Teardown and RE of a cheap OCXO

[wan hung lo]

Hello folks,
I decided to open the can of a cheap OCXO marked OSC5A2B02.
I must admit I am quite puzzled with the circuit. Is the "501" IC a micro, or ASIC? I think it is something programmable, because the controll loop of heater transistor seems like good PID. But I am puzzled by the oscillator circuit between pin 6 and 14 almost as much as that strange LLC thingy connected to pin 15 and 16. And why the 4V (reference?) is connected to two pins of the IC?
The output to the base of the power transistor is purely analog, no PWM, so if it is a micro, it must have an DAC able to source a couple of milliamps.
Any opinion will be welcome.
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[Doctorandus_P]

Apparently you've already spend some time reverse-engineering the circuit.
So start by drawing a decent schematic from that circuit, and then post the schematic.

Quad opamps usually have 14 pins instead of 16, so it's probably not a quad-opamp.

While reverse engineering, you should start by verifying continuity between the power input and the power of that IC (Apparently Freescale makes some P1011 "Communications processor" but that is probably not it)

Probing a picture with a DMM for continuity is unlikely to give satisfactory result.
So do the basic work, draw a schematic and post that.

[magic]

Do they sense temperature with a thermistor hanging off of the 5V supply or is there more to it?

[wan hung lo]

Here is the schematics I've made. Unfortunately it does not make me any wiser. I can only identify the oscillator output pin, ADC in and DAC out. Maybe somebody have a clue?

[wan hung lo]

@magic: I was confused too at first No, they read the thermistor from the other terminal - from the voltage divider via pin 11, see the schematics above.

[Smile2016]

Have you had any luck reverse engineering this 10MHz OCXO? My heater broke, so I opened mine up and compared it to your schematic. I've attached an image showing the differences. It seems like the 501 chip is a simple custom IC with just a few basic components inside. I’ve identified an NPN transistor with biasing resistors around the oscillator and an operational amplifier on the temperature compensation side. I can create a schematic if anyone is interested. My goal is to repurpose the entire setup for a 40MHz OCXO that I need for some experiments.