Edu09 : Calibration failed (resolved)


#1

Hello,

I have just bought EDU09 and tried to assembled it.

Of course, as I am very new in electronic and solder actions this has not been so simple but the only real issue I encountered has been when I mounted R18 resistor in place of R28! When I unmounted R18 I broke it and replaced it with 2 resistors I had (in serial to obtain the same resistor value, I checked and it was apparently OK)

At the end, I plugged EDU09 to my PC and was happy to see the calibration OK (even if the led didn’t “light”)!

I tried then the advanced calibration as given by guide page 12 and then I saw strange and unstable values. I had a look on this forum and saw a post which said that it was due to bad “solder”. I check mines and saw that some of them was not very stable. So I re-soldered them and then problem occurs.

When I retried and obtained the following result:

  • The led did some light during a short time and the calibration result was:

Calibration results:
CH1 offset at 2V/div : 77 FAIL
Rounds : 51
CH1 offset at 1V/div : -46 OK
Rounds : 51
CH1 Y-position low, CH1_DAC1 196 0
Rounds : 33
CH1 Y-position mid, CH1_DAC0 196 77
Rounds : 51
CH1 Y-position high, CH1_DAC2 196 255
Rounds : 32

I then remembered me that I didn’t unmount IC’s when I re-soldered…

So my concern is now: have I destroyed something when I re-soldered? How to know?

Thanks in advance if you can help me!

Regards


Edu09 calibration failed
#2

Soldering with ICs mounted should not be a problem.

As a first test you may check the voltage on pin 1 of IC2.
When the USB cable is plugged in there should be about 1.5V.
When the EDU09 program is running, there should be 1.65V.


#3

Well, I suppose that the pin1 is at the level of the black dot on IC2 right?
If yes:

  • When the USB cable is plugged in = -0.56
  • When the EDU09 program is running = 2.47

Note that it is possible that I damaged the PCB when I unmounted the R18 resistor I had put wrongly in place of R28… could bad contact on R28 could be the reason?


#4

[quote]Well, I suppose that the pin1 is at the level of the black dot on IC2 right?[/quote]Yes, pin 1 is next to the dot.

[quote]could bad contact on R28 could be the reason?[/quote]No, but some damage on the board can be.

Please check the voltages on other IC2 pins too.

Here are the voltages measured on IC2 pins when USB cable plugged in:
1: 1.53V
2: 0V
3: 0V
4: -5.2V
5: 0V
6: 0V
7: -1.69V
8: 5.0V

Here are the voltages when the software EDU09 is running:
1: 1.63V
2: 0V
3: 0V
4: -5.2V
5: 0V
6: 0V
7: -1.69V
8: 5.0V


#5

Hello,
First of all, thanks for your efficient support.

Secondly I tried to measure as requested. The problem is that some values change during measurement! But I think that the biggest problem is that I never find same values than you.

Assuming that pin are counted anticlockwise

Side 1(Dot side) Side 2
Pin 1 Pin 8
Pin 2 Pin 7
Pin 3 Pin 6
Pin 4 Pin 5

Here are the voltages measured on IC2 pins when USB cable plugged in:
1: 1.53V ==> 0.86
2: 0V ==>0.30
3: 0V ==> 0.16
4: -5.2V ==> 0.48
5: 0V ==> 0.08
6: 0V ==> 2.20
7: -1.69V ==> 0.45
8: 5.0V ==> 1.81

Here are the voltages when the software EDU09 is running:
1: 1.63V ==> 0.69
2: 0V ==> 0.77
3: 0V ==> 0.32
4: -5.2V ==> 0.69
5: 0V ==> 0.26
6: 0V ==> 3.26
7: -1.69V ==> 0.69
8: 5.0V ==> 2.58

As you can see value as all differents! So the big question is: may be it would be better to re-buy another kit and to re-build from scratch (as said I am a beginner with the classical error cycle : error <=> success )


#6

The results are very strange.
For example on pin 8 there should be voltage +5V, which is coming directly via L1 from the USB socket.
If L1 is properly soldered and not broken, there should be +5V on pin 8.
Please make sure you have a good ground reference for the DVM when doing the measurements.
You can use the USB socket’s “shield” as the ground reference.
Please make sure the shield is properly soldered to the ground plane of the board.

If there is still no +5V on pin 8, you can check if there is +5V on the wires of L1.

[quote=“Meziane”]The led did some light during a short time [/quote]This is also very strange.
The LED is connected via R8 to USB socket’s +5V. The LED should lit immediately when the USB cable is plugged in.
Please check the USB connector soldering.


#7

Hello,

Thanks to you I did some progress.

The issue with the led seems solved. The solder of 1 usb pin was not to good. I fixed it and I also saw that my USB plug was not 100% compliant with the socket. Thus I tried several deep to plug it and I have found that I needed to plug it only at 85% deep (sorry but as Engligh is not my native language, some terms are missing from my vocabulary!).

I retried a calibration and obtained the following results:

CH1 offset at 2V/div : 128 OK
Rounds : 5
CH1 offset at 1V/div : 56 FAIL
Rounds : 51
CH1 Y-position low, CH1_DAC1 66 0
Rounds : 33
CH1 Y-position mid, CH1_DAC0 120 179
Rounds : 51
CH1 Y-position high, CH1_DAC2 138 255
Rounds : 32

I checked L1 and L2 (there are chokes right?) and results are:

L1: 1.47
L2: 5.07

Here are the voltages measured on IC2 pins when USB cable plugged in:
1: 1.53V ==> 1.44
2: 0V ==>0.34
3: 0V ==> 0.19
4: -5.2V ==> 0.45
5: 0V ==> 0.16
6: 0V ==> 2.20
7: -1.69V ==> 0.45
8: 5.0V ==> 1.48

Here are the voltages when the software EDU09 is running:
1: 1.63V ==> 2.5
2: 0V ==> 1.4
3: 0V ==> 0.34
4: -5.2V ==> 0.69
5: 0V ==> 0.34
6: 0V ==> 3.27
7: -1.69V ==> 0.70
8: 5.0V ==> 2.60

Regards


#8

[quote=“Meziane”]I checked L1 and L2 (there are chokes right?) and results are:

L1: 1.47
L2: 5.07[/quote]This seems to indicate that the +5V from the USB is properly coming to L2 but not to L1.
So also the whole input section (IC1, IC2) is not getting the +5V supply.
Please check why there is no +5V on L1.
The +5V should appear on both ends of the L1.

Also it seems that the charge pump is not working.
There doesn’t seem to be -5.2V on pin 4 of IC2 as should be.

During the calibration there must have been -5.2V on this pin.
If no -5.2V, the calibration should fail different way.
Here are the calibration results if charge pump is not working:

Calibration results:

CH1 offset at 2V/div : 77 FAIL
Rounds : 51
CH1 offset at 1V/div : -46 OK
Rounds : 51
CH1 Y-position low, CH1_DAC1 201 0
Rounds : 33
CH1 Y-position mid, CH1_DAC0 201 77
Rounds : 51
CH1 Y-position high, CH1_DAC2 201 255
Rounds : 32

Seems about similar as the results in your first post.

For more details please see this thread:
viewtopic.php?f=46&t=9325


#9

Well, I solved the issue with L1 and now I have:
5V on L1 (it was due to a bad solder)
5V on PIN 8 of IC2

Other value on IC2 are always bad. I checked T1, T3 and T2 but I didn’t see any problem. How can I test them with à voltmeter?


#10

If you now run the calibration, what is in the Calibration.log ?

It seems there may be other soldering or assembly problems on the board.
Please check carefully all soldering joints.

If everything seems to be OK, you can then check the charge pump voltages on following points:


#11

Now calibration result is :

CH1 offset at 2V/div : 83 FAIL
Rounds : 51
CH1 offset at 1V/div : 56 FAIL
Rounds : 51
CH1 Y-position low, CH1_DAC1 19 21
Rounds : 51
CH1 Y-position mid, CH1_DAC0 181 85
Rounds : 51
CH1 Y-position high, CH1_DAC2 203 255
Rounds : 32

As you can see it is always the same. I am going to re-chek soldering points and also the charge pump voltages. Thanks for the diagrams. I’ll keep you updated… but I think not before several days.

Once again, thanks for your help.


#12

OK - No problem and no hurry :slight_smile:

Here are the charge pump voltages as a reference measured on working EDU09:
A = 1.67 V
B = 0.44 V
C = 4.40 V
D = 3.09 V
E = -2.61 V
F = -5.22 V


#13

Hello,

I reviewed al soldered points and fixed several. Now I am happy to say that calibration is completed successfully and that measured voltages are compliant with those you mentioned. So a big thanks to you!

I tried also the advanced calibration as said into the guide page 12. Unfortunately I did’nt succeed.

When I launch the advanced calibration (DC mean) without plug the external battery, I have between -0.81V and 0.81V depending on RVI trimmer position.
When I connect the battery, I obtain the same values. Thus I suppose that it remains something wrong with my build. Could you say me how I could identify where is the problem (I’d like to avoid to have a regression and I’d like to modify only what is needed).

Thanks in advance

Regards


#14

It’s nice to see that your EDU09 is working!

[quote=“Meziane”]When I launch the advanced calibration (DC mean) without plug the external battery, I have between -0.81V and 0.81V depending on RVI trimmer position.[/quote]This is normal result when the RV1 is adjusted.

[quote=“Meziane”]When I connect the battery, I obtain the same values.[/quote]This indicates broken connection in the input section.
Please make sure Coupling DC is selected (I think it is OK. This is the default setting when the software is run.)

[quote=“Meziane”]Note that it is possible that I damaged the PCB when I unmounted the R18 resistor I had put wrongly in place of R28… could bad contact on R28 could be the reason?[/quote]This can be the cause of the problem.
You can check the continuity by following way:

  • Disconnect the USB cable.
  • Measure resistance between the input clamp (Red) and IC1 pin 1.
    There should be 75k ohm resistance between these points.

If not, check R28 connection.
If OK, check the input cable (red) connection.
If OK, heck the Ground input cable (black) connection.

When you get the input section working, you can do the advanced calibration.

Here are more detailed instructions how to proceed:
• In the ‘Options’-menu select “Expert Settings”.
• In the ‘View’-menu select “Waveform Parameters…”.
• In the ‘Waveform Parameters’-window select the check box “DC Mean”.

• Adjust RV1 to its middle position

  1. Connect the input cables red and black together.
  2. Select Options -> calibrate
  3. Measure the output of the battery with a multimeter and remember it.
  4. Connect the battery to the oscilloscope’s input.
  5. Set Volts/Div. to “0.5V” and click the “Run”
    button.
  6. Adjust trimmer RV1 until the displayed “DC
    Mean” value in the ‘Waveform Parameters’-
    window corresponds with the measured value.
  7. Remove battery.

If you had to adjust RV1 a lot, repeat the steps 1 to 7.


#15

Hello,

Well the cause is R28. As said at the beggining of my post, I initially did a mistake and wrongly soldered R18 at the R28 place. I unsoldered R18 and soldered R28 but I think that I damaged the PCB at the R28 place. Any means to workaround this?


#16

[quote=“Meziane”]I unsoldered R18 and soldered R28 but I think that I damaged the PCB at the R28 place. Any means to workaround this?[/quote]You may try to locate the trace break and fix it.
In this picture is shown a section of the PCB.
Please check that all the red points are connected together and also all the blue points are connected together.
If you locate disconnected points, you can solder a copper wire between them on the bottom side of the board.
Be careful not to make short circuit to the ground plane.


#17

Hello,

Thanks a lot for the pcb picture. This helped me a lot. I succeeded to wire between points (In fact it was only around R28)…

After I did a standard calibration and it has been completed successfully (you can imagine that I was a lot happy). I tried then the advanced calibration but has difficulties to adjust with VR1. I did several time and at a moment I decided to reinitialize EDU09 and to do again a standard calibration and this time it failed.

I measured then voltage on IC2 pins and now I have 3.44V on pin 1 (all others pin are OK). I tried to check again solderes points but find nothing. What could I check to solve this last issue (I hope that this will be the last)


#18

It seems there may be bad solder joint on one of these components: R27, R9 or R10.
If all OK, check also solder on pin 12 of IC3.


#19

I checked several times and all are OK. Any other possibility to investigate?


#20

To make sure they are all OK, please do following test:

  • Disconnect the USB cable.
  • Measure the resistance between these points: pin 12 of IC3 and pin 2 of IC2

There should be 22 k ohms.