Dear Velleman
I have bought and put together kit K8095 (MP3 player). Everythhing works, accept de LCD display. There is no fault in the PCB and all the components are ok (I’ve checked and double checked) I’ve consulted this forum, and did everything I could find on the matter. I find out that DB4 is not o Volt and RS has no power at all. More and more I came to the conclusion that the PIC isn’t working well. Question: Can I get the PIC reprogrammed or replaced bij Velleman??
(Sorry for my bad English)
Regards,
S.de Kat, the Netherlands
Here are the voltage values on the LCD connector J10 when the power is connected but no button pressed:
1 GND: 0V
2 +5V: 4.75V
3 CONTRAST: 0V
4 RS: 3.3V
5 R/W: 0V
6 E: 0V
7 DB4: 0V
8 DB5: 0V
9 DB6: 0V
10 DB7: 0V
11 LED_A: 11.7V
12 LED_K: 5.3V
Please check the RS pin (4) is not in short circuit to GND.
Here are the voltages I have on connector J10 (LCD mounted):
1 GND: 0V
2 +5V: 4.77V
3 CONTRAST: 0V
4 RS: 0V !!!
5 R/W: 0V
6 E: 0V
7 DB4: 0V
8 DB5: 0V
9 DB6: 0V
10 DB7: 0.48V !!!
11 LED_A: 11.44V
12 LED_K: 7.63V !!!
I checked the RS pin (4), it is not in short circuit to GND.
RS pin 4 is only connected to pin 24 of IC3.
DB7 is only connected to pin 28 of IC3
It seems that the backlight hasn’t got enough power.
Hopefully you can give me a diagnoses?
Now you may check if the LCD module is defective:
Turn the power supply off.
Disconnect the LCD module from the connector J10.
Then turn the power supply on.
Check the voltage on pin 24 and on pin 28 of IC3.
What voltage values do you get?
IC3
pin 24: o volt
pin 28: 1,71 volt
It seems that for some reason the card goes to “No LCD” mode.
In this mode there is no voltage on pin 24 of IC3 and pin 28 has some volts.
Is the LCD backlight on?
Do you see on the top line of the LCD dark squares when the contrast potentiometer is turned to max position clockwise?
If yes, then the card is in “No LCD” mode.
Yes I have some backlight (less power LCD pin 12 = 7.63V not 5.3V)
I see on the top line of the LCD dark squares when the contrast potentiometer is turned to 0 volt. They disappear when the position goes to max: = 1.73V
J8 has NO shunt!
For some reason the microcontroller’s internal pull-up resistor can’t pull pin 28 high enough.
This is the reason why the “No LCD” mode is detected.
You have now two alternative solutions to the problem:
- You can send the card to check/repair.
- Or you can solder a 1k resistor between terminals 2 and 4 of J8.
This resistor pulls the pin 28 high enough to detect there is no shunt on J8.
The backlight is driven by a constant current source (T1, R9). The voltage over the backlight LED may wary but the LED current is fixed 25mA.
I tried at once your suggestion to solder the resistor, but alas this didn’t solve the problem; nothing changed
in the situaties.
So I think we are at left with the other solution!
Were do I send the board to and also important what are the costs of check/repair??
Regards
Please return the card to:
Velleman Projects Tech. Dept.
Legen Heirweg 33
9890 Gavere
Belgium
Please include a copy of this conversation.
Please see also: velleman.eu/support/warranty … be&lang=nl
Daer Velleman,
On the first of march (01-03-2012) I 've send you my card for a check.
I haven’t heard from you since; neither did I get my card returned.
I’m curious to know the state of affairs.
With regards,
Steven de Kat, Haarlem, the Netherlands
Repair dept. informed us that your unit has been treated under warranty on 15/3/2012, so it should arrive soon.
Thank you Velleman!!!
This afternoon I received de card back and it is working fine!!!
Can you tell me what was wrong?.. So I can learn something from it?
Many recards and again thanks,
S. de Kat
Repair dept. informed us that the µ-controller has been replaced.
Again, many thanks.