Hi edpalmer,
The FRK is - or was - my labs time reference. I do have a GPDSO ordered from China as i was thinking along those lines, but it hasn't arrived yet. According to my Siglent 1202X-E, the OCXO Frequency stays exactly at 10MHz during the sweep. But: it does not have enough digits to show a 15Hz difference anyway I haven't measured with my frequency counter, as it normally takes the FRK as external reference. But i will try to see if i can see the OCXO sweep, even if the absolute value is wrong, so thanks for that tip.
For now i have measured the lamp temperature only. What i did was press a PT1000 against the metal casing of the lamp, basically covering the lamp inspection hole and pressing it place with the detachable lamp cover and some foam. The temperature, according to the HMC8012 that the sensor connects to, stops at 88,4 C. However this is a 2-wire measurement, the real value must be lower The FLIR camera pointed at the heater tranny shows just under 100. I did not measure directly on the glass, as the opening is only around 2,5mm and i've no probe that fits. I don't trust either measurement, my gut feeling tells me they are both lower than reality. Have to order a smaller PT100 that fits on the tab of the TO-220 heater tranny, the one i use is way to large, even to strap it to the lamp housing closer to the heater.
I did not measure the resonance chamber and OCXO temperature yet. They both are heating and since the unit worked before, I see no reason why the broken trace of the lamp heater could have offset them, so for now i went at the servo board.
I'm reluctant to mess with the physics package until i have ruled out anything on the boards, but of course you are right to point that out.
If the servo board turns out to be okay, i'm going to do a full alignment of temperatures and OCXO i guess.
Another problem i encountered is, that the service manual does not list the part number for the temperature sensors. Only parts mounted on PCB are listed, but the sensor is inside the lamp unit. So i can't tell if they are off. My unit also has no potmeter for lamp temperature. There is a fixed resistor mounted where the pot should be, which seems to be selected at test like many other resistors.