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© 2016 Stanford Research Systems
JFET Replacement Instructions for
the SR86x Lock-In Amplifier Family
The input voltage preamplifier uses a low-noise matched JFET, Q202, as the front-end
active component. This component is sensitive and may be damaged by overvoltage,
including overvoltage from a static discharge (ESD). There may be situations in which
the user suspects a damaged or destroyed input JFET. Symptoms of a damaged JFET can
be excess noise, or partial or complete signal loss.
The SR86x series lock-in amplifiers are designed to permit the user to replace the input
JFET in the field if needed. The entire process should take about 90 minutes, including
the 60-minute warm-up period needed after replacing the JFET before trimming the
offset voltage.
Materials
To do this, you will need:
1.
Replacement JFET (obtained from SRS)
2.
Phillips head screwdriver
3.
Hex wrenches, imperial size 7/64, and 0.050
