My 8055 board works great with the test software. Than when I remove the Sk2 and SK3 jumpers and apply external voltage to the analog inputs it grounds out the external voltage source. I tried running a jumper from the internal voltage source back to the analog input and that worked. So why won’t it work with the external voltage?
Do you have a multimeter to check the external voltage between A1 terminal (or A2) and GND terminal?
The voltage to A1 or A2 must be positive compared to the GND terminal.
Turn the trimmer potentiometers ATT1 and ATT2 to max position clockwise.
Please check the resistors R3 and R4 are soldering.
Also check the analog input connector SK1 terminals are well soldered.
With the jumpers on the voltage is 5.06 volts at A1 And A2 0 volts with jumpers off. All sodering looks good. Here are the circuits I tried.
What is the voltage between terminals A1 and GND in the left drawing with text “Does not work”?
What is the voltage on the output tap of the external potentiometer if you disconnect it from A1 ?
With the Pot turned all the way:
5.06 between A1 and Gnd
5.06 at tap with A1 disconnected.
But when I connect the USB cable both drops to .07 volts.
It seems to short out with the cable connected.
It seems that the plus (+) pole of your power supply is grounded.
When connecting the minus (-) pole to the GND of the K8055 and having the USB cable connected, the minus pole of the power supply will be grounded too. This will short circuit your power supply.
You have to disconnect the plus (+) pole grounding of your power supply.
OK.
[quote]But when I connect the USB cable both drops to .07 volts.
It seems to short out with the cable connected.[/quote]It seems that the plus (+) pole of your power supply is connected to GND via an external loop.
This is the cause of the problem.
I have been using this power supply for a couple of months now with no other problems. I’ll just do some more testing and see if I can find the problem. Thank you for you help.
Ralph