Hello everyone, I bought a defective spectrum analyzer, can someone help me with a service manual for this model or something similar or close. I can't find any documentation and I don't know where to start. At first glance, I saw that a relay on the attenuation side was missing. I skipped, injecting signal on low pass filter, about 50mV sine 60 Mhz, but nothing happens. I replaced 2 BFP420 type transistors but the same. I don't know the steps I have to follow. I am attaching some photos below. thank you