We recently stumbled across a broken Marantz UD5007 Blu-ray/SA-CD/DVD/CD player for a really low price.
The previous owner reported the power supply to be broken, and a professional repair service had given absurd quotes for troubleshooting/repair.

When plugged into the wall, the player would only blink the red standby LED indefinitely and never turn on/make any noises.

Making our lives a lot easier here, the full service manual, including schematics and a troubleshooting guide can be found online.
I spent a bunch of time trying to diagnose the original switch-mode power supply (which is fairly simple), but due to lack of tools/equipment (away from our usual lab) I couldn’t get the original supply up-and-running again.

The service manual also included the supply rails & pinout of the low-voltage connector:

• +5V standby
• +5V
• +12VM (motor)
• +12VA (analog)
• -12VA (analog)

along with both

• PCON (aka PS_ON)
• GND

which is very similar to a regular PC ATX power supply:

We decided on the brute-force approach of cutting the old internal connector and just wired an ATX extension cable up to the motherboard using Wago 221 connectors:

A tiny picoPSU works perfectly well for the super low power requirements of the player (~20W).
The UD5007 can now be powered from a single 12V wall supply, using a barrel jack input.
You could also install a different small-factor power supply (like an ITX/SFX power supply).

And then it’s already back to its regular job of playing Finnish goth metal, wonderful: