If you are experiencing trouble with your SR810 or SR830 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.
SR810 & SR830 Troubleshooting Guide
Symptom 1 — Front-panel red overload LED is constantly lit
Most likely the front-end transistors and op-amp of your lock-in amplifier are damaged. If you look in the CURRENT & PREAMPLIFIER page of the schematics (located in the back of the user manual) you will see that the first active components in the voltage input signal path (U102 and U108) are NPD5564 FETs from National Semiconductor. This part became obsolete several years ago. Since then, we have used several replacement parts in our lock-ins. To determine which replacement parts you need, you will have to inspect your instrument and find out what part is currently being used.
Start by unplugging your instrument from the AC line. Then remove the top and bottom covers. Looking down from the top of your lock-in, you will see a large aluminum shielded area that covers the width of your instrument. Remove the four top screws and the two bottom screws and slide the shield off. Two printed circuit boards (PCB) are now visible. Remove the bottom PCB and unplug the ribbon cable which attaches to it. Remove the small aluminum shield on the PCB.
Locate U102 and U108. These are the components that need replacing. They may be in an 8-pin DIP socket (pins in straight lines), or they may be in an 8-pin CAN socket (pins in a circle). If they are in an 8-pin DIP-socket, you'll be replacing each of them with an LSK-ASSY assembly. If they are in an 8-pin CAN socket, you'll be replacing each of them with an LSK389B.
You should also replace the current input op-amp. Locate U101. Replace this component with an LT1793.
You can order the three replacement parts you need by clicking here.
If you are still having trouble your SR810 or SR830, your instrument will need to come back to SRS for service. Click here to get an RMA number.