YouTube - MiniDisc Repair - Sony MZ-R700 - not writing - but it's not the write head...

The Sony MZ-R700 is a fun MDLP player from 2001 that came in some nice colors like a metallic yellow. It was a cheaper version of the MZ-R900 so it was plastic and used AA batteries.

I got one cheap on eBay that wouldn't power on and fixed that quickly by fixing the battery door contacts.

After that, it turns out that it wasn't recording at all!

Often with Sony recorders, that points to a write head failure (something along that delicate ribbon cable broke!) which can be a tricky fix.

To troubleshoot, I opened up the player and tried recording while pushing down the write head (GENTLY) closer to the disc. It worked! The disc was recording as long as I was holding the write head close to the disc, so it had to be some other mechanism - something to lower and raise the write head, perhaps?

After some research (and noticing a loose rod inside the device), it turns out I was missing a toothed metal gear that should be locking/unlocking the write head arm. This allows it to lower when recording, and raise when not recording.

Here's the gear and the toothed arm it moves from my "donor" MZ-R700

From the service manual
More from the service manual

So after realizing my gear was gone completely, I lucked out by finding out that a fellow MiniDisc user had a junk MZ-R700 that I could have! Hopefully it had the working gear - and it did!

After extracting that metal gear (the collar/c-clip holding it in place flew off into space!  Luckily, any small one from other MiniDisc gears will work), all I had to do was put it into place in the new one. 

It was a bit harder than it sounds because the gear is keyed to fit on a certain way (to prevent slippage) and because I had to figure out which position to leave the gear (and arm it moves) in. I realized after testing that after installing it, you'll want the gear to move the arm that allows the record head to drop down fully. It will then raise/lower it appropriately!

I hope the video helps!