Repair of dead channel on Rigol DG1022

[thomaspfenning]

Here is my experience.  For some reason my dg1022 ch1 died after using one time. I was able to use ch2.  Then decided to see if I could fix ch1 after realizing I was beyond the warranty period.  First thing to check was whether schematic and parts were available. No way, since the soic-8 ic used for the output had the numbers ground off. How thoughtful of them Chinese.  But being used to these shenanigans , I mapped out the pin connections and measured voltages on the good and bad channels. From this I deduced that they were just using a high performance op amp.  Went to the digikey op amp selector and filtered out all chips that would not work. ended up with only a couple choices. The THS4631D met the criteria and I installed. Yea, it worked.  Only problem was I got the version without the thermal pad. I put high performance thermal paste on the bottom of the chip and added a large aluminum heat sink on the top .   To test I ran ch1 at 5v  with 1 Mhz square ware into 50 ohm to thermal equilibrium, and cycled a few times.
The square wave was almost ideal and only dropped 50% when going from no load to 50 ohm which is correct.  If you try this fix please let me know.

Thomas Pfenning