Jeremy & Matt, mine is alive
! Finally I did the substrate interconnection repair (3 of 4) at home and it went well. What I have seen is that there is also an issue with the gold layer. In my case there is a straight connection which gives stress. I did not change the connection (afraid to damage the gold to much) and only re-solder it. I had to touch the gold traces but they did not fall apart. In my case the gold is not as fragile as described by you (maybe improved/newer series). The measured gain of the IF1 is about 0 dB at 2.05 GHz with a slight negative slope. I will measure it at a later moment at work with a real VNA. So, conclusion for my IF1 gain loss of the TR4172:
- Broken PNP of the bias circuit which is replaced by a BC857B
- Three interconnections between the substates were open
When I got this analyser it already had a gain loss of 10 dB and a few weeks ago (did not use it for a long time) no gain at all. I hope that the 10 dB gain loss is also solved now, we will see. Jeremy, thank you for your help and the schematic of the bias circuit, which you already had figured out, was very helpful to me
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Regards, Lex