Transplanted Philips drive - CD-R/RW question

Hi,

I recently transplanted the mechanism from an old Philips player into a Marantz CD63 (see https://www.diyaudio.com/community/threads/marantz-cd63-cdm-12-disc-not-spinning.398921/ )

In the Philips CD713 CD-R discs played fine (the machine is advertised to play CD-RW as well), but in the Marantz, though a CD-R loads quickly (TOC is read) it keeps cutting in and out during playback.

What's different? - the power the board is supplying to the laser?