Calibration problem with K8031

Kits PC Related Projects
1

Sir;

I have just completed assembly of my K8031 and while trying to calibrate the device, I noticed that my trace is at the top of the screen and I am unable to adjust it with the slider.

I have read all of the forum posts on this subject and applied their suggestions without success. i.e. checked solder joints, component placement, measured the R10, R8 and R7 resistors (all are within spec) etc.
I have been listening to the reed relays as they click but I’m unsure which relay should click when different ranges are selected.

I was wondering if there are any papers available on how the input circuits work and troubleshooting procedures when they don’t work. If there are no papers perhaps you can suggest the next steps I should take to troubleshoot the scope?

One last newbie question …when using the Probe100 where do I connect the ground alligator clip?

2

I’m sorry, no documents available.
The relay operation is following:
3V/div: RY4 on, RY5 off, RY3 off, RY2 off
1V/div: RY4 on, RY5 on, RY3 off, RY2 off
0.3V/div: RY3 on, RY5 off, RY4 off, RY2 off
0.1V/div: RY3 on, RY5 on, RY4 off, RY2 off
30mV/div: RY2 on, RY5 off, RY3 off, RY4 off
10mV/div: RY2 on, RY5 on, RY3 off, RY4 off

Coupling DC: RY1 on
Coupling AC: RY1 off

To locate the problem you may check the voltage on pin 1 and pin 7 of IC3.
The voltage on pin 7 should be adjusted with RV1 to between the voltage levels on pins 9 and 4 of IC4.
To get the trace to the middle line of the screen the voltage on pin 7 of IC3 should be about 2.3V.
The voltage on pin 9 of IC4 should be about 3.2V and on pin 4 about 1.4V.
You can use the heatsink of the voltage regulator IC15 as the ground reference point for the voltage measurements.

3

Thanks for the information. I will let you if this solves the issue.

4

Vel255;

I`ve followed your reccommendations with the following results:

3V/div: RY4 on, RY5 off, RY3 off, RY2 off - worked
1V/div: RY4 on, RY5 on, RY3 off, RY2 off - worked
0.3V/div: RY3 on, RY5 off, RY4 off, RY2 off - worked
0.1V/div: RY3 on, RY5 on, RY4 off, RY2 off - worked

30mV/div: RY2 on, RY5 off, RY3 off, RY4 off - RY1 changed to OFF from DC to AC
10mV/div: RY2 on, RY5 on, RY3 off, RY4 off - RY1 chnaged to OFF from DC to AC

My conclusion is that the reed switches are working in the 1v, 3v,.3v etc.

…The voltage on pin 7 should be adjusted with RV1 to between the voltage levels on pins 9 and 4 of IC4.

Pin7 was set to 2.3v

…To get the trace to the middle line of the screen the voltage on pin 7 of IC3 should be about 2.3V.
…The voltage on pin 9 of IC4 should be about 3.2V and on pin 4 about 1.4V.

Pin 9 voltage 3.2V
Pin 4 voltage 1.4V

[b]Can you tell me what happens once the IC3 pin 7 voltage is fed into IC4 pin 8, what output should I see leaving IC4 going over the parrel cable to the computer. I`m beginning to suspect that the IC4 may have a fault. (I did take it out and inspected the pins, polarity and soldering etc).

Once again thanks for the help![/b]

5

The data is fed in serial mode to the PC via optocouplers IC18 and IC22.
You may do following indicative test to check the data and the optocouplers IC18 and IC22:
Run the PC program and click the ‘Run’ button to start the ‘run’ mode.
Check the voltage on pin 3 of IC18 and IC22.
There should be varying voltage:
IC18 pin 3: 2V-2.4V
IC22 pin 3: 4.1V-4.3V

Now click the Run button ‘up’ to stop running.
Now there should be constant voltage:
IC18 pin 3: 1.7V
IC22 pin 3: 3.5V

[quote]Can you tell me what happens once the IC3 pin 7 voltage is fed into IC4 pin 8, what output should I see leaving IC4 going over the parrel cable to the computer.[/quote]You can check the operation of IC4 by following way:
Run the PC software and click the ‘Run’ button to start the ‘run’ mode.
Use RV1 to adjust the voltage on pin 7 of IC3 (same as pin 8 of IC4) to 2.2V.
Now check the IC4 output pins 12, 13 and 14.
Should be:
12 = low (about 0V)
13 = high (> 4V)
14 = high (> 4V)

Now adjust the pin 7 of IC3 to 2.4V.
The IC4 outputs should be:
12 = high (> 4V)
13 = low (about 0V)
14 = low (about 0V)

6

Vel255;

I am pleased to report that my issue has been solved. It turns out that pin 5 on IC22 was bent under the chip. Once I traightened the pin the scope worked as advertised!

I would like to compliment you on your knowledge level on this device. Your instructions were spot on and instrumental in solving this issue. Well done.

Satisfied Customer