I'm trying to set-up an S7-300 CPU for educational purposes.

I purchased two CPU's on e-bay for a PLC educational project.

We have applied 24 volt supply.

All lights come on (no blinking).  The BUSF light says on RED.

MEMReset does not work.  

Holding it in CCW direction for 10 seconds results in NO blinking stop led.

Can not connect with a USB/MPI cable with Step-7 Lite (connection can not be made)

I attached an image of the box.  LED's never blink no matter what.

Any advice or suggestions are appreciated.

Hello,

try to remove the Memory Card and then Power on the System.

This LED Status normaly displayed if a internal SW Fault occurs.

Regards

Christoph

Hello,

this status isn't critical for my opinion, This looks like there is program with probably some distributed configuration on that MemoryCard. Simply create your own new prj, download it to MC and everythink will be ok. Give response.

Hello,

It is strange you don't have connection with CPU using MPI. Are you sure in your PG/PC Interface settings?

Best regards,

Hristo Mihalev

 Hello,

 Also remember that with STEP 7 Lite and your CPU 315-2DP the Profibus network will not work

 MPI port to the left

Even when I remove the memory, all the lights remain as shown.  Including when I use the MEMR.

I have not been able to connect via MPI using S7 Lite.

Hello,

hmmm sry for question again, when you put key to STOP then RUN, nothing change on that lights, maybe for a short moment? If yes, that's looks the CPU is faulty, because  key position change (STOP/RUN/FORCE) must change CPU LED status.

GCAPilot

Even when I remove the memory, all the lights remain as shown.  Including when I use the MEMR.

I have not been able to connect via MPI using S7 Lite.

 Hello,

  At power of the CPU has this behavior , if your power supply is correct your CPU is to be repaired

GCAPilot

I am using a very well regulated 24 volt power supply.  When I turn it on, all the lights just come on as in the image (steady - no blinking).  When I turn the MRES and hold it, there is no change at all.

I purchased one of these units on eBay and when I informed the seller I thought it was defective, they sent another.  They BOTH act the same way.

I just wanted to be sure these are indications of a bad CPU before I return both units.

Thanks for you help everybody!  

I'll have to look for another CPU of some sort for our educational project :)

Rob Rice

 Dear Rob,

 in these old CPU as well as the new , when you turn on the power for a few seconds all the LEDs are on steady then make their behavior , then hmmm , I lhave one old CPU  like you, tomorrow I will do some testing for you .

GCAPilot

Because I am unable to create an MPI connection to the CPU, I can not change the program on the memory card.

   Hello, have you tried with accessible node on STEP 7? Nothing? 

Hello GCAPilot,

It's all morning with CPU 315 2-DP (6ES7 315-2AF03) I think like yours, I try to do the LEDs steady, like removing the EEPROM with power on power off, remove and restore power quickly, but I can not, every time at power leds are steady and then go off and the CPU is started, it is really strange that both CPUs you have to have the same behavior, if you are sure of your power supply is correct (excessive ripple maybe) or bad ground connection, it is possible that your CPU is defective, as I said, strange 2 of 2  

Thanks for the reply.  I purchased another CPU on eBay hoping to get lucky - but:

If I take out the memory card ( or even if I don't ) then power it up, all the lights blink once for a fraction of sec and then go out.

If I hold the switch to MRES and the to run - NO lights come on at all.

I wonder if I have the power connected correctly - I am using a regulated 24V power supply with the positive lead connected to L+ and the negative to M.  The CPU is not connected to the rack.  Would that have any impact?

I appreciate your help.  I could just be buying broken junk on ebay :(

Hello,

how much Ampers can give that power supply? Find specification pdf for that CPU current consumption, compare with your power supply if it can give sufficient current to CPU. If CPU isn't on rack it's not problem. Can you be sure about measure that power supply voltage with multimeter, showing 24V +/- ?

Edit2: Typically my S7-313C working alone with my 24V-1A power supply normally.

GCAPilot

I am using a very well regulated 24 volt power supply.  When I turn it on, all the lights just come on as in the image (steady - no blinking).  When I turn the MRES and hold it, there is no change at all.

 Hello,

Either you have wrong power supply or change distributor (eBay) , buy from SIEMENS?

GCAPilot

Thanks for the reply.  I purchased another CPU on eBay hoping to get lucky - but:

If I take out the memory card ( or even if I don't ) then power it up, all the lights blink once for a fraction of sec and then go out.

If I hold the switch to MRES and the to run - NO lights come on at all.

I wonder if I have the power connected correctly - I am using a regulated 24V power supply with the positive lead connected to L+ and the negative to M.  The CPU is not connected to the rack.  Would that have any impact?

I appreciate your help.  I could just be buying broken junk on ebay :(

Hello,

 I think is this CPU in this thread that you have purchased right? 

 https://support.industry.siemens.com/tf/ec/en/posts/s7-300-312-cpu-all-leds-blink-briefly-then-out/138552/?page=0&pageSize=10

 3 CPU that not function is very strange, you can tell us your power supply? Some code?

GCAPilot

I made a dumb mistake with my power supply - it was only producing 12 volts.  The scale on its face is marked with V/A and I was reading the amp scale.  My mistake.

 Hello,

 You say that there was a problem with the power supply? 

 Now function?

GCAPilot

marked with V/A and I was reading the amp scale.

 Hey

 The CPU function only with 24 VDC direct current not alternating!!!!!!

Hello,

this can happen to everyone  shame that you've probably lost so much time with transfers trouble. Ok, have a good time with Siemens automation.