Hi Joyce and welcome to JustAnswer,
Thank you for the question and your patience. Should you still need assistance for information purposes only...
Initially, have you tried using a pair of stereo headphones? ...or connecting to an external amplifier/speaker?
Still, please try using "...six 1.5V SUM-1, “D” size, R-20 or equivalent batteries...". This would serve as both an attempt of a fix and as a test by process of elimination.
The above are the only easy user doable tries.
If symptom persist even when using batteries, then it would almost always point to an internal hardware issue.
Are you then considering a DIY (do-it-yourself) repair approach? If yes, do you have access to and familiar with a multi-meter and even a soldering iron?
Equally important, could you make use of the repair/Service Manual or at the very least, the schematic diagrams?