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Get help with Large Format Printers, with direct access to all Latex Knowledge Center · Ask anything · Find anything · Share anything at HP LKC
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Designjet Z61

Hello all,

  We have a DesignJet Z6100 42" printer. Error code is 79:04. All buttons on front are unresponsive.  After taking the back off the unit, we have noticed there are 5 small green LED's on the main board to the right of the power supply. These LED's indicate that the voltages are present.


  We have 3 LED's on, and 2 LED's are off. The 24Volt and the V2Power (42V) LED's are off. We suspected the power supply was bad, and failing to turn on the 24V & 42V outputs.  We have removed all the ink cartridges, and all the print heads looking for something that may be dragging down the power supply for those two voltages.  This didn't help, and to that end, we have disconnected nearly everything we could find hoping to isolate what it is that is stopping the 24V & 42V supplies from starting.   Fairly certain we have removed all external possibilities, we elected to buy a replacement power supply.  I thought it was new, but it turns out it was "REFURBISHED" which means used, and cleaned with an air hose.


  The new refurbished power supply  has the exact same problem, no 24V & 42V outputs.  Could be a common problem for the 42" Z6100 plotter?  -OR- Did we just get a bad replacement power supply, or is there something else?



We have considered that maybe the z6100 doesn't turn on the 24V & 42V supplies until after some point in the boot up process.  If this is the case, then Maybe the supply is good, and there is a firmware type issue stopping the printer from booting up, and then finally turning on the supply outputs for 24V & 42V.   This is a guess, as we do not know what the printer was supposed to do, normally.


Can anyone answer with 100% certainty, that all 5 of the green LED's come on immediately, with the main power switch, or is there a delay for these two outputs?   I don't want to buy another power supply, only to find out the system has a delay, and we are wrong about the led's all coming on right at power up.










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Hello Everyone.


Just wanted to report back that the new hard drive that was formatted in HP format, and preloaded with the latest firmware, did in fact solve my problem.


Printer is up and running!


Also, I want to confirm that the 24V and 42V power outputs do come on later in the boot sequence.

They do not come on right away with the power switch.


Thanks to everyone who helped sort out this mess.




View solution in original post

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Here's a link to the service manual:




Talks about LED's start on page 14.

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  Thanks for the link. I found my answer on page 16. The 24V and 42V outputs do not come on until after some point in the boot process.  This doesn't solve my problem, however, but it did cut it in half.


So now I have a constant 79-04 error, that keeps repeating every time it boots.  It has been rebooted many times, and the error will not clear. Reading through the manual, I see that this most likely is a firmware error, and now I am pretty certain it is not the power supply, so I want to focus my efforts on re-installing the firmware.


HOWEVER, it WILL NOT boot into diagnostic or service mode. As mentioned before, the buttons on front panel are un responsive. We have tried many times holding the cancel and either the down or up keys, while turning the unit on in hopes to enter service mode.


Can you point me in a different direction?






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Let me add some more information.


Most of the time when you boot it up, I get this error:


X  79-04

Restart the printer, If the problem persest, call HP support




If you press and hold many/all buttons, clicking and pushing while it is booting, we managed to get to this screen, but only twice:


x 79-04


Code: oxbabeface

Severity:  Error

Priority :  3000

Id:  0x101021a



File:  Nvmphysfile.cpp



Maybe there is another clue in this error?





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I've found that I have to hold the three key combination (ON, CANCEL and DOWN [or UP} keys) until you see the screen come up showing a countdown from 30 before releasing the three keys.


I usually hold CANCEL and DOWN, then press and hold ON.  Hold all three until the countdown begins, then release all three.  That's the only way I've been able to get to the diagnostics pages.  I think the service manual says to release after 5 seconds or so but I could never get that to work.   It just kept rebooting the printer instead.


Are you connected to the printer where you can access the WebAccess feature?  I don't know how else to load the firmware without being connected to the WebAccess screen.


There's people on this board who have much more experience with this model.  I've only worked on a Z6100 once to do a belt change and it went without any trouble.   I'm working on a 4500PS that is similar to the Z6100 but that's about it.  Hopefully David Zuts or Mike will pick up on this thread and offer some other advice to trouble shoot.  Those guys do it for a living; I just do it to stay out of my wife's hair.  🙂

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  Thanks for  your suggestion.  I just tried to hold the buttons until the HP countdown screen appears. It is a long time, and hurts the fingers to hold it that long. I tried twice now, and still it will not let me into the diagnostic screens.  I will keep trying, maybe I will get lucky?


Yes, I have the printer plugged into an ethernet switch. I have my laptop plugged into the same switch.  Nothing else is on the switch, so it is a simple home network.  I am trying to get windows to "see" the printer in the network, but it cannot find it.  The lights on the NIC port on the motherboard for the printer are both lit, and you can see the ocasional flicker of traffic on the indicator lights on the switch, but still windows cannot find the printer.


Do you know the default IP address?  We have pulled the battery for CMOS clear, and have hit the recessed RESET switch on the front panel a few times.  I am pretty sure the last known IP address is not valid. 




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You can look at this thread and see how I connected (finally) my 4500PS directly to my laptop with some aide from DavidZuts:




Got it working okay.


I don't know if there is a default IP address.  I guess I'd still try the last known first.  Maybe they show a default address in the service manual?


You may want to get someone to help hold the buttons down if it gets too uncomfortable.

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  So I went and read through the post you linked to me. That conversation got me thinking about how I would find out the IP address of my printer when it is unknown.  Some more googling turned up a program called WIRESHARK. I downloaded this program, and ran it. 


WireShark was able to find the MAC address of the printer 3C:A8:2A:83:B1:7A

WireShark was also able to find the IP address of the printer.


With this information, I ran a command prompt, and pinged the IP address.

I got a 4 returned packets, 100% with no loss.


Thinking I was almost there, I opened a web browser, and typed

I got the message that this page cannot be displayed.


So now I am thinking the embedded web server(EWS) is gone, just like the firmware is gone. That makes since because I cannot get to the diagnostic pages, no matter how many times we have tried, and no matter how long we hold the buttons on the front panel down while booting.


Any additional ideas will be greatly appreciated.










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Can someone please point me in the direction of the correct "PLT" file for the Z6100 Printer?


I am able to connect to the printer, through a command prompt, and I am at the FTP prompt where the next thing it is looking for is the command


put "filename.ptl" <enter>



I have been searching the web, looking for the firmware file, and found that, but it is not a "plt" file.




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Plt or ptl?  You've typed both.

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