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SR860 & SR865A Tech Support

If you are experiencing trouble with your SR860 or SR865A you can either send your instrument back to SRS for service, or you can try and fix the problem yourself. If you wish to send the instrument back now click here.

If you wish to try and fix the problem yourself, the following troubleshooting guide may help you.

SR860 & SR865A Troubleshooting Guide

Symptom 1 — Front-panel red overload LED is constantly lit

The input voltage preamplifier uses a low-noise matched JFET (LSK389B), 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.

For a detailed set of instructions on replacing the front-end JFET click here.

You can order the three replacement parts you need by clicking here.

Upgrade firmware in the field

Click here to download the firmware upgrade procedure.

If you are still having trouble your SR860 or SR865A, your instrument will need to come back to SRS for service. Click here to get an RMA number.

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