Siglent SDG1005 AWG output level error - Page 1
Forum section: electronics / testgear

author: commongrounder
author_rank: Frequent Contributor
timestamp: October 29, 2021, 07:52:01 pm
content: So, I’ve owned this SDG1005 unit for a long time. It’s main use has been for audio frequency work. Every so often I run the self-adjust routine without incident. However, this last time there was a problem afterwards. I’ve been using this unit with a Siglent scope to run Bode plots. The drive level I programmed in did not match with the expected measured signal level on the plot. I ran some tests on the generator and found that the output (on both channels) does not always match the display. At higher output levels it’s low. This is measured in high-z mode, with no load but the AC voltmeter (Tektronix DMM4050). The tracking error is a linear one, which I was able to plot. Up to 707.1mv, the output tracks within a couple of percent. Acceptable. But at a displayed 707.11mvRMS (2vp-p), a relay range switch takes place, the measured output decreases, then continues at 74.4% lower than indicated output up to the maximum. As I said above, BOTH channels exhibit this same problem. I have to assume that somehow a register in the unit became corrupt during the self-adjust. Has anyone else experienced this? I have replaced the unit, but I’m wondering if it’s worth sending in to be checked. Maybe recalibrating it would clear the issue, or not…

author: tautech
author_rank: Super Contributor
timestamp: October 30, 2021, 07:26:29 am
content: Maybe the Performance Verification Test section in the Service manual can help focus in on where the problem lies:https://int.siglent.com/u_file/document/SDG1000%20Service%20Manual_SM02010-E01C.pdfHowever like with any older gear you would be wise to check the PSU is still working to spec.As there are no PSU max ripple specs in the service manual you can use your judgement as to what might be acceptable for the+20 and+6.8 V rails.Although now discontinued there are still limited quantities of SDG1000 replacement mainboards available.

author: commongrounder
author_rank: Frequent Contributor
timestamp: October 30, 2021, 01:01:43 pm
content: Thank you, tautech, for the suggestions. I will look into it further and see if I can uncover anything abnormal. It’s also good to know some mainboards might still be available. Seems a shame to set this unit aside if there is a chance at an economical repair path.

author: commongrounder
author_rank: Frequent Contributor
timestamp: November 05, 2021, 07:56:15 pm
content: Okay. Had some time to dig a little more into this generator. Checked the power supply, and all four voltages are within tolerance, and have acceptably low ripple. I also checked all of the regulator output voltages on the main board, which were spot on. As I mentioned, the lower output levels track normally, but once the range shifts up, there is this consistent 74% output of what’s displayed. This is true for all waveforms and frequencies, on both channels. Repeated self-calibrations affect no change. It does have the latest firmware. I’m wondering; Would running the “feedback channel adjust” routine rewrite the correct data for self-cal, or is this simply a fatal board failure? I suppose I should also see what a replacement main board might cost, to weigh the options. As mentioned, I’ve replaced this unit with the SAG1021i to do the needed Bode plots, which works fine, so there is no time pressure. It would be great to get it running properly, if for no other reason than to be able to pass it on to someone. Thank you for any thoughts from the collective mind.