Hi,

I was able to remove theYTO from the instrument and test it with the aid of a spectrum analyzer and a few power supplies. Mine needs +20V, -10V, and +5V.



With a coil current of approx. 50mA, I was able to see some oscillation on the spectrum analyzer. YAY!

However, as soon as I installed the YTO back in the instrument, it stopped working.
I found out why: The Main Coil, pin 9, has a connection to ground. As one can see, if pin 9 on the A44 YIG OSC Assembly has a connection to ground, this creates a short circuit and -40V are applied to the main coil. Then, the tuning current is so incredibly high that the YTO won't oscillate.

As soon as I remove the YTO from the instrument, it works fine because with my lab power supplies I have no ground connuection and therefore can properly apply the tuning current.

I wonder now whether it could theoretically be possible, somehow, to open the YTO, find the short circuit and place some isolation tape or so. Has anybody ever done something like that? the YTO microcircuit is definitely fine and oscillates, as it should, but the main coil is somehow connected to the housing, which, according to the schematics, should not be the case I think.


Any ideas?

Best
Tobias