Hello
I’ve assmbled my new K8031 yesterday and i cant get it work. Accually i got a few problems.
My computer says it cant communicate with the device but i can hear the realy click when i press the “3V” button and the “0,3V” button in PC lab 2000 se. I ran a small program that lets me monitor the parallel port states and i can see that it is comming some kind of data from the K8031 but i get no signal on the screen. PC lab seems to be connecting on my other computer becouse it does not show any message about communication error but still no singal on the screen. What components can i check to find out whats wrong?
Maybe the data you got from the K8031 is either 255 or 0. In this case there is nothing seen on the screen.
You may start by checking the A/D converter section.
Check the input voltage on pin 8 of IC4. It should be something in between the reference voltages VRT on pin 9 and VRB on pin 4.
I measured following values when the trace is in the middle of the screen:
pin 8: 2.3V
pin 9: 3.2V
pin 4: 1.4V
These values are measured against the power supply ground plane. You’ll see easily the isolation barrier on the PCB between the power supply ground plane and the “floating” input section ground plane.
The probe input BNC connector’s ground is connected to the input section ground and should be about +2.5V compared to the power supply ground plane.
Thank you for the quick answer.
I measured the pins on IC4 and i get almost the same as you did.
pin 8: 2.6V
pin 9: 3.2V
pin 4: 1.4V
The probes both pin is 2,42V.
Ive found a test program somewhere in the PC lab cd that came with K0831. That test program lets me read from the K8031 ram and it says nothing but 0.
The A/D converter voltages are OK.
Next you can check the optocouplers IC26 and IC27.
- Check the position.
- Check the voltage between pins 8 and 5 should be about 3V.
- On pin 6 there should be some variation in voltage when data is transmitted from scope to PC.
The voltages should be measures against the LPT cable GND. E.g. C47 GND pin.
I just measured on pin 5 and 8 IC22 and IC18. i think it is the output, i didnt have IC26 or IC27.
IC18 is okay i can see the variations but IC22 doesnt seem to work on both K8031 side and the parallel side.
Accually when i started my K8031 after soldering i discovered that all optocouplers were faultily assembled. So i just put them all right and it seems that they survived.
Sorry - the IC18 and IC22 are the right ones. (I checked first wrong circuit diagram.)
You may check the IC22 (possible faulty) by swapping it with one of IC19, IC20 or IC21.
I swaped them but its still the same. I also measured on IC6 pin 9. I belive that pin 9 is the second nibble in the output. It seems to me that somering is wrong with IC6 because it is constant 4,96V and the A output is always changing. With the program i have on the computer i can see that the parallel port pin 10 is constant 1 and pin 12 is changing from 1 to 0 very fast seems to be data comming from 12.
The pin 9 of IC6 should be about 2.4V when the Run button is down and the trace is in the middle of the screen. There is 0.5V when the trace is at the bottom of the screen and 3.2V when the trace is on the top of the screen.
What do you see on pin 1 of IC6?
There should be about 2V when the Run button is down and 5V when Run button is up.
All the tests are made with Trigger OFF.
Pin 2 of IC6 is 3.6V when Run on and 5V when Run off.
Pin 14 of IC6 is 1.5V when Run on and 0V when Run off.
Pin 9 is always 0.42V. Is the trace the slider in “Volts/div” named “Position” in PC lab?
Pin1 is changing from 2.14V, 2.28V, 1.82V 1.14V and some more when in run. When not running it is about 5V. Pin 2 is changing from 3V and 3.45V and 3.6V in run mode, and about 5V when off. Pin 14 is switching between 1.89V and 1.43V. Pin 14 is 0V when not running.
I think i made a discovery today. I think IC6 is working alright accually beacuse today when i was testing the voltages the pins on IC6 and suddenly i saw something in the PC program. That time i had IC4 removed and when i touched some pins on IC6 with anything metal i saw some kind of singals. And when i put IC4 back i could not see anything again. I think that the error is somewhere between IC3 and IC4.
[quote]Pin 9 is always 0.42V. [/quote]This is strange. Should change when the “Position” slider is changed and “Run” button is down.
[quote]Is the trace the slider in “Volts/div” named “Position” in PC lab?[/quote]Yes.
Pin1, pin 2 and pin 14 values are OK. The variation of the voltage is OK too. I just put in the list some average values to indicate the level.
You can check the IC4 operation by checking its output pins while moving the “Position” slider up and down. The “Run” button must be pressed.
When “Position” is at the bottom, all the IC4 outputs should be low.
When “Position” is at the top, all the IC4 outputs should be high (about 4.3V).
The output on IC4 is always low around 0.29V. Pin 7 on IC3 is 0.01V when “Position” is down at the bottom of the slider, 0.75V when in the middle and 2.40V at max. Pin 3 on IC3 is 2.39V when the probe is out and if i messaure a battery it still shows 2.39V.
[quote]The output on IC4 is always low around 0.29V.[/quote]This indicates the IC4 is not working.
There should be outputs high if the input voltage (pin 8 ) is above the bottom reference voltage (VRB pin 4).
Please check the CLK pin 16 and CE pin 22. Both should be about 3V when Run on.
You may use RV1 to increase the “virtual ground” to about 2.5V. You can measure it from the ground terminal of the probe connector against to the power supply ground plane.
I get around 3V on pin 16 and 22.
If IC4 is broken how do i get a new one?
Most probably there is some “external” reason why the IC4 is not working.
There may be bad connection to some of the pins to the socket, bad soldering or a solder bridge between pins.
When everything is checked and if the outputs of IC4 are low regardless if the input level is in correct range in Run mode, this may indicate the IC is defective.
In this case you can send e-mail to support@velleman.be and ask how to proceed.
I have overlooked my the soldering and the PCB board but i can not find any defects.
Mabye i can test it? I was thinking that i could test IC4 with a PIC processor. That should give a straight answer, right?
How do i use IC4? do i need to have those capacitors that comes in to pin 9, 4, 5 and 17?
Would you like to tell me how i can easily test it?
I think you may still do some tests on the board.
There is separate supply voltage pin for the output section of this circuit. It is pin 19.
Please check the voltage on pin 19 of the IC4.
Check also pin 18 and pin 21 voltage. All should be about 5V.
Check also pin 17. There should be about 1.4V.
Have you checked all the eight outputs of the IC4 when the position slider is in the top position? - And Run button is pressed down.
All eight outputs are around 0.24V even if the slider is at bottom or up and running. Pin 19 is 4.95V, pin 18 is also 4.95V and pin 21 is the same. Pin 17 goes up and down between 2.32V to 1.89V.
This results are strange:
Outputs 0.24V.
- The low value of the outputs should be <0.1V.
Pin 17 goes up and down between 2.32V to 1.89V.
- Pin 17 should be stable 1.4V
According to all these results, it seems the IC4 is defective.
You can contact support@velleman.be and ask how to proceed.