Hello,
My PCSU1000 is failing calibration at startup, specifically Ch1 cals fail:
Calibration results:
CH1 offset at 2V/div : 174 FAIL
CH2 offset at 2V/div : 117 OK
CH1 offset at 1V/div : 51 FAIL
CH2 offset at 1V/div : 7 OK
CH1 offset at 0.5V/div : 51 FAIL
CH2 offset at 0.5V/div : -2 OK
CH1 offset at 5us/div : 201 FAIL
CH2 offset at 5us/div : 2 OK
CH1 Y-position low 0
CH1 Trigger : 255
CH1 Trigger : 0
CH1 Trigger low : 128 OK
CH1 Y-position mid 0
CH1 Trigger : 255
CH1 Trigger : 0
CH1 Trigger middle : 128 FAIL
CH1 Y-position high 0
CH1 Trigger : 255
CH1 Trigger : 0
CH1 Trigger high : 128 FAIL
CH2 Y-position low 31
CH2 Trigger : 55
CH2 Trigger : 39
CH2 Trigger low : 47 OK
CH2 Y-position mid 127
CH2 Trigger : 100
CH2 Trigger : 81
CH2 Trigger middle : 90 OK
CH2 Y-position high 223
CH2 Trigger : 145
CH2 Trigger : 124
CH2 Trigger high : 134 OK
EXT Trigger middle : 42 OK
By using the method you suggested about changing the windso.ini entry HWdialog to “0” I was able to get Ch2 working fine.
I suspect Ch1 got overvoltaged at some point. I’d like to troubleshoot Ch1, by looking at the log data above can you suggest what parts might be suspect so that I can check and replace them if necessary?
My unit’s S/N is 200701684. PCLab is running on W7 Ultimate, 64 bit.
I really appreciate your help! Let me know if you need any further information.
Best regards,
Blake
Did you follow the instructions in this thread to get the scope working:
[forum.vellemanprojects.eu/t/pcsu1000-chan1-killed-by-overvoltage-calibration-failed/5571/1)
Thank you so much for the quick reply! Yes, I followed that thread to get past the calibration error, and now I will follow your other suggestions for getting the bad channel to work. I’ll check IC11, the OPA354 that is in the Ch1 circuit (that’s the channel that is not working in my unit) and the diodes D6 and D8. In the post you noted in your reply you are helping a person get Ch2 working, and you mentioned checking D3 and D4. I’m looking at the schematic and D4 is the back-to-back diode package at the input to IC6A, the LMV7219. Is that the diode you intended to have him check?
I’m sorry I referred wrong channel input amplifier.
Indeed, IC11 is the input amplifier of CH1.
Yes, check IC11, D6 and D8.
[quote]I’m looking at the schematic and D4 is the back-to-back diode package at the input to IC6A, the LMV7219. Is that the diode you intended to have him check?[/quote]I’m sorry, the D4 was wrong reference in the other post. Should be D2.
Hello,
I replaced IC11 the OPA354, and I am now able to see signals on the scope for that channel. However, I still get a calibration failure with these results:
Calibration results:
CH1 offset at 2V/div : 123 OK
CH2 offset at 2V/div : 117 OK
CH1 offset at 1V/div : 3 OK
CH2 offset at 1V/div : -1 OK
CH1 offset at 0.5V/div : 10 OK
CH2 offset at 0.5V/div : -2 OK
CH1 offset at 5us/div : 1 OK
CH2 offset at 5us/div : 1 OK
CH1 Y-position low 32
CH1 Trigger : 59
CH1 Trigger : 35
CH1 Trigger low : 47 OK
CH1 Y-position mid 127
CH1 Trigger : 99
CH1 Trigger : 79
CH1 Trigger middle : 89 OK
CH1 Y-position high 223
CH1 Trigger : 143
CH1 Trigger : 124
CH1 Trigger high : 134 OK
CH2 Y-position low 0
CH2 Trigger : 255
CH2 Trigger : 0
CH2 Trigger low : 128 OK
CH2 Y-position mid 128
CH2 Trigger : 101
CH2 Trigger : 82
CH2 Trigger middle : 92 FAIL
CH2 Y-position high 223
CH2 Trigger : 147
CH2 Trigger : 124
CH2 Trigger high : 136 OK
EXT Trigger middle : 42 OK
Looks like the only failure is the CH2 Trigger middle.
Can you suggest how to troubleshoot that? Also, after the failed calibration, I set HWdialog=0 and restarted the program. I am using two similar probes and attaching them to the same signal source. There is a phase shift between the two signals, a scale difference, and the Ch1 waveform does not look exactly the same as the Ch2 signal. Also, the Ch1 trace disappears when setting the scope gain to greater than 0.5V/div (0.2V/div and on do not work). Does that sound like a familiar problem? I [img][img]can send you a screen shot of the scope display if that would help.
Thank you for the quick response. Yes, performing the Options -> Calibrate function did indeed result in a passed calibration. But I still think I have a hardware problem because the two channels do not show the same waveform when I attach probes to the same signal source. The difference starts to occur at frequencies above about 10kHz. Channnel 1’s display begins to attenuate, while Channel 2’s display shows what I expect, the signal amplitude stays constant as I change the signal generator’s frequency. The signal generator output has about a 3V DC bias, so I set the scope for AC coupled. Setting Ch1 sensitivity at .2V/div, .1V/div or 50mV/div causes the display to dramatically distort and go off screen. Ch2’s display, AC coupled, always stays centered in the display as I change that channel’s sensitivity. I suspect there is another hardware problem that needs solving, can you suggest what could be causing this problem?
Hello and thanks for the suggestions. I replaced D6 and D8, and checked both R56 and C43 which were ok, but I am still having the same problem, where the signal amplitude displayed on the scope is dependent on the frequency, and the scope trace disappears once I set the sensitivity past .5V/div. This is very different from the behavior of Ch2. Any additional suggestions? I could try replacing IC12A but let me know if that is wise to do. Definitely changing IC11A was a help as it must have been damaged, but perhaps the design is such that IC11A protects the LMH5724.
You may use the working CH2 probe to check the signal at the output of IC11 (pin 6) and then at the outputs of IC12A and IC12B (pin 1 and pin 7).
I think you’ll locate the amplifier where the signal is distorted and where the DC level changes a lot when using ranges past 0.5V/div.
Hello,
I located the problem. Once I replaced IC11 and got a working signal I worked backwards, comparing the two channels measuring the same function generator signal and probing with another scope. What was happening was R48 had somehow become a large resistor, 25 kOhms, instead of 10 Ohms, and when the .2V/div button was clicked the signal essentially went away at the positive input of IC11, pin 3, with probably a tiny amount of offset, and so the opamp drove its output to the negative rail, causing the PCSU1000 to go off scale on Ch 1. Thank you for your help, I just have to replace R48 with a chip resistor now.
It would be helpful to have a table of which button activates which relay on the PCB, that was a bit difficult to figure out. But I believe the .2V/div button switches relay RY9 closed, while RY10, 11 and 12 stay open. Is that correct?
I replaced R48 and everything works as it should. That table is very helpful, thanks for posting it! I was expecting to see R9 closed for the .2V/div condition, though. I’ll go back to the schematic now that I have this info and see how a high-resistance for R48 would cause the problem.
