Products > Test Equipment
Conversion of 500MHz TDS744A to 1GHz TDS784A
44kgk1lkf6u:
To be clear, the external attenuation setting was 1x in all the measurments.
I just got out a 20 dB attenuator and measured the bandwidth at larger amplification. From 100 mV / div down to 10 mV / div, the edges are 355 ps. At 5 mV / div, it is 400 ps. I don't have an attenuator that makes the curve fit on the screen at 2 mV / div.
Table 1-16 in the service manual lists the rise time for the 580D and 784D as 400 ps at 10 mV / div to 1 V / div and 530 ps at 5 mV / div. So maybe the bandwidth is even higher from 200 mV / div to 1 V / div, but they did not want to guarantee it.
Tantratron:
--- Quote from: 44kgk1lkf6u on February 05, 2024, 05:54:54 am ---To be clear, the external attenuation setting was 1x in all the measurments.
I just got out a 20 dB attenuator and measured the bandwidth at larger amplification. From 100 mV / div down to 10 mV / div, the edges are 355 ps. At 5 mV / div, it is 400 ps. I don't have an attenuator that makes the curve fit on the screen at 2 mV / div.
Table 1-16 in the service manual lists the rise time for the 580D and 784D as 400 ps at 10 mV / div to 1 V / div and 530 ps at 5 mV / div. So maybe the bandwidth is even higher from 200 mV / div to 1 V / div, but they did not want to guarantee it.
--- End quote ---
Sometimes it is strange with these acquisition board.
Two years ago, I've purchased a TDS784C from eBay but when I open to check, to clean the all unit then I saw the 4 capacitors so I was not happy after the Belgium seller (the 4 cap should not be there for 1 GHz). However I connected on each channel my Leo Bodnar pulser and to my surprise, the bandwidth was really as a TDS784C.
Go figure out... tekronix left the 4 capacitors normally found if TDS754C but declared as TDS784C
Rafiki:
I've made the conversion too. Removing the jumper resistor and the four 3p3 caps and I get the attached slew rate with a real world signal and 1GHz probes. The upper trace CH2 is with TEK P6243. The lower one, CH3, looks very very similar when switched to the same vertical resolution but is taken with an R&S ZD10 via adapter. I know the same signal with same ZD10 on another 4GHz scope shows a slew rate of about 300ps instead the 500ps here on the TDS744/784. So the limit here is the scope. Anyway I think this is quite good for this old beast.
Measuring with an HF generator shows that my TDS744/784 just reaches the 1GHz. CH2 has a bit less than 3dB attenuation at 1GHz while the others do have slightly over 3dB / 1GHz. Didn't note the values before upgrade though.
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