Minolta Magicolor 3100 ... Printer sayes its online and ready to print. When i send a print job it spools it ok but when it goes to print it goes offline. I delete the print job and the printer is back online.

Replace the Black image unit. Do the other colors print ok?

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

as i was printing on bizhub 450,the machine just stop to print.i checked the network connection,is ok. how can i solve this problem

check system on the computer may be problem in the printer or the computer isn't sending a signal through to the printer

I have a Konica user guide for your printer here:
2400w User guide PDF

Have a look at the introduction and troubleshoot sections for the light blink codes, these give you an idea if it could be an error.

This is likely a problem with the printer driver or the printer spooling system on your computer. Check in folder "C:\Windows\System32\spool\PRINTERS". If there are files in this folder at any time when you are not expecting a printout and there were no system messages, then it is confirmed.

The easiest thing to try is to uninstall and reinstall your printer drivers. If that does not do the trick and a problem with the printer spooling system, you might be able to try uninstalling and reinstalling this feature. If this does not work or you cannot do figure out how to do it yourself, you will need a Windows expert to fix it for you.

spooling, is where the information being sent to the printer is being checked/converted for the printer driver , prior to being printed

Start the Konica Minolta Status application and check the error, you should get more info there.

Reset your Toners and Imaging units for Bizhub and CF series.
http://www.chipreset.eu

Try to clear all the waiting jobs, a printer keeps the undone jobs in memory, Sometime that can cause you problems like that, The printer waiting and waiting and waiting.
Rightclick on the printer icon
open it
check for printerjobs in the queue..if there are any.

Good lyck to you

Have you tried a different port?
This will identify if it is a USB issue, possible USB 1 or 2.
It sounds like an issue with your port and not the printer, do you have access to advanced settings on your computer for USB?

I've had that problem before too, and found out that there were copies of the printer that had somehow installed themselves on my computer. All I needed to do was to choose to print with "konica minolta copy 1" instead of the one that I *thought* was installed and it worked. I then deleted the original printer and just stuck with the copy.