My DS1104Z (bought some month ago at Batronix, calibratetd before testing, Firmware 00.04.01.SP2, Board Rev. 0.1.1) shows the AC-Trigger issue, but doesen´t show the 5µs Delay-Jitter, tested with different frequencies (Signal source: Siglent SGD1025, connected directly with BNC-BNC coax-cable). The AC-Trigger is only relevant for freqencies higher than 1 MHz and gets worst with shorter horizontal settings as expected. LPF reduces the jitter, averaging supresses it perfectly.
Also by moving the AC-Trigger Point upwards to the maximum level of the signal on the screen, just before trigger gets lost (for example the top of the overshoot of a square wave) I can eliminate the jitter entirely. This indeed is a behavior I that is common on my older analogue scope (Philips PM 3055), there I often have to adjust the trigger level to achieve a stable picture. With trigger set to DC the test-signals will always be stable on my DS1104Z.
Frequency Counter works allways correct.
The AC-Triggering-issue obviously semms to be a common problem spread over different Rigol-scope-models, but the delay-issue seems not to be common. If my observation is correct, concerning the DS1kZ-Series, all of the DS1054Z mentioned in this thread show this issue, but only few to none DS1074Z and DS1104Z (like mine).
This lets me raise a theory: Could this issue be caused by spreading of specs of some parts on the boards? Therewith I mean, that when Rigol does a final testing of the boards as quality check at the end of the manufactoring process there maybe some boards rejected due to not reaching the specs to a margin of lets say 100%. But imagine (most of these) these boards are not defect, but only not good enough to be sold as 70 or 100 MHz boards. If there was a appreciable number of rejected but not defective boards maybe Rigol decided to sell them as 50 Mhz boards, the DS1054Z.
They will work up to this frequency but will not be accurate enough to met the specs of his predecessors. Who of the normal users of the DS1054Z can really carry out measurements of this precision to find out these certainly only very small differences - and from a practical view they would certainly never matter in normal use. It matters only Rigol to classify the different models.
BUT could this theory explain this observed phenomenon?
What will say the experts here in this forum whose knowledge i really admire?