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| Hantek 2000 series - 2C42/2C72/2D42/2D72 |
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| mostorer:
Hi Microcheap, the FW version is the one you posted to permit calibartion, as the current FW version does not permit AWG calibration. FPGA version is the last one, so 04. About coaxial cable, I was wondering if using the normal probe wasn't enough at least to see calibration process running. Then, of course, to have the right calibration the coax cable is important. If you could confirm me the FW and FPGA release (including the upside down screen), I could try newly using the suggested resistor values. I would do that as I have a little concern about waveforms amplitude. I was supposing that, setting a sine wave with Amp at 2.5V I would have on the scope a wave with 2.5V p-p, while on the manual I have just seen within the example that the p-p value showed on the screen is 5V, so the amplitude should only be related to a semi-wave. ??? Thank you in advance for your patience. |
| gf:
--- Quote from: mostorer on April 07, 2020, 10:01:35 am ---I was supposing that, setting a sine wave with Amp at 2.5V I would have on the scope a wave with 2.5V p-p, while on the manual I have just seen within the example that the p-p value showed on the screen is 5V, so the amplitude should only be related to a semi-wave. ??? --- End quote --- Unless explicity stated, it is IMO never perfectly clear wheter "amplitude" is supposed to mean peak-peak or semi-wave (or even something else). Yet another difference makes the terminatinion impedance. With no load you get 2.5V semi-wave, but when you terminate the output with 50 Ohm, you'll indeed see your expected 2.5Vpp, due to the 50 Ohm output impedance of the AWG. It all depends... --- Quote from: mostorer on April 05, 2020, 06:32:52 pm ---... Found that the 150ohm resistor at pin 2 of EL5166 was in short circuit, so changed with a new one. After that the things were better, but not exactly as expected. I checked the outputs from DAC and levels were ok, so I decided to change the feedback resistor on the output opamp. From 560 to 186 ... --- End quote --- That's odd. If things are off by say 10..20%, then it is still plausible, but factor 3 isn't. Is everything related to the AWG populated as in a geniune 2D72? Are the various 0 Ohm resistors replaced with the actual values as well? Are the 49.9 Ohm (68X) resistors from the DAC outputs to GND present? What DC voltage do you measure from DAC pin 17 to GND, and from pin 18 to GND? What is the value of your Rset resistor, from DAC pin 18 to GND? When you set the AWG to rectangle with amplitude=2.5V and offset=0V, what peak-to-peak voltages do you measure on the two DAC outputs? Expected are about 500mVpp on one output, and about 850mVpp on the other one. EDIT: I have added photos of a genuie 2D72. Regards, gf |
| mostorer:
Thank you so much gf. Next days I will find the time to newly open my 2c42, check all resistors value (they should be ok, as I followed instructions found on this thread and double checked with published images), measure all pins value and report back on this thread. At the same time I will try to find a bnc-bnc cable to comlete the job. I was quite sure to have one but not able to find it now and, given the current situation, not sure to be able to find one quickly. Regards. |
| gf:
--- Quote from: mostorer ---...so I decided to change the feedback resistor on the output opamp. From 560 to 186... --- End quote --- Btw, did you change only one resistor here? Note that U13 is supposed to act as differential amplifier with symmetrical feedback network, in order to eliminate common mode gain/bias. Making it asymmetric defeats this goal. See https://en.wikipedia.org/wiki/Differential_amplifier#Symmetrical_feedback_network_eliminates_common-mode_gain_and_common-mode_bias gf |
| mostorer:
Yes, you are right but, to be a simmetrical diff amplifier as I also supposed (as also suggested on ADC902E datasheet) I should have to find a resistor from U13.3 to gnd. Not being able to find it. Also all resistors I have are exactly as in your picture, so if there is one (as it should), it was already the right one. mostorer |
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