I think, in these now showed test results there is not used any these modifications. If there is, then some capacitor is broken. With these modifications can not get these results what I see now there in signal pictures.
Unfortunately, I have to stop my experiments for a while. I have some exams in the next two weeks for which I need to prepare and fixing the noise is currently draining too much of my resources.
I think, in these now showed test results there is not used any these modifications. If there is, then some capacitor is broken. With these modifications can not get these results what I see now there in signal pictures.rf-loop,
These are test results with the new Owon PSU. Everything works OK as long as there is nothing connected to pin 5, the bad duty cycle captures are with a probe or a 2" wire attached to pin 5 which acts as an antenna. Of course, I don't think it should be so sensitive, but it works OK as long as you don't attach anything extra to it. I suspect that the Owon engineer used resistors with too high a value for the voltage divider, probably to try to prevent power losses. Maybe lower value resistors with the same ratio would make this pin less sensitive.
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The main challenge was dealing with the signal references, Q1 is in the primary side and is referenced to GND-A, D8 is in the secondary side and is referenced to GND-B. Note that connecting a ground lead to GND-A would cause a short circuit and as a minimum will blow the fuse, so that is out of the question. Connecting a ground lead to GND-B is not a good idea either, it probably wouldn't be catastrophic, but it will short out the CC current sense resistors (R14/R14A/R14B). So the only option is using GND-C which is also Chassis gnd. GND-C is separated from GND-B by no more than 125mV, so it's a fair reference for D8. However, it's a different story for Q1, because GND-A is nearly the same as GND-C half the time, but separated from it by 100s of volts the other half, it depends where on the mains AC cycle you are at. However, this knowledge is helpful, because you can focus on just the waveforms during the time that GND-A is nearly the same as GND-C and ignore the rest. Just use, for example, single trigger, until you capture something with the correct baseline.
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btw, what is this newest PSU version number?
TomC, you done very well documentation but I have confused a little.
Because I remember the blow of R7731 that I had before. I had the ground clip (multimeter) to Z-plate ... (230Vac).
From what I read the GND-A and GND-C is almost identical (they are connected to Z-plate together) but it is better to use only the GND-C or Z-plate.
Please, where was the probe ground clip at your measurement on Q1 and where was at the D8?
Note= the AOZ1094 has received and everything is OK.
About flyback freq. Did you note any Vdd variations related to AC powerline variations?
(R7731 freq is some amount sensitive for Vdd (and of course also temp) specially under 15V)
btw, what is this newest PSU version number?
Today I only had time to measure the VDD pin of the R7731A with different mains voltages. The easiest way to do this is with a voltmeter, the ground probe on GND-A (Q1's heatsink), and the red probe on the cathode of D6 (which is connected to the VDD pin). Fortunately this time there were no surprises. The results were as follows:
100VAC mains --- 16.58VDC
140VAC mains --- 16.66VDC
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Also, I have done a measurement to R7731N (socket dip-8) on PCB-T115-J Rev6 with 230Vac mains (50Hz) and the Vdd was 18.09Vdc after a half an hour of operation. Starts cold with 18.5 almost and slowly stabilized to 18.09Vdc
TomC, with my pleasure but confirmed please the connections to my attachment photo.
OK, TomC take your time that you are needing and I am here to measure whatever you want.
I prepare a work about AZ1094 circuit...it has a lot of interesting!
Following photo shows how this joined effects the output noise to 5.6V path. Very well, 41.6mV from 93.6mV only with better ground plane, closely to 36.8mV ref. measurement.
The second wave (yellow) is the gnd-noise, both of tip and gnd grip on Z-plate.
(it continues...)
OK, TomC take your time that you are needing and I am here to measure whatever you want.
I prepare a work about AZ1094 circuit...it has a lot of interesting!That'll be interesting!
Your PSU board is different from mine, so I attached images of where I think it'll be easiest to hook up the probes. CH1 should be on D8's anode, and CH2 on Q1's drain. Both ground leads to the Z-plate. Make sure the probes are set to X10 because the peak voltage at Q1's drain may be more than 400V with 230VAC mains. While the scope is running you'll see an image like #1, jumping up and down. When the baseline of the CH2 trace is level with the ground marker it is as closely referenced to the Z-plate ground as you can get. To get a capture like #2 I used single trigger. Sometimes the baseline will be at the correct place, so when this happens I capture the image.
Following photo shows how this joined effects the output noise to 5.6V path. Very well, 41.6mV from 93.6mV only with better ground plane, closely to 36.8mV ref. measurement.
The second wave (yellow) is the gnd-noise, both of tip and gnd grip on Z-plate.
(it continues...)Very interesting!
I'm wondering why you are using 20mV/Div (restricts bandwidth to 20MHz), are the signals too small if you use 50mV/Div?