This is the service manual of the Mattel Synsonics.
It includes the schematics and a troubleshooting procedure.

  Mattel Electronics
  Service Manual
  Synsonics Drums
  Model 5281
  1182 2M GMN

Courtesy of Steven A. Orth a.k.a. "IntelliSteve"
http://www.intvfunhouse.com/

This is http://www.teaser.fr/~amajorel/synsonics/README, last modified
AYM 2007-05-31.