no modifications, adjustment

Step 2

Play and listen

Play the table for a time with no modifications
Compare the table to the modified TD160
Compare the table to the Teres

Step 3

Begin a systematic modification program

Maintain original suspended layout but with significant upgrades
armboard experimentation (different materials)
power supply experimentation (does the motor run smoother at 80 vac than 110 vac...?
redesign the plinth for greater rigidity and damping
redesign subchassis frame for greater rigidity and damping

Step 4

Listen to some records.

Step 1: Receiving

150frame_1.jpg (46869 bytes) Looking at the TD150 subchassis frame. Some notes and comparisons to its successor, the TD160.