Hi, In the two HP 105B's I recently acquired both had the 10 Mhz 3010A series oscillator which appears to be pin for pin compatible with the HP 10811 series but it has a resistor value listed on the outer case. Trying to research it, the HP 105A/B supplement vaguely said to take a look at the HP 10811 ski. I'm still in the dark about it, so several questions. How good is it compared to the HP 10811? Is it worth the effort as some point to change the outer oven to WarrenS's circuit? There is some mention of using a LM723 regulator circuit.  Is it worthwhile to re-work the PS to one with better regulation? And lastly, Rick K might know the answer to this:  Why didn't HP bring out the 10 MHz as a "new feature" and call it the HP 105A/B Mod II or something? Regards, Perrier