It is very common for pianos that were updated with the Super Satellite speaker package to be sold without them these days, or for the Suitcase Piano top to be missing its bottom and placed on a heavy-duty keyboard stand instead. Since both of these pianos used a 5-pin DIN or XLR-style cable to connect with the original amplifier, the question almost always arises: how am I supposed to connect this thing to a regular amp???
The good news is that the Super Satellite system included a pair of 1/4" outputs as well, as did the later Janus I system. The original design was for Accessory 1 & 2 to be an effects loop, with #1 being "send" and #2 being "return". Since #1 (the top jack) is "send", it is wired straight to the pickups and has an output level similar to an electric guitar with zero amplification. Accessory #1 is functionally the same as the 1/4" out on any guitar or bass, and consequently you will need to use a guitar or bass amp to get the proper output (see above).
In the case that you have a Suitcase Piano top without the Accessory jacks, you will need to remove the plastic top and use the output from the RCA jack at the left end of the pickup chain. The cable you find inside can be unplugged easily without damaging anything, then you can connect an RCA male-to-whatever cable of your own in order to get output to an amp or mixer. Again, it's the same as a passive guitar output. You'll need some sort of preamp along the way to boost the signal no matter what.