Rigol DSA815 - Page 1
Forum section: electronics / repair

author: G3ROO
author_rank: Newbie
timestamp: January 22, 2021, 12:25:29 pm
content: My 815 noise floor is up by 17db.... I knew when I did it working on a valve receiver!I need physical help!! I have developed central blindness in my right eye and with only one eye working it is extremely difficult to place things on pcb ! Does anyone know of a service engineer for the Rigol 815... I have google without successI have opened it and microscope inspection found that U504 had been replaced (obviously on test prior to dispatch) and this proved to be the cause of an intermittency that I noticed occasionally in useCan anyone help please?Ian G3ROO

author: CJay
author_rank: Super Contributor
timestamp: January 22, 2021, 12:42:23 pm
content: If you're who I think you are, you're local to me Ian?IO83TJHappy to help.

author: ted572
author_rank: Frequent Contributor
timestamp: January 24, 2021, 12:47:46 am
content: Hello Ian and CJay:You may be interested in this EEVblog link to 'Rigol DSA-815 repair':https://www.eevblog.com/forum/repair/rigol-dsa-815-repair/msg907034/#msg907034Also see the PDF attachment below:This may provide some ideas, help, or at least some encouragement. Good Luck, Ted1. Are you sure U504 is intermittent? If so, it is certainly one of the easiest devices to replace. Although of course I wouldn't expect this device to bethe cause ofrelatedto your higher displayed noise floor.2. You are going to have to remove the RF Section's Top Machined Aluminum Shield Plate. Please note that there are two different lengths of screws used here. You willneed to mark on the Shield Plate where the longer screws had been used. After you remove the RF section's Top Machined Aluminum Shield Plate you should fabricate, or acquire aluminum standoff spacers that are the same height as the Shield Plate.Note: If you have access to short metric screws you won't have to deal with using standoffs with the longer original screws, but it is complicated by requiring two lengths of shorter screws. I think using the standoff makes the job much simpler.Then leaving the Top Shield Plate OFF - screw the PCB's RF section secure to be sure that this area makes good contact with the bottom side shield compartments. Be sure to use all the longer screws, and at least 90% of the shorter screws evenly distributed. Now you will be able to power up the DSA815 and probe through the RFfront-endsection starting at the SA RF Input to see where you are having the additional RF loss that is causing the elevated noise floor. You can easily use a Low Level RF Voltmeter (e.g Boonton RF MilliVoltmeter, etc), and inject a 20 MHz, 10 mV (adjust the Leval as required) signal into the SA Input. The damaged component(s) should be limited to being between the SA's RF Input and the First Mixer. So essentially all your measurements will be at 20 MHz (or whatever source test frequency you choose to use).The impedance's here are all low (50 ohm) making it easy to compare and appreciate the various RF level differences through the front-end stages.This may initially sound complicated, but you will see that it is all easy to do if you have basic experience with SMD/SMT components/PCB layouts and RF/MW circuitry.Note: Differences in replacement RF component device gain/loss from the original components will be compensated for by the SA's built-in Calibration routine. So you shouldn't have to worry about having to get a 'Rigol factory re-calibration' done on your SA.Note: The current edits made here are inbold italics.If you have questions please feel free to ask.

author: ted572
author_rank: Frequent Contributor
timestamp: January 26, 2021, 12:26:21 pm
content: Hello Ian and CJay:I made a few edits in my post to you above to try to give you additional confidence that you should be able to fix your DSA815 SA.Please note the the DSA RF input blocking capacitor is only ratted at 50 VDC. So please be sure to check it out also.If you were actually probing around inside a valve type receiver with your DSA815 you may have a big job a head of you, although it should be doable.

author: jc101
author_rank: Frequent Contributor
timestamp: January 26, 2021, 07:39:52 pm
content: I have a DSA815-TG with the EMC option that will eventually go up on the Buy/Sell section, should there be issues with repairing yours.