Hacking Denon DCD-500

Just acquired a DCD-500 which has a PCM54HP R2R DAC.

The transport and controls look cheap and I suspect 25 odd years hasn't done them any favours. The slightest nudge throws the tracking off entirely.

I'd like to be able to use the DAC with a newer and more reliable CD player which has a SPDIF output. Initially just try it in situ and if I'm happy with it, build it on a new PCB down the track.

I've found what appears to be the PCM signal feeding a CX23035 chip which then drives the parallel R2R DAC.

So, how do I get from SPDIF to PCM? I found some chips which do the job, is that my only option or are there any pre built modules for this? If I use a chip how to build or find an optical receiver? Thanks in advance [emoji4]
 
Thanks for the pointers, these I think will be helpful.

However I had a thought in the meantime, I can probably tap the raw PCM stream in the other player without too much difficulty. If I install the dcd-500 board inside the case, that would be a reasonably elegant solution. It is unfortunately a single board, this being a low cost player (by all appearances)

Before I go to the trouble though, I might a/b this player (it does work, after a fashion) and see if it's worth the effort.