Trying to fix a Lasko Tower Fan, Model 4920

The fan now operates only on the "LOW" Speed setting. Trying to select "MEDIUM" or "HIGH" from the keypad or remote control has no effect. In fact, the Remote Control unit doesn't seem to function at all. (and yes, I did check the batteries ;->)

Here is the information on the name plate:

LASKO E20739 Blower Fan

Type TFB

CS6082065177

120 VAC, 60 hz, 1.0 Amp

Model: 4920

I reached out to Lasko's online customer support and received the following reply:

"Thank you for your inquiry. Unfortunately, Encompass has no Service Parts or Literature available for your model. We apologize for any inconvenience".

Does anyone out there have any ideas about how to troubleshoot & fix this item? THANKS!