Panasonic SJ-MR100 Notes

I picked up a Panasonic SJ-MR100 for 100 Yen in Akihabara about a year ago. It was sold as junk and came with no accessories. I figured it might be fun to play around with, and I have some minidiscs I recorded a few years ago I wanted to try.

The player/recorder came with no battery/charger. So I hooked it up to a bench supply. I used the internal “gumstick” battery terminals. You can hook the positive supply to the door and ground the internal part of the case. Not ideal, but works for testing. I used about 1.4V. 1.2V will trigger the low battery warning. It draws quite a bit of current when spinning up the motor, so a current limit of 700 or 800mA seems to be required.

When I tried my first few minidiscs they appeared to be playing, but there was no sound. At first I thought the drive was faulty. However, I now suspect this is because they were recorded as MDLP (I don’t know for sure, but I vaguely remember that I used MDLP frequently). The SJ-MR100 was released prior to the introduction of MDLP. It seems to try and play the disc but no audio is produced. The display shows the following (LP, mono):

During normal operation the display is as follows:

There’s a comprehensive review of this device which was hosted on aol. It’s unfortunately now only available via the waybackmachine. A pdf dump is here:

I also found the service manual online, local copy here: