Internet PLC Forum

General => Technical support => Topic started by: dan on October 13, 2004, 03:36:36 PM

Title: Output
Post by: dan on October 13, 2004, 03:36:36 PM

Hi,

On a 2424 PLC one of the output is activated-LED on, but I have no voltage. I replaced the TPIC6A595 but with no succes. All other outputs are working Ok.


All the  outputs (includig one in question) are driving  24V relays.(Omron MY4)

Please let me know

Dan

Title: Re:Output
Post by: support on October 17, 2004, 10:39:10 PM

Which output? Some outputs are driven by ULN2003A or ULN2803A. Some are driven by TPIC6A595. The output driver must be damaged. If it is ULN2003A or ULN2803A it is quie easy to buy them off the shelve from any electronic component supplier. TPIC6A595NE can be obtained from us if it is damaged.

Title: Re:Output
Post by: dan on October 18, 2004, 10:23:24 AM

Hi,

Is output #13.
Like I said I  allready  changed the TPIC6A595 (I had some extra unused outputs) but I had the same problem and only on that output. The LED is comming on but no power on the output.

For know I changed the output to an unused one, looks ok, but definetly I like to know what is going on.

Please advice

Dan

Title: Re:Output
Post by: support on October 19, 2004, 04:56:51 AM

Output #13 is controlled by TPIC6A595NE but did you replace the correct IC? This output is controlled by IC UO4. The output is normal pulled up to the 24V power supply via the resistor network RU4 and the red LED. When the output is OFF you measures approximately 22V (due to voltage drop across the LED) but when the output is ON you measure 0V. When you said there is no voltage on the output do you mean you measure 0V? That means the output is ON.

Are you able to do an online monitoring to determine if the PLC program actually turns on this output? Did you remove the output screw terminal for outputs 9-16 to see if the LED is still ON? If so it is the wiring issue.

You can swap the IC UO4 with UO5 and see if the problem shifts to output #21. If so it is the IC driver that is blown.

If the problem still persist, you can remove IC UO4 and then power ON the PLC to check whether output #13 is still ON. If so then there is some stray short circuit on the trace. Remove the board from the panel and test it on your desktop to determine if there is any external stray short circuit due to installation.

If this can't be resolved, then please contacts sales@tri-plc.com to get an RMA # and send back to us for inspection/repair or replacement.