HP F4180 stopped working please help troubleshoot

[flat-earther]

I was doing a large print job with my HP Deskjet F4180, and after about 50 pages the printer stopped in the middle of a page and the black ink light started flashing.
So I went to refill the black ink cartridge with a syringe, but found out it still had a lot of ink.

I tried to print a page again but every time it would print only a bit of the page and immediately stop with the black ink light flashing again.
I tried two other black ink cartridges, and the problem still endured, so I knew this problem had to be with the printer itself.

I ran HP Print and Scan Doctor on my computer and it said it found a problem(don't know what) and fixed it. But again, the problem didn't go away.

Then I removed the black cartridge and tried to print one page with only the color cartridge in the printer, and it successfully printed the entire page!

But then, without doing anything after that one successful page, all of a sudden, the printer stopped working. And since then when I turn the printer on, only the scanner moves during startup, but the print head or paper roller motors do not move, and all lights flash on the control panel, which I found in the HP manual means a ''fatal error'' condition.

I suspect something on the motherboard has broken, but I'm just a layman and not sure how to find it, so I will appreciate if anyone helps me troubleshoot this problem. Video of the problem: https://rumble.com/v6t892t-hp-deskje...r-problem.html

[flat-earther]

This printer has an external power supply which supplies the printer with 16VDC and 32VDC. I confirmed both voltages from the PSU are working.

I opened up the printer and visually inspecting it didn't find any obvious problem. See video: https://rumble.com/v6t8bld-hp-deskje...nspection.html
Looks like it would be a lot of work to remove the motherboard, it's on the bottom of the printer under everything else, I would have to disassemble almost everything to remove it.
There is some space to inspect part of the motherboard without disassembling everything.
I have a multimeter, from the components visible at this stage is there any I should test? or do I have to remove the motherboard?

Because I don't want to disassemble unless necessary because those ribbon cables design is very delicate, I removed the control panel's ribbon cable from the motherboard and when reinstalling it, it was almost impossible to push it back in because the ribbon cable bent and blue plastic tab on its end fell off, I tried to glue it with super glue but it detached when pushing it back and the cable bent again, very frustrating this connector design.
If I disconnect the ribbon cables I'm worried whether I will succeed in reconnecting them.

[stj]

what does it do with the waste ink?

[flat-earther]

what does it do with the waste ink?

What do you mean? It's not printing so it's not creating any waste ink.

[flat-earther]

I found a photo of similar motherboard online, I labeled the connectors, maybe it's helpful for anyone.

[flat-earther]

I have finally removed the motherboard.
I will attach photos of it.
Can anyone advise me how to troubleshoot it?

[flat-earther]

I plugged the power cable into the motherboard.

I found that the 32V from the cable gets through a mosfet and successfully gets to the print head connector(see photo), so looks to me that the motherboard is receiving the 32V normally.

But then I found another mosfet that receives the 16V to its center pin(see photo), but the 16V doesn't pass through the mosfet when I measure its output pin(see photo).
Could that be the problem, that the motherboard isn't receiving the 16V?
Is it a broken mosfet, or something not allowing the mosfet to turn on? or what's going on? I'm just a beginner so it's difficult for me to draw conclusions from all this.

[CapLeaker]

No. It’s a BJT.

[flat-earther]

No. It’s a BJT.

Alright thanks.

[flat-earther]

Can anyone suggest how else to troubleshoot this board?

[flat-earther]

Any suggestions on what to check on the board?

[flat-earther]

The 16V bipolar junction transistor is NPN, and the 32V transistor is PNP.
On both measuring in diode mode between base and emitter in one direction is about 0.6V and OL in the other direction.

[flat-earther]

oh no all my photos have disappeared from this thread.

I noticed that when powering the printer's motherboard this black 50V 10µF electrolytic capacitor I circled in red has 13.55V measuring across its pins, and if measuring from ground to its negative side 31.7V and from ground to its positive side 45.47V.

Is that normal? the power adapter provides 16V on one wire and 32V on the other to the motherboard, so where is the 45V coming from?

That capacitor is not connected to ground. the negative side of that capacitor is connected directly to the 32V BJT which is near the power input connector of the motherboard, and the positive side of the capacitor is connected to the SN104961PJP TI chip.

[flat-earther]

With power connected to the motherboard, this is the DC voltages I measured on the 16V NPN BJT, black lead was on a ground.
16V on collector, 0V on base and emitter.
What does it mean?

[flat-earther]

I removed this 10V 330uf capacitor to check its capacitance with my multimeter and it read 350uf so I soldered it back.

[flat-earther]

I removed this diode to measure it out of circuit in diode mode, it is 0.235V one way, OL the other way.
is that okay?

[flat-earther]

with the motherboard powered up there is a very faint buzzing sound coming from the board from the side of the board where the power input area is, I can't pinpoint which component is making the noise, I only hear it bringing it close to my ear.
does that mean anything?

[CapLeaker]

With power connected to the motherboard, this is the DC voltages I measured on the 16V NPN BJT, black lead was on a ground.
16V on collector, 0V on base and emitter.
What does it mean?

Probably the NPN is used as a switch. So you got power there ready to go, but there is nothing on the base of the NPN, so it sits there not getting turned on. There is probably nothing wrong with the board itself. I’d go for the print head, take it fully apart and clean it. That seems to help 50% of the time. There are some models that once you hit 25000 pages the print head seems like just to die or something. Why I don’t know. I just end up replacing the whole printer if cleaning the print head doesn’t help, since replacing the print head is about the same price than a new whole printer.

[flat-earther]

Probably the NPN is used as a switch. So you got power there ready to go, but there is nothing on the base of the NPN, so it sits there not getting turned on. There is probably nothing wrong with the board itself. I’d go for the print head, take it fully apart and clean it. That seems to help 50% of the time. There are some models that once you hit 25000 pages the print head seems like just to die or something. Why I don’t know. I just end up replacing the whole printer if cleaning the print head doesn’t help, since replacing the print head is about the same price than a new whole printer.

With this printer design the cartridges are the print head.
I cleaned the cartridges and their contacts on the printer already before disassembling the printer, I also tried other cartridges which made no difference.
That's why I think there's a problem on the motherboard, or the print head board that the cartridges connect to.

I have now removed all electrolytic caps on the motherboard to check their capacitance to rule them out, and they all measured close to their value apart from the largest cap which is 50V 330uF and measured 316uF but I assume that's still okay so I returned it.


I destroyed a small 4V 220uF cap near the 16MHz crystal by pulling its leg out, I put a 25V 220uF cap that I had to replace it. I still measured it though by jamming a needle in the empty leg hole and it measured 242uF so it was fine.


I think I will remove the print head circuit board next to remove the three electrolytic caps on it to check them as well.

[flat-earther]

print head board photos
2004-HPDC
C9050-60037
CC47200PTJG
ELCN A.18
C9050-80003-54