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| Agilent 54835A scope (4 channel 1GHz / 4Gs/s) repair & uphack |
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| Jwalling:
--- Quote from: Converter on November 12, 2017, 12:50:58 am ---Maybe someone managed to upgrade to Windows 2K? --- End quote --- That's the one thing I think is impossible. The problem is that there's no 2K drivers for the acquisition controller. It's surprising that the 54845A can't be upgraded to a working 54846A. All the magic in these scopes are in the attenuator assemblies and A/D converters. Both models use the same parts - the A/D converters are part #1NB7-8353 and the Attenuator modules are 54512-63402 for both models. There must be some other minor modification needed... I still have this 54846A in my possession, and I have some scrap 54845A ACQ boards laying around. Maybe I'll do a in-depth comparison between the two today if I get a chance. |
| Jwalling:
Curiosity got the better of me and I couldn't resist waiting. Here's another difference I found on the solder side under PGA device U91 Two resistors are not installed on the 54846A! |
| Converter:
--- Quote from: Jwalling on November 12, 2017, 11:39:29 am ---That's the one thing I think is impossible. The problem is that there's no 2K drivers for the acquisition controller. --- End quote --- There is one guy on this forum who was able to modify the WinXP drivers for the oscilloscope LeCroy WavePro7k, that they now work in Win7. I do not exclude anyone could do or have already done similar and the drivers Agilent Win98. --- Quote ---It's surprising that the 54845A can't be upgraded to a working 54846A. All the magic in these scopes are in the attenuator assemblies and A/D converters. Both models use the same parts - the A/D converters are part #1NB7-8353 and the Attenuator modules are 54512-63402 for both models. --- End quote --- Yes, I'm also surprised at this. I tried to restart the calibration 3 times and always got a negative result. In this case, the test of the input channels gave an error almost instantly, as if he had seen forgery in advance. --- Quote ---Here's another difference I found on the solder side under PGA device U91 Two resistors are not installed on the 54846A! --- End quote --- Are you sure that the presence of these resistors is essential? It would be good to check this: remove these resistors and try to do the calibration procedure without them. If you get the same negative result as I do, it will be a breakthrough (by the way, what is the value of these resistors?). |
| Jwalling:
--- Quote from: Converter on November 12, 2017, 02:00:39 pm ---Are you sure that the presence of these resistors is essential? It would be good to check this: remove these resistors and try to do the calibration procedure without them. If you get the same negative result as I do, it will be a breakthrough (by the way, what is the value of these resistors?). --- End quote --- What I'm saying is that the 54846A does not have the resistors installed so there's nothing to remove. Your 54845A (if I'm right) has them installed. They are 261 Ohms in the 54845A. Looking a bit closer now; there may be a little more to this: The other two resistors right next to those that are installed in both boards have different values as well. On the 54845A they are 90.9 Ohms (marked in blue). In the 54846A (also marked in blue) they are 68.1 Ohms. |
| Converter:
--- Quote from: Jwalling on November 12, 2017, 02:53:46 pm --- --- Quote from: Converter on November 12, 2017, 02:00:39 pm ---Are you sure that the presence of these resistors is essential? It would be good to check this: remove these resistors and try to do the calibration procedure without them. If you get the same negative result as I do, it will be a breakthrough (by the way, what is the value of these resistors?). --- End quote --- What I'm saying is that the 54846A does not have the resistors installed so there's nothing to remove. Your 54845A (if I'm right) has them installed. They are 261 Ohms in the 54845A. Looking a bit closer now; there may be a little more to this: The other two resistors right next to those that are installed in both boards have different values as well. On the 54845A they are 90.9 Ohms (marked in blue). In the 54846A (also marked in blue) they are 68.1 Ohms. --- End quote --- I made changes according to your description. Removed 2 resistors 261 Ohms and replaced 2 resistors 91 Ohm by 68 Ohm. Unfortunately, after this absolutely nothing has changed. The calibration process is still without success. So I returned everything to its original state. |
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