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In Reply to: RE: Damping the Foating CDP Laser-Track Tray posted by Dryginger2 on February 20, 2015 at 17:07:24
older Harman CD player circuit.
Second is photo of laser assembly.
Harman had relatively sophisticated CD machines for its time and cost. Notice the copper shields on particularly noisy IC's. The DAC chips are also placed under the board to provide more of a ground plane and EMI isolation. You can see the outline of the chips on the top of the board.
The laser assembly shows the shield off. You can see the copper coils surrounding the lens assembly. On the large coils are two smaller coils on each side. I soak those coils in ferro fluid ( CAREFULLY!), not dripping. Most laser lenses assemblies have similar motor assemblies although the orientation may be different.
The next generation of HK machines were even more sophisticated with star grounds and special EMI casings (7450, 7600). Note all analog output stage. Suitably modded they could sound as good as a Wadia separate (IMHO).
Follow Ups:
Unclestu:
What kind of ferro fluid do you use (type/viscosity),
and where can it be obtained?
Many Thanks!
Dan
Dan,
I just let a pipe cleaner absorb some MG Chemicals 801B Super Contact Cleaner and applied its soft narrow bent head to all visible contact points and running connection lines of parts on the floating tray including around the vicinity of the laser. The dynamics and flow of the music now dance effortlessly as Uncle Stu describes so ferro fluid may well be the best long-term solution but it is not a short-term requirement for those wanting to use a contact cleaner instead.
DG
AN oblique shot of the laser head. A gentle push to the laser head will reveal that the copper colored windings will move up and down, back and forth. The white rectangle to the right of the picture, right of the lens is the hinge assembly.
The copper winding boxes a pole piece for a magnet, and there is an additional pole piece outboard both coil windings. It is on these coils that I add the ferro fluid. Care must be exercised as the pole pieces will attract the ferro fluid !
Idea is that the ferro fluid fills in the gaps between the coil wires and thus increases the magnetic intensity of the motor, strengthening the field and making it react faster to the servo correction circuit.
In experimenting with this, it brought to light the importance of the correction circuit for audio in all optical drive systems. It also showed how poorly designed most correction circuits are. There hasn't been a laser mechanism which did not show dramatic improvement by adding ferro fluid to the motor coils.
Caveats: ferro fluid is a colloidal suspension of ferrite in mineral oil. Spill into the laser well and kiss the laser goodbye: you can cnot clean it out. The mineral oil will eventually dry out. That being said the ferrite material will already be lodged between the coil wires, exactly where you want it anyway
Uncle Stu,
Have you heard the result of adding contact enhancer to where wires are soldered to the circuit board/ volume pot/ speaker output terminals/ case in an amplifier? Be interested to read your comments if you try it.
DryGinger
Uncle Stu,
You're 100% right! Lacked the understanding and nerve to mess intimately with the laser in order to access its coils as you here articulately describe so was surprised with the beneficial outcome of contact-enhancing every visible tray connector/connection.
Thank you for sharing outstanding tweaks that invariably inspire multiple ideas for testing in my brain. The outcome of one was unexpectedly and remarkably productive. Since it can be applied at virtually no cost to considerable sonic benefit by any audiophile, I'll start a new thread later to give it a higher profile.
DG
bought mine off ebay; no data. use very little!!1
Unclestu:
I find you work with the ferro fluid on the laser to be quite interesting!
Is it possible that you could start a thread where you would have 1 or 2
very close up pictures of the coils, and where exactly you are putting the
ferro fluid? A few arrows would also be good. It sounds like you are applying the fluid to the copper wound coils - is this between the coils and the magnets, or just on the coils (as in soaking into them)? Also, what do you use to apply the ferro fluid to the coils?
It sounds like the fluid you use is just something you found on e-bay... would you say that it is a typical ferro fluid as far as viscosity?
Many thanks for all you great tweak posts and in-sightes! I have worked
in the area of lab vibration analysis for decades, and an quite attuned to the concepts of damping movement, resonances, and vibration.
Dan
might take a while for photos. if you're patient I will eventually post.
I only soak the COIL assemblies. Since the correction motors move and can move a lot allowing too much ferro fluid to the point where it bridges the gap between the coils and the magnets or pole piece greatly increases the risk of splashing the fluid onto the optics. BIG NO NO!!! It is impossible to clean the mineral oil off(don't ask, but I've tried)
IF you place too much ferro fluid and you form a bridge, a piece of kleenex can absorb excess. I use a #5 stainless forceps to control the tissue, although you can fold it into into a triangle and apply.
Before placing ferro fluid, always analyze the motor assemblies. All laser assemblies have some kind of shield, usually plastic clip on.Remove to see the coil assemblies.Remember the lens has to move in two planes, so you may find four or even six coils. Each has to be loaded with about approximately equal amounts of ferro fluid (I've never been really critical because my mechanical dexterity is not so great these days.
If the laser motor coils are not overflowing but don't track well, I simply add more till I can see the ferro fluid build up in the coils themselves. The static magnetic fields will tend to hold the ferro fluid in place. Be careful as the magnets will draw the fluid straight to the pole pieces and magnets themselves. If that occurs I wipe the magnets and pole pieces clean to avoid bits flying off.
I used to use a diabetic insulin needle to apply the ferro fluid. Thin and it doesn't need much, but I do find it difficult to control the syringe itself. I use a toothpick these days and I actually have better control leaving a tiny droplet of ferro fluid on the very tip. As you approach the coils you can literally see the magnetic field "pull" the ferro fluid into the coils (power should NOT be on). HINT: move very slowly and carefully observe the tip and the destination...
Top photo is the common Sony KSM 2xx series.
Motor coils are large and easily accessible. Notice the larger square box is color coded copper and the two ring coils on each outboard side are coded gold. These represent the vertical and horizontal coils. All need to be soaked.
You can easily pull the motor coils to one side for greater ease of application. Even though applying from one side the ferro fluid will flow and usually equal out after a few seconds of playing (don't be surprised if sound is slightly distorted in the first few seconds.
Remember you want roughly equal amounts of ferrofluid on both sides,
Second photo is the ubiquitous Philips design CDM -12.
Motor coils are sandwiched between the magnet structure in a very tight position, Application is tricky as you need to approach from the front or rear accordingly (90 degrees to coil structure). Fluid will bleed to magnet so be prepared to wick away access
Great pics! Stu.
Sweet pics!
Uncle Stu,
Thank you for illustrating the coils via the picture.
Your mentioning the special EMI casings reminds me how in the case of this Denon the substitution of plastic for their brass covered stainless steel machine screws positively degrades audio and video. It not designed to have a domestic ground connection (no ground pin) and, given the number of small tingle shocks from the case, I suspect that all the circuit boards/ case use neutral as a ground alternative like space vehicles.
Never fail to be surprised how much inexpensive audio performance many manufacturers leave on the table because they exhaust intellectual bandwidth/ time/ money or are more concerned with engineering than sound quality.
DG
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