I'm awaiting official instruction on the channel 2 repair. I guess I got the go ahead to remove the void warranty sticker! At any rate, Nixxon had suggested doing the self-cal which for some reason I never considered. I had a set of images on the decades of channel 1 and 2 performance while triggering on the sync out signal locked to channel 1. The self-cal without a doubt has greatly improved the higher frequency performance. The low frequency is still riddled with glitches BUT... the glitches are now occurring in a more regular (less random fashion) and aligning on the trace. Just a note, that on my unit the Channel 1 to Channel 2 phase error at 100Hz can be as large as 18 microseconds!!! Crazy!!!! It's like they're not even on the same clock and it seems totally random. I sure hope these resistors magically address all these issues.
As for the repair, I need to go and buy some 0603 resistors to modify the circuit. I only have 1206 and 0805 in my parts bin now. I sure hope I get compensated for all this diagnostic and debug work for the Siglent.
Teardown pictures to come. I know some people wanted to see all the parts and it doesn't look like any of mine have been sanded down.
P.S. If anyone is wondering why I don't test the 10MHz range, it's because the output sync signal can only go upto 2MHz for some reason???
Just a note, that on my unit the Channel 1 to Channel 2 phase error at 100Hz can be as large as 18 microseconds!!! Crazy!!!! It's like they're not even on the same clock and it seems totally random. I sure hope these resistors magically address all these issues.
Yeah, RF-loop, I have to say, you're amazingly knowledgeable and familiar with this system. If I didn't know any better, I would say you were a consultant! So it would seem that you're describing a square wave formed from comparator filtering of a sine wave--thus amplifying any error in the sine generation. I wonder why they chose the square wave to be generated like this instead of DDS. So at least pulse mode allows the DDS generation of the signal but unfortunately, that is limited to 5MHz in stead of 20.
I too noticed the very short and low sync pulse which is not aligned to the edge of the actual square wave... but that now makes sense based on how rf-loop described the generation of the square wave. That must be the trigger point for the ADCMP562. I also agree with nixxon that the unit has some pretty nice high spec parts inside. I found mine has exclusively Rubycon 105°C Aluminium caps inside which quite nice. I feel a little bit of firmware work could really take this generator to the next level. I should probably talk to them some more but I need to buy some resistors to get this repair job done first.
I activated "SelfAdjust" and now the DC output is exactly 1 mV more off than before.
There has to be a correct way to perform this "SelfAdjust" procedure...
I wonder what will happen if both channels are shorted to ground while doing it? As I do it, I will measure current between signal and ground as I "SelfAdjust"...
EDIT: With DMM in mA/A mode connected between CH1 signal and GND, nothing was registered on my DMM (Fluke 87) while "SelfAdjusingt" the SD1020.
Does anybody know how many mA the DC output of the SDG1000 series can handle?
And how does the unit handle a short?
I guess it is not supposed to be used as a PSU.
I have noticed that the sync signal is a pretty short pulse (manual: ">50ns") that is occuring somewhere during an arbitrary waveform. I do not recall where it occurs during a built in wavfeorm.