GaAs FET Troubleshooting: Assembly Not Working

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The assembly of the GaAs FETs in the HF system stopped functioning despite correct voltage readings at the drains and sources. Users suggest that potential issues could include a shorted inductor, open capacitor, or faulty solder joints and connectors. There is a request for a schematic to better diagnose the problem, as well as inquiries about the output load and power levels being used. The discussion emphasizes the importance of understanding the circuit configuration to identify the root cause of the failure. Overall, further details and schematics are needed for effective troubleshooting.
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Hello. I use 2 GaAs fet in a HF system. This assembly worked properly for several weeks and now doesn't work anymore. Before replacing these 2 transistors I would like to know how it is possible that all voltages ( drains & sources) are still correct, while the complete assembly stopped to work ?
 
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Can you post a schematic? Are they in the output that drives a 50 Ohm load? How much power were you pushing out to the load? Was the load ever disconnected?
 
Last transistor drives 680R and power "extracted" from this stage is probably les than µW. My question is why voltages are still the same as when this assembly was Ok.
 
I think we really need at least a partial schematic and part numbers to help you. Otherwise we would just be guessing.
 
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Well, a shorted inductor or open capacitor come to mind; and of course a faulty solder joint, cable or cable connector.
Just the usual suspects.
 

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