Chasing the Sony CX20084 speed chip for D6C walkman

One thing that catches my attention is how this circuit is powered: it's using the +11.2V rail from the DC-DC convertor and regulate it down to 5V.
The motor draws ~100mA with load, not sure if that DC-DC can actually supply that much extra current (without significant ripple) since it wasn't designed to power the servo or the motor, but just audio circuitry.

I think it's a better idea to power it directly from the 6V rail with some protection which has to be low-dropout given minimum supply voltage of BA6301 is 4.5V.

As for the FF/REW auto-off, that has to remain.

Wonder if the other Chinese replacement (https://www.goofish.com/item?&id=766454209480) is also based on the BA6301.
In this case only the IC is powered through a regulator from the 11V rail, not the motor.

 

I feel the same, I have already written off this board as a lab experiment in what NOT to do. Last evening I modified it heavily by connecting both motor and FG directly (contrary to Chinese instructions) and FG noise went way down. I also twisted the FG wires like a twisted pair to maybe reduce some motor noise. Finally I installed a (larger, throughole but more suitable) transistor and to suspend the motor from the 6V rail. I think LeKos forgot how weak the 10.8V rail is AND the motor noise you get in audio as well. He has a second problem, tying pin 5 of the CX20084 (or pad 5 with that chip gone) directly to 5V. Not sure how that works but it certainly exceeds the 3.15V(brown PCB) 4V(Green PCB) Electrolytic rating on that pin. My Chinese board has a trimmer that biases pad 5 between 0-5V (factory set to 3.65V). It’s totally unstable however. Sony indicates that pin as 1.65V. Any opinions on how to determine that?

I think the other Chinese board looks suspiciously like the Korhonen board for early brown PCB units only, where you must remove the components around the CX20084 as well to attach the board to the battery solder tabs. I think the solution (for later units anyway) will be a more rectangular board that fits in the bottom of the cabinet (top of the unit in use) beneath the DC-DC converter. At least on the D6C I have there is plenty (well some room down there.

 

It seems you are looking down on the Ba6301 proposal so much that you didn’t even bother to properly look into it, while also doubting Lekos's results. You also seem confused about the schematic provided by Lekos.

I would like to assert that the schematic is completely rational, fully compliant with standard specifications, and extremely close to the original diagram. It operates with 100% stability (I have been running the Ba6301 for two years now and it runs stably, even better than the original due to the high-quality capacitors and resistors).

And please note, so there is no confusion: the motor power is drawn directly from the battery and is completely unrelated to the 11V power supply. The 11V supply is converted to 5V solely to power the IC and serve as a reference voltage (which is why it doesn't drift and is extremely accurate, exactly the way the CX20084 operates).

I don’t know how the Chinese circuits are designed, but Lekos’s schematic is definitely the most perfect solution for even the ultimate perfectionist. It could have a simpler version where you just need to supply 6V battery power, 11V, and two pairs of wires for the motor and FG to get it running (omitting the speed adjustment and quartz lock functions, which do not affect Wow and Flutter).

Please look into it carefully and try it out—then you will see just how perfect the results are.

 

I assure you I do not look down my nose at the LeKos design or the chip he uses. I am in fact starting a project using it. I referred to the Chinese module I ordered as deeply flawed and I have reached out to LeKos with questions that came to me as I studied both his original and the knockoff. I think my concerns are genuine but will be the first to celebrate if I am wrong.

I do now see he tied the motor to 6V rail, I misunderstood and it was unclear from his schematic (the Chinese engineer tied it directly to 10.8v which was a terrible mistake. I hope I’m also wrong that LeKos is tying Pad 5 of the CX20084 to 5v, the cap on that pad is rated much lower.

 

Sorry about that, I lost my cool for a second.

 

No problem.. Did you build with his PCB? I am going to order a few and see if I can build it though I have little surface mount experience. Any tips gratefully accepted.

 

@Hn14197 Ok, I made a mistake regarding LeKos schematic: it's only the Chinese that has the mentioned problem. Edited my post to correct it.
But I think it's more helpful to just point out that I made a mistake, rather than assuming things about me: that I look down on people, that I look down on the BA6301 proposal itself.
Also never said LeKos solution isn't working or isn't up to spec (it's clear that it is, post #119 shows it), rather I was wondering why Chinese one doesn't since they are using the same IC.