Hello, I Put my K8055 board together, but when connecting to the pc, it’s not reconized, LED11 Lights up, but no other flashing LED…
What could be the problem? I checked every connection for 10 times now…
Any help will be appriciated!
Greets,
Lars
The lack of LED LD8 flashes indicates that the microcontroller IC3 is not starting to run.
If you have a digital voltmeter (DVM), please check from the pins of the IC3 that there is +5V on pin 1 and +5V on pin 20. Check also that pins 8 and 19 are connected to GND. If this is the case then you may try to measure if the crystal oscillator is running. You may measure the DC voltage on the pins 9 and 10. The voltage on those pins must be some volts between 0 and +5V (but not 0 or +5V).
Pin 10 has 5.02v, 9 is OK, pin 1 has 5v, but pin 20: 0v, pin 8 & 19 are connected to Ground. how do check if the crystal is running? i just have a multi meter.
thanks for the quick reply!!
Greets,
Lars
The microcontroller IC3 can’t run without the supply voltage on pin 20. There must be 5V.
Please check the trace coming to this pin from the USB connector. Especially check the narrow trace section under IC4.
Hi there, thanks for the reply!
I checked it all, resoldered all the connections, but still nothing on pin20…
what in earth could be going on here 
Greets,
Lars
If you look the thick trace going from pin 20 to the USB connector and if no break is visible you may check it with ohmmeter too.
If OK then check if there is connection from the bottom of the board to pin 20 of IC3. If not then the IC socket is faulty.
I’m sorry i counted from the top down for the right pins of the ic 
But from te bottom up, pin 20 has 5v and pin 19 is connected to ground.
So everything is ok i guess…
Or the ic is broken, or maybe the crystal…
But i don’t know how to check the crystal with only a dvm…
Thanks for your reply!
Greets,
Lars
OK. You may measure the voltage on pin 9 and pin 10.
In a working device pin 9 is about 2V and pin 10 about 2.5V DC.
This test just indicates that the crystal biasing is OK. It does not indicate if the crystal is faulty or not oscillating.
Please check the capacitors C4 and C5.
If everything OK - then you have to return for check/repair the PIC or the whole board.
pin 9 has 1.14V and pin 10 has 4.82v
C4 = 1.42v
C5 = 4.85v
there’s something wrong i think…
Yes, the voltages seem to differ from the typical values.
The reason to this kind of values indicates that there is some conducting material between pin 9 and GND.
BTW: Did you use normal soldering tin without any extra soldering flux?
All this indicates that there is something wrong with the oscillator of the microcontroller.
You got the oscillator running by connect the multimeter between the pins 9 and 10.
The multimeter’s voltage biased the oscillator circuit of the PIC microcontroller and the oscillator started to run.
You may measure the resistance between the pins 9 and 10. The resistance value should be about 1Mega ohm.
USB cable must be disconnected when measuring this resistance.
when checking the resistance between pin9 and pin10 and scale of my dvm set to the highest (2000k) it’s of the scale, when ik connect the two pins with each other, and measure quickly i see it rising… 500 700 1100 1500 1700 etc… till its of the scale…
this all while NOT connected with the usb.
This result and the other voltage measurement results indicate that the microcontroller is defective.
There seems to be no internal 1M ohm resistor between pins 9 and 10 as should be.
It seems that you have to return the microcontroller.
The final test to verify this is to solder 1Mega ohm resistor between the pins 9 and 10.
The card should start to work OK in this case.
Alright,
What’s the best way to do this?? by mail? in a envelope or something?
And to what adress?
Many thanks for the advice and help so far!!!
I’ll try to find an 1M Ohm resistor en solder these between the 2 pins.
Greets,
Lars
Never mind, sending the microcontroller, a 1m resistor did the job:D