HP8590L A4 mixer module insides

[Bjoern]

Does anybody know what these C2 components are ?
I expected to find two diodes inside the mixer but only found capacitors and resistors ?!
There are no components under the soft grey pads.

[RFMWdude]

They are just what you would expect here: Mixer diodes. To be precise: Avago (now Broadcom) HSMS‑2822.

Datasheet:
https://docs.broadcom.com/docs/AV02-1320EN

[Bjoern]

Thanks for the TIP !!
I measured them and they actually work

Back to the drawing board.

Would you have an idea why my SPAN below 100khz might not work but above its ok ??

[Bjoern]

Can I ask you:

i see some spikes of my calibration signal on the screen.
When I disconnect the YIG from the A4 mixer the spikes on the screen disappear.
Can I conclude from that, that the YIG is working or can there still be issues with the YIG causing amplitude issues ?

[Bjoern]

Today I did some more measurements on the YIG supply buy adding resistors in series of the main coil and the FM coil to measure the current (by measuring the voltage over the resistors).
I believe the signals for both coils are OK which rules out errors on the analogue board.

Since I am unable (due to my instruments) to measure the output of the YIG or any mixer in the gigaherz range I am still not sure if the output of the YIG is too low, causing low signals further down the signal path.

I connected a 10Mhz sine wave signal with 1.2 RMS volt to the SA but the SA shows only several millivolt on the screen. Somewhere the signal gets depreciated.
How canI find where the signal decreases without being able to measure the 2.12 Ghz ??