BLDC motor upgrade board for CDM9/CDM12 transport or CD player
Couples of years ago, I designed a BLDC (brushless motor) driver board for my CDM9 transport, which could upgrade the original DC motor to the BLDC motor on the CDM9 (as well as CDM12 theoretically) pickup without replacing the server board.
Last week, a friend of mine sent an email to me, he was wondering if Iím still keeping some of the PCB. But I was so sorry; I donít have any of them now. So, I think the best way is to share the design idea and the schematics with you guys, in case somebody wants to continue the similar project, or just make it as a reference.
The type the BLDC motor was CDS8C. It was a standard 3 phase brushless motor which I took from a used CDM12.6 CDROM laser pickup. The good thing is that the CDS8C has the same dimension with the DC motor RF-300 which comes with the CDM9/CDM12 pickup originally. You can hook up CDS8C directly to the CDM9/CDM12 pickup without changing anything.
The basic idea is extending the DSP spindle server loop to the BLDC motor by implement a BLDC driver, such as ROHM BA6849FP. In order to keep no change on the original server board, I just made use of the DC motor drive signal (which is the output of the server board) as the input. Because of most of the CDM9/CDM12 server board use BTL power OP, like Philips TDA7073, as the DC motor driver, we can easily use a RC network to convert the driven signal to the differential input of the BLDC motor driver. However, the parameter of RC network has to be selected carefully to make the server loop gain within the suitable range of the DSP.
I am gonna post the detailed schematic and some pictures of this project for you to reference.
The BLDC driver board works fine. The sound of my CDM9 transport was promoted. All of the audible changing was positive, I believe.