Hello,
I have made a short circuit with my input probe (ground probe linked to 12V)!
Since then, my oscilloscope does not work. In fact the calibration starts but always fails.
The calibration log indicates the following :
Offset at 3V/div : -24 FAIL
Offset at 1V/div : -51 FAIL
CH1 correction at 20us/div : -101 FAIL
CH1 correction at 10us/div : -101 FAIL
CH1 correction at 4us/div : -101 FAIL
What can I do? Is this possible to have it repaired?
Yhank’s for your answer
If you connected the probe ground to the +12 V of the power supply then some of the components of the input section of the scope may be defective: Most probably the analog switch IC4.
First use a multimeter to check the voltage between the probe ground and the GND terminal of the power input connector. The voltage should be about 2.5V.
If the voltage is about zero or +5V then most probably the IC4 is defective.
If you have proper tools and skills you may remove IC4 and check the voltage between the probe ground and the GND terminal again. If about 2.5V you may run the PCS100 software, but before running it please replace the content of the WinDso.ini with the following text. No calibration occurs and the default settings are used.
If only IC4 was faulty then your scope should work but the input selection GND should not work properly. Also calibration will fail.
[Status]
Running=0
[ScopeMainForm_100]
Top=1
Left=1
Width=719
Height=560
Status=1
[EditForm_100]
Width=293
Height=262
[EditForm_100rec]
Width=294
Height=259
[Calibration_100]
f20us_offs=0
f10us_offs=0
f4us_offs=0
offs_1=128
V1_offs1=0
V30mv_offs1=0
V10mv_offs1=0
Ch1_pos0=128
Ch1_pos1=32
Ch1_pos2=224
Ch1_ad0=128
Ch1_ad1=192
Ch1_ad2=62
[Hardware]
DemoMode=0
LPT_Port=1
LPT4=888
[Menu_100]
HWdialog=0
RMS_on=0
dBm_on=0
Rate_on=0
Rec_Rate_on=0
Hide_Scope=0
LPT_Speed_Slow=0
[Colors_100]
DefaultColors=1
Background=0
Ch1=65535
Dark_Grid=8388608
Bright_Grid=16711680
Time_Marker=16776960You may have to change in the Options/Hardware setup menu the LPT port address if not 378.
Thank’s very much for your answer.
I have checked the voltage between the probe ground and the GND terminal of the power input connector and found around 2.4V.
Then I have run the PCS 100 software after having replaced the content of the WinDso.ini with the text you proposed .
Indeed, no calibration occured but I have no trace on the screen and no signal…
Do I need to remove the IC4 circuit?
Do not remove the IC4. Most probably it is not defective and there is some other faulty component on the board.
Next you may check the voltage on pin 7 of the IC5. Probe removed.
Thank’s for answering,
I have disconnected the probe.
For the voltage on pin 7 of IC5, I have found 2,6V (I hope, I made the mesure on the right pin!)
The measured voltage looks OK.
The trace is normally visible on the screen when the voltage is between 2V and 3V (about).
Adjusting the Y-position slider changes the voltage from 1.6V to 3.4V (about).
If this is the case then the input section of the scope seems to be OK.
Next you can check the AD converter IC9 operation.
There are seven vias on the right side of the IC9 near the text “IC6”. These are connected to the output lines of the AD converter IC9.
Adjust the Y-position slider to lowest position and click Run button.
Measure the voltage of those seven vias against the GND. Voltage should be about 0V.
Adjust the Y-position slider to uppermost position. The voltages of the vias should be about 4.9V.
On pin 7 of IC5, I find 1,9V for the lowest Y-position slider and 2,8V for the upper position.
For the 7 vias on right of IC9 (near IC6 text),
when Y-position slider is down , I read around 0V for all of them
when Y-position slider is at the uppermost position, 2 of them are at 5,1V, 2 are about 0V, three are not constant (change between 1,5V and 3V).
Just a slight clarification,
-I see a trace only on the “30mV” caliber
-for the mesure on pin 7 of IC5, the values I gave are with the trace visible down the screen (Y-position slider just above middle) and the second one when the Y-position slider is uppermost.
You get the trace on the screen on the 30mV/div range. This and the measurement results indicate that the AD converter seems to be OK.
Next steps (probe removed):
Switch to 10mV/div voltage range: Is the trace still visible on the screen?
If yes: Adjust RV1 until the trace is in the middle of the screen.
If not visible, please make the following tests:
On 10mV/div voltage range:
Select 30mV/div voltage range.
I have selected the 30mV/div range , set the Y-position slider to the center and adjusted RV1 until the trace was in the middle of the screen.
I had to turn several turns with the screw driver.
I noticed also that the trace did not stay in the middle of the screen when I put the cover on the oscilloscope (or put something on the top of the box)
Then I have selected the 10mV range. The trace is still on the screen (shifted down about 1 div).
It is normal that the trace position changes if you have the cover opened and close it. The components (D1 and D2) are light sensitive and thus the offset adjustment should be done in as dark environment as possible.
Now you got also the 10mV/div range working.
Where the trace is on other V/div ranges? Is it visible on the screen?
Is the difference in the trace position between 10mV/div and 30mV/div ranges one big division or one minor division on the screen?
There is no trace visible on the screen for the others ranges (3V, 1V, 0,3V, 0,1V). In thoses cases, the tension on pin 7 of IC5 is about OV.
When I swich from 30mV to 0,3V or 0,1V, the trace goes down quickly (almost vertical) and disappears
When I swich from 30mV to 3V or 1V, the trace just disappears.
The difference of the position of the trace between 30mV and 10mV is about 1,5 division (=1,5 space between horizontal lines (= small division?) )
Tension is about 2,4V for 30mV range and 2,2V for 10 mV.
It seems that one (or more) of the analog switches IC1, IC2 or IC4 is defective.
Again, thank’s very much for your help.
If I can find those circuits, I can change them. Are they standard circuits? Where can I find them?
It seems that IC4 is defective.
You may get your scope mainly working after removing it.
After removing the IC4, select 10mV/div range and adjust RV1 until the trace is seen on the screen and is about in the middle of the screen.
Check if the other V/div ranges work.
If OK then switch between 1V/div range and 3V/div range and continue to adjust RV1 until the trace stops to ”jump” when the V/div range is changed.
The ananlog switch is NXP, Philips type: 74AHC1G66GW (package SOT353).
Datasheet:
standardics.nxp.com/products … ct1g66.pdf
Ok, I am going to remove IC4 and I keep you informed.
Which funcgtions will not be available afer that?
What is the purpose of RV2?
Thank you!
The coupling “GND” will not work properly. Also calibration may fail if you try it by deleting the WINDso.ini.
If you have SMD removal tools and experience how to remove SMD components then no problem.
If you haven’t, then be very careful when removing the part!
If you have two soldering irons then the remove is easy. If you have only one then the easiest way to remove the IC4 is to add a lot of solder over it’s soldering points and then heat all of them until all the solder melts. Then just slide the IC away with the soldering iron. Do not use force!
Finally clean the soldering pads with desoldering braid (Solder wick).
The RV2 is for gain adjustment.
I have removed IC4.
Now I have a trace on all ranges (3V, 1V, 0.3V, 0.1V, 30mV, 10mV) : very good!
But I notice the following :
1- When I adjust RV1 to have the zero in the middle of the screen (trace in front of the ground symbol, in the middle of the screen) on the 3V range, this is Ok for 0.3V and 30mV ranges. But when I switch to the 1V or 0.1V or 10mV range, the trace is shifted almost one division down (1 line down) the ground symbol (same position for 1V, 0.1V, 10mV). When I adjust RV1, the trace moves the same way for all ranges.
2- For one range, when the trace is adjusted in front of the ground symbol in the middle of the screen, if I move the Y-position slider to the bottom (or the top), the trace is no more in front of the ground symbol. When the trace is at the lowest visible position, the ground symbol is 3/4 division (line) above. When the trace is at the upper visible position, the ground symbol is 3/4 division under.
That is good news.
There are still some problems due to that the adjustment of RV1 is not yet complete and the self calibration is not possible.
When you adjust RV1 it seems that all traces move same way but actually at 1V, 0.1V and 10mV ranges the trace moves three times “faster” than on 3V, 0.3V and 30mV ranges.
Switch continuously between 1V and 3V ranges and adjust RV1 until the trace is in same position on the screen on both ranges. Do not try to adjust it in the middle of the screen just adjust until it stops “jumping”.
This is the only manual adjustment. Normally the rest is handled by the automatic calibration process.
If you find the stable place for the traces about same position as I found (about two small divisions above the middle line), you may use my calibration results.
After the manual adjustment of RV1 is complete, close the program. Replace the content of the WinDso.ini file with the following data.
Hope it helps a little…
[Status]
Running=0
[ScopeMainForm_100]
Top=1
Left=1
Width=719
Height=560
Status=1
[EditForm_100]
Width=293
Height=262
[EditForm_100rec]
Width=294
Height=259
[Calibration_100]
f20us_offs=1
f10us_offs=2
f4us_offs=4
offs_1=133
V1_offs1=-1
V30mv_offs1=0
V10mv_offs1=0
Ch1_pos0=127
Ch1_pos1=32
Ch1_pos2=224
Ch1_ad0=133
Ch1_ad1=184
Ch1_ad2=81
[Hardware]
DemoMode=0
LPT_Port=1
LPT4=888
[Menu_100]
HWdialog=0
RMS_on=0
dBm_on=0
Rate_on=0
Rec_Rate_on=0
Hide_Scope=0
LPT_Speed_Slow=0
[Colors_100]
DefaultColors=1
Background=0
Ch1=65535
Dark_Grid=8388608
Bright_Grid=16711680
Time_Marker=16776960
The final solution is to get a new analog switch IC4 anyhow…
Congratulations, You are very good!! It is very well.
I have done what you said and found also almost 2 division above the middle where the trace did not move between 3V and 1V ranges.
I have changed the WinDso.ini file for yours.
There is now just a slight movement of the trace (width of the line) when I switch from 3V to 1V.
The only little problem which remains is that when input = 0V, the trace is not exactly in front of the ground symbol (a bit above). Which parameter of the WinDso.ini file do I need to change?