After a failure on my lab´s A/C, I`ve found out that my Rigol DM3068 doesn´t like high temperatures. If the temperature is below 23 degrees celsius, It works ok (passes the auto test). Above this temp it becomes intermitent with displayed measurement out of range and relay banging (in any mode : resistence, voltage or current). Also, the NPLC indicator doesn´t advance continuously, but stop many times like as the microprocessor responsible for measurement is overloaded. If the temperature is above 30 degrees celsius, the boot takes forever to end (more than 10 minutes) or maybe it just locked up.
I opened the case in hope of something obvious, but nothing jumped to my eyes. (yes, i put my finger on all heat sinks and big ICs searching for something overheating)
There is one funny thing, if the temperature is high, like 31 degrees, even after allowing the meter to cool to the ambient temperature, it fails imediately during power up. I mean funny because if there is something overheating it should require some time to fail...
I don´t know if the problem is present since purchase, because I never faced it before A/C failure and the warranty is already expired. I contacted the rigol distribuitor (I purchased from them) and they say that ANY problem besides recalibration is beyond economical repair. So, try to repair it by myself is my last resort. Does anyone has an schematic of DM3068 ? I will apreciate any help.