Well I already tried with capacitor replacement and it didn't help. It's not a too great problem for me to replace the IC, if it's suspect. Coil could be a bigger problem. The closest I can find easily available it 100 µH. From TomC's responses, I came to understand that a lower number should be looked upon as a replacement, but the next lowest I can easily find is 10 µH.
Just thought I could add this info about serial numbers of latest versions: ...............
If you do, it would be very nice if you can post some images of the GND noise test results on your new scope.
As a point of interest, I wonder if the serial number is based on the Chinese calendar as far as the week of the year is concerned. If that was the case, week 19 would correspond to June 16-22 on our calendar. Again, maybe it's just a coincidence.
Actually I chickened out and have ordered the Rigol 2072.
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As a point of interest, I wonder if the serial number is based on the Chinese calendar as far as the week of the year is concerned. If that was the case, week 19 would correspond to June 16-22 on our calendar. Again, maybe it's just a coincidence.
From what I saw, the 1st of 2013 was 10 February for China. For example for the serial SDS71021319652 the 19th week is almost at the end of June. But I am afraid that the week in China isn't 7 days period allways...
As a point of interest, I wonder if the serial number is based on the Chinese calendar as far as the week of the year is concerned. If that was the case, week 19 would correspond to June 16-22 on our calendar. Again, maybe it's just a coincidence.
Just thought I could add this info about serial numbers of latest versions:
I mailed the supplier on ebay to check I would get a late low noise version and got this reply:
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I am sorry but I think this is mistake on EEBLVD, I just checked with manufacturer, our serial # is 1319XXX, it is new version as well ( please e-mail to sales01@owon.com.cn to verify what I am saying if you doubt that ) , 19 not means 19 weeks ( we doubled checked with manufacturer) we warranty you get 2013 June low-noise version ( you can check with manufacturer for the serial # ), for example the serial# SDS71021319652 or later version.
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First sidenote: I have 1303xxx in stock and just as arrived from factory.
For those who know my story, I got full refund from my dealer after I returned the scope to Owon. My dealer didn't refund the customs charge and tax, but they sent me an equal value gift.
Actually I chickened out and have ordered the Rigol 2072.
For those who know my story, I got full refund from my dealer after I returned the scope to Owon. My dealer didn't refund the customs charge and tax, but they sent me an equal value gift.Glad to hear that!
Did you buy a different scope or are you still looking?
Well I already tried with capacitor replacement and it didn't help. It's not a too great problem for me to replace the IC, if it's suspect. Coil could be a bigger problem. The closest I can find easily available it 100 µH. From TomC's responses, I came to understand that a lower number should be looked upon as a replacement, but the next lowest I can easily find is 10 µH.AndrejaKo, I think it is possible that you are having trouble with the current sense ending the cycle prematurely, can you check the value of R40, if it's too high I think it could cause a problem similar to this. R40 is the current sense resistor and when the voltage across it reaches 330mV it ends the cycle.
First sidenote: I have 1303xxx in stock and just as arrived from factory.
Probably a factory refurbished scope.
I just checked the value using 4-wire measurement system and I got the expected value. My result is 0.269 ohm. I measured directly from one end of the lead to the other end of the lead. It remains stable over time.
The half-level points are still there with an ON Semi MC 34063A, but are now a bit different. Now every square starts with at least one pause near the mid level. Sometimes, there are more of those pauses. The difference is that they are usually very, very short, only few tens of nanoseconds in length. There are several types of bad ones, though.
The most common type of square wave is the fast 2 level one. After probing for a while, I'd say that they're more than 90% of captured squares. The is some variation of time it takes to jump from the first voltage level to the second, but it's usually very short.
There are also two more types of square waves I've seen. There's the fast 3 level one. First level dwell time of always very short. There's also a 2 level slow square. It seems to be a bit more common than the 3 level one, but it's still quite rare.
Hi TomC!
I forgot to show the general duty cycle and to write about the large peaks in the last post, so I updated it. Basically, the peaks are still there and they don't seem to be related to MC's operation. Could the TL431 be producing them somehow? Duty-cycle is close to rf-loop's.
Unfortunately, I haven't functional my scope. Pehaps some measurement to my circuit will help you.
Still, I am wait the AOZ1094 to arrived.
Carrington, the EMI shielding where you thinking to apply? Front or back of the screen and what dimensions we are need?
I'm not sure I understand what you're saying...
Do you want me to try to run the DAC board by using only an external power supply?
Right now, I only have one good linear "lab" power supply, with only one channel, so it will take me a while to make a PSU for -7.6 V and then to rig everything up so that it starts.
I was thinking about doing things the other way around and start by running the PSU with a dummy load and then probe with another scope (when I manage to arrange access to it), since that to me seems easier to do. I'm pretty sure that the noise source is in the PSU itself. Few pages ago, I tried out the PSU with adapter power cable disconnected and probed the -7.6 V with my soundcard. I still had the noise peaks with same frequency as the ones I'm seeing on the scope GND.