ok.. this is the 2nd half of the file about the little Turbo...i would love some comments and ideas about possible implemetations of the dac and other posibilities...
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The player is composed of two pcb boards, I will refer to this boards as top and bottom while the player is upside down. There is also a small PS pcb in the back corner.
Mod one: Opamp swap.
Open the player, take off all the small pieces of tape that hold the wires, remove the screws in the top boards and carefully push apart the top board so it lets you access the bottom board.
On the bottom part, you will find the soic8 opamp
http://www.rohm.com/products/databoo...df/ba10358.pdf It is located in the middle of the board between the cxdxxxx and cxaxxxx chips. Carefully use a desoldering braid to remove all the possible solder. Applying heat and using small flat screwdriver (that is how I do it if you have a better technique go for it!), from one side try to push the screwdriver under the opamp. It should come up easily. There is just one thing to keep in mind: do not force or overheat the pcb.
Once the opamp is out, get the one you like (I used an ad8620 overkill?? Yeah, probably, but it makes me happy) and carefully lift the #8 leg until it is horizontal enough so it will not touch the pcb. This leg will be used to feed the opamp straight from the players PS. Place the opamp in the board, solder the remaining 7 legs, use a small piece of electric tape covering the 3 legs and going under the lifted leg so it gets isolated and it is easy to access. Solder a thin wire to the lifted lead and run the wire to the PS, find the XX positive leg of the bigger capacitor and solder it there XX this allows the opamp to be fed with 5v, not the 3.xv you get from the bottom pcb.
Mod two: Capacitors.
I paralleled (2) 470uf axial nichicons I got from radio shack (you can obviously use better ones, if you wish) run a pair of wires to the battery compartment (you will lose the battery capability since the room will be used to accommodate the caps. Though you will still be able to use an external battery pack, (if you wish.) and connect the wires in parallel with the 150uf cap in the player. Or replace the 150uf cap with pp film bypasses and connect the caps from the battery compartment to the leads of the pp films. BTW: I recommend removing the old caps. As the units are old, the caps may have become dried out.
You can also play with the decoupling caps at the headphone out (in back of top pcb, 2 small 100uf nichicons). Try something in the 220-470uf range. Of course, check for fit, first.
Mod 3: The Turbo: paralleling the dac chip.
By doing this mod the player will became a dual dac player, fancy name but wonderful sound. This mod will make the player sound TOTALLY different
In order to do this mod, you will need a spare player to scavenge the pcm66p dac chip or order one from Partsolver.com and parallel it (using the piggyback technique) to the player you are modifying.
I am assuming you have the pcm66p chip already out of the board and ready to be installed
First thing to do is to clear the area in the top pcb where the chip will be installed and where the soldering iron will get close to avoid burning the ribbons and cables.
The most difficult part of this mod is to adapt the extra chip so it can be piggybacked:
Using a flat long nose pliers squeeze the legs of the chip until they are flat (yes you are reading right, make the leads of the chip straight) then find a way of making the leads to go down and straight (I use a piece of glass(window) and carefully push one side of the chip against the glass until all the leads are in the down straight position)
imagine this is the chip with the straightened legs (chip view from front)
____
--| |--
and these are the leads down straight
_____
| |
| |
Now the down straight adapted chip leads are just barely long enough to touch the ones on the DAC chip installed on the board. Once the chip is placed on top
Something like this
________
| 1 dac |
------------
| 2 dac |
/ PCB \
Recap: get an extra dac; flatten the pads; bend the leads down; place it on top of the other chip.
Now, all you have to do is solder each pad to the one from the chip below. Take your time and remember it can be done. Once you think you have finished, get a multimeter and check from the top of the upper chip lead to the pcb for continuity, I usually miss 3 or 4 and have to redo them is time consuming, but you have to make completely sure they are all soldered. Remember to solder the white cable back.
Use 5mm wide copper tape to shield the dac, cover it with tape solder a wire on top of the tape and solder the other end of the wire to the copper piece that shields the ribbon from the laser unit.
Now you will realize the dac sticks out a bit and you will have to force on the cover plate...there is an easy trick to fix this problem: If you take the top pcb out, you will find a small piece of metal in the front of the player (between the display and the bottons) that is used to keep the top pcb straight and also to accommodate a screw, if you rip that piece of (yes, rip it off, twist it until it breaks, bent in down..whatever..just get rid of it.) now the top pcb can flex just enough to let the cover push the prominent duo (dacs) down and will let the cover be flat and nice.
Some info about paralleled dac can be found at:
http://www.diyaudio.com/forums/searc...der=descending
Mod 4: external power supply :
The ps is basically the one from PPL:
http://www4.head-fi.org/forums/attac...&postid=225603
It is powered by a 12vdc@1amp wallwart. You could use a 9-12vac wallwart and a diode bridge/input caps.
There are other possibilities. Just use a good ps. The Turbo deserves it.
Mod 5: assorted mods:
-Using blueTak for the crystal: get a nice piece of bluetak in the bottom side of the top pcb you will find the crystal oscillator, lift it up carfully and apply a big chunk of bluetak around..
-Get a piece of green adhesive paper (linoleum kinda thing, friend gave it to me so I dont know where to find it...sorry) and cover the bottom side of the cd players lid.
-Use little adhesive rubber tips thingies as isolation devices; put 3 in the bottom of the player 2 in the front 1 in the back, in an unequal triangle. They will help dampen some of the absorb vibration and make the player more stable and less slippery.
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m.
D25s Turbo (mods comments and ideas)
