If you are having problems with your SR810 or SR830 you can call us at (408)744-9040 and speak with an engineer, or email us using our technical support request form. If you wish to send the instrument back to SRS for service click here.

If you wish to try and fix the problem yourself, the user manual may be useful, and the following troubleshooting guide may be helpful too.

Try a power-up reset. Turn the power off, then while holding the SETUP key down, turn the power back on. After two seconds release the SETUP key. If this doesn't correct the problem the instrument will need to come back to SRS for service. Click here to get an RMA number.

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.

Click here to download the input offset and CMMR adjustment  procedures.

Click here to download the Notch filter adjustment  procedure.