I bought a Sunbeam heating pad. It has low/med/high settings, and turns off after two hours.
The back of the controller says ‘Sunbeam SLA103′.
I wanted to eliminate the shutoff, I’m using it to heat my fermentation bucket.
I found good information in this instructable, Disabling Auto-Off on a Sunbeam Health at Home heating pad.
I opened the controller up, and the circuit board was similar, but some of the components had moved, and the microcontroller was different.
Microcontroller is a NXP Semiconductors HEF4060BF. I figured this is similar to the CD4060, and found this datasheet, 74HC4060D Philips/NXP.
Looking at the circuit board, there is a capacitor (C3, 480nF) between pins 12 and 16 which makes sense if pin 12 is the master reset. Pin 3, Q13, is connected to the triac (T1). Pins 9 and 19 have a capacitor (C2) and resistor (R7), and this likely makes up the RC timing circuit. So this chip is a 4060.
As you can see on the circuit board, I removed C3. I replaced it with a 10K ohm resistor, and now the heating pad stays on indefinitely.