I read the explanation for the VCO module but I am a bit confused because there are only 2 free connections in my spectrum analyzer in the RF section, and as far as I know the VCO does not hook up to the PC control board (which has a free SMB connector on it), but I really don't think the board is rated to handle any high frequencies. It would seem to support the missing module theory.... I think that the reference oscillator module and the LO summing module were combined in my unit, but there are no free coax connectors on it. Reason for it is that one of my modules has 12 coaxes, and the LO summer has 4 and the reference oscillator has 8 in the pictures for the 7550, so 8+4 = 12, but I need to double check the schematics on it.
I know that the VCO has something to do with YIG because when I search YO92 you get some ebay results for yig voltage controlled oscillators.
30*6 = 180, 15*6 = 90, not even close to the 250 it was getting....
Here is a picture of the fixture:
Top:
http://s14.postimg.org/n9g9vfvjz/DSC_0130.jpgBottom:
http://s18.postimg.org/620noubdj/DSC_0126.jpgThe top (with the lever and the large coaxial screw) is connected to the module by a short piece of hard line into the input section (where the fork in the road is). The coaxial cap (and blown transistor) is in the middle fork of the road, which, if you go according to the diagrams (despite the three paths being identical) is connected to the optional generator module (J5).
The orange wire is connected to the middle two pins of the 10 pin jumper. If I measure the two free ten pin ribbon cables I find that one cable has 0V on those pins with respect to ground (floating) and the other cable has a 5.1 and a floating pin with respect to ground. However the cable which has the 5.1V is kinked in a way that makes me believe it connects to the YIG assy (I found that when the cable is inserted backwards into the YIG it allows the SA to start and does not appear to cause any problems). If I insert the other cable into the YIG (with floats on both middle pins) one way it makes a short and prevents the unit from starting and the other way it makes a sickly noise and appears to hurt the SA so I disconnect power immediately. This causes a IRF540 mosfet to over heat but not get damaged (at least as far as the diode test tells me), It is a candidate for replacement. I smelled the PCB and its defiantly the IRF540 that gave the hot plastic smell.
Considering the kinks in the cable with 5.1V I will assume that it does indeed gointo the YIG assy and that the other cable might be malfunctioning on one end, so I will now attempt to track this cable down.