EASY TO DO, LONG LASTING, EXTERNAL POWER SOURCE FOR YOUR MD
Thought I'd share my little invention, if you've had the same frustrating problem with a reliable long lasting power source for MD:
Just take two large D-batteries (1,5V) and place them together on top of each other (in an own made toilet paper cardboard tube with correct diameter for example).
Remember the lower battery's + pole must be in contact with the upper battery's - pole. So 1,5V + 1,5V = 3V, exactly what my MD recorder/player needs.
Then, find a cable that fits to your MD's DC input jack (you can test it works), cut this cable and you'll find two small cables inside. Cut away a bit of the plastic coating on the end of both and fix the first cable firmly to the upper battery's uppermost surface, the second cable firmly to the lower battery's bottom (glue or other method). Of course you can also buy this stuff (D-battery holders for example) from stores.
It is very important that all the cables and the two batteries have secure contact!
I was blown away by the results of my test period with this power supply: outdoors, indoors, for hours, without changing batteries! Try it!
Hope it works for you too, Best regards, MDHenry