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Paper feed problem HP Laserjet 4L

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Paper feed problem HP Laserjet 4L by cschade (2/14/10 4:49 PM) reply + / -
My old reliable LJ 4L started acting up after I replaced the cartridge. Paper started jamming more and more frequently at the entry to the toner cartridge. HP said take out the cartridge and replace it. I did, and it worked a few cycles then began jamming nearly every time.

Manual feed does not work. Same symptom. Paper stops at entry, paper jam light comes on.

Cleaned the rollers. Again, it worked a few times. Bought a second (low price) cartridge. Cleaned up the toner spill and got 8 good pages before the same thing happened again.

The symptoms are very similar to the ones described in the paper sensor arm replacement kit, EXCEPT the paper sensor arm is NOT broken off. The paper comes to rest on the arm.

I can get it to feed by pushing the reset button, but it doesn't print under those conditions--just flushes the paper out, reloads a new sheet, and jams again.

I am suspecting a sensor, and I haven't the foggiest idea how to get at it, even if I had the right test equipment (the manual suggests an oscilloscope would be needed to check the timing sequence).

Anyone have any ideas?

Thanks,

cps


Re: Paper feed problem HP Laserjet 4L by moe (2/14/10 6:54 PM) reply + / -
The low price cartridge part should be a clue. I've seen cartridges, particularly Staples brand, cause jams. I'm going to blame the toner cartridge based on the fact that the paper starts feeding ok temporarily when you change them. Those cartridges can damage the motor drive gear as well, causing it to split from the strain of driving the badly rebuilt piece of crap. You get what you pay for, the old adage goes.


Re: Re: Paper feed problem HP Laserjet 4L by cschade (2/15/10 7:14 PM) reply + / -
Sorry. I did not explain the problem carefully. The problem began when I put in a new HP cartridge (though they do not make them any longer). As I had already sent back the old cartridge to recycle, I needed a second one to confirm it was NOT the cartridge. That's when the low cost cartridge came in. It was only in the printer for about 15 minutes total, and did print a few pages. The HP cartridge actually did about the same.

In addition, the feed problem is the same with the cartridge out. I have defeated the top and back switches with tape, and I can watch the paper feed. It goes as far as the sensor arm and stops. The paper jam light goes on. Manual feed: same thing. It grabs the paper, advances it to the sensor arm, stops. Turns on the paper jam light.

Pushing the reset button flushes the paper out of the printer cleanly.

Perhaps that's a better explanation?

Thanks,

cps


Re: Paper feed problem HP Laserjet 4L by Anonymous (2/22/10 6:59 PM) reply + / -
Same happening to me since last week. The paper stops either righ at the roll or gets past the roll a bit and stops before it reaches the cartridge. The cartrige is the authentic HP, so no problem there. I am thinking about getting the replacement kit from here: http://www.fixyourownprinter.com/kits/HP/K29 but the sensor arm doen't look broken either. The arm is also sold for $10 online.
Any luck with your fixes?


Re: Paper feed problem HP Laserjet 4L by moe (2/22/10 8:24 PM) reply + / -
The paper wouldn't get that far if the arm was broken. If it doesn't look broken, why change it. Once it gets past the arm, the arm is no longer a possibility.


Re: Paper feed problem HP Laserjet 4L by cschade (2/23/10 6:05 PM) reply + / -
That's basically what mine is doing. The paper stops resting against the sensor arm.

Am I right to suspect a sensor or an electronics problem? It's odd, because I expect sensors to be all or nothing, and this problem has built up over the months starting when I replaced the cartridge the first time.

If it is a sensor, I haven't the foggiest idea how to test it.

Thanks,

cps




Re: Paper feed problem HP Laserjet 4L by moe (2/23/10 7:25 PM) reply + / -
Optical sensors never go bad. I've fixed a few by directing a blast of air from one of those air dusters with the long tube on them. You blow it down around the arm and in theory it will blow the dust blocking the optical sensor from seeing the arm.


Paper feed problem HP Laserjet 4L by cschade (2/24/10 6:23 PM) reply + / -
That was my theory, and I already tried a few puffs of air from a camera cleaning bulb. I'll get a can of compressed air and really zap it. Can't hurt, and the worsening symptoms over time are consistent with something gradually building up. Do spiders ever nest in printers?

Thanks,

cps


Re: Paper feed problem HP Laserjet 4L by moe (2/24/10 10:29 PM) reply + / -
Oh yeah. My favorite was some years ago when one electrocuted itself on the charge corona wire of a LaserJet III. The result was blank pages, since the HV was shorted out. Plucked the sucker off and it fixed it.


Re: Paper feed problem HP Laserjet 4L by Anonymous (2/26/10 4:19 PM) reply + / -
I can get the feed mechanism to work when I feed manually (with the cover off). After a sheet of paper gets to the roller I manually turn the roll a bit. It grabs the paper and pulls it all the way. I will try blowing the dust off too. Will let you know tomorrow if it helped.


Paper feed problem HP Laserjet 4L by cschade (2/26/10 5:34 PM) reply + / -
Well, I don't know about you, but I think I have a poltergeist. The air worked--or seemed to. For the first time in weeks, paper would feed past the sensor and through the rollers into the output. I put in the cartridge and successfully printed several test sheets.

I overlooked recent history.

All previous "fixes" (removing and replacing the cartridge, cleaning the rollers, using a different cartridge) have all "worked" but after a while the problem recurred. In this case, "after a while" was as soon as I hooked it up to my computer.

I hope you have greater success, but I am completely stumped. I would have given up on this months ago and thrown the printer away if it wasn't such a *good* printer. If anyone has any ideas, or knows a competent exorcist, I'm all ears.


Re: Paper feed problem HP Laserjet 4L by BNJ (3/12/10 8:16 PM) reply + / -
I just ordered a replacement cartridge. Next I removed the existing cartridge to shake it a bit. That's what I do to get a little more use out of the remaining toner.

Next, I put the cartridge back and to my great annoyance I have the same problem with the paper jaming in the front. What a great printer! Perhaps we should put it on Facebook. I might bury in the backyard along with the refurbished cartridge I just ordered!

I'm not giving up.Tomorrow off to Staples to buy some air.




Re: Paper feed problem HP Laserjet 4L by BNJ (3/12/10 8:24 PM) reply + / -
I just ordered a replacement cartridge. Next I removed the existing cartridge to shake it a bit. That what I do to get a little more use out of the remaining toner.

Next, I put the cartridge back and to my great annoyance I have the same problem with the paper jaming in the front. What a great printer! Perhaps we should put it on Facebook. I might bury in the backyard along with the refurbished cartridge I just ordered!

I'm not giving up.Tomorrow off to Staples to buy some air.




Re: Paper feed problem HP Laserjet 4L by Anonymous (3/15/10 4:18 PM) reply + / -
I had the same problem. I printed twice since I "fixed" the problem. I noticed a lot of fine white dust when I removed the cartridge on the left top inside of the printer. I used a pencil
eraser top and rubbed it of and blew it off as well. Seemed to correct the problem
I have owned this printer forever. I have been using remanufactured cartridges for years without any problems. About
40 bucks including shipping. Good luck.


Re: Paper feed problem HP Laserjet 4L by cschade (3/17/10 6:25 PM) reply + / -
Well the white powder idea was interesting, but that's not it. At least I don't have to worry about my printer getting anthrax. I am starting to suspect either (1) spider webs so dense that air won't blow them away (I just dug a bunch out of a bicycle pump, so I think this is a remote possibility) or (2) a failed light source for the sensor. I was told the sensors don't fail, but they must have a light source, which might. Does anyone know if the light source is infrared or visible light? If visible light, I might be able to test the printer in darkness, and see if I can see any light near the sensor arm. Or am I just stabbing in the dark?

Thanks,

cps


Paper feed problem HP Laserjet 4L by cschade (4/29/10 11:06 AM) reply + / -
Just as a follow-up. Since blowing air blindly at the sensor through the port for the paper detector arm did not work, I screwed my courage to the sticking place and used the service manual to disassemble the printer down to the DC board. The sensor appeared clean, when I found it, and it was not loose on the board. I can't rule out a cracked circuit board, which caused a similar intermittent problem in a radio I had years ago.

With no better idea, I blasted the sensor directly with compressed air, then reassembled the printer. To my surprise, I had no extra parts and only lost one screw (some readers will think that my perseverence is evidence I lost a lot more than one screw!).

To my utter amazement, it began to feed paper correctly. It worked the next day. And the next.

I don't know if it's actually fixed. I'm very suspicious of a loose component or microcrack in the board, which I will *never* find. Such things cause exactly the symptoms I have observed. Mess with something and it works for a little while. I may just be having a slightly longer mean time between failures. On the other hand, if it keeps working, the advice will be to blow air directly on the sensor assembly.

Stay tuned.


Re: Paper feed problem HP Laserjet 4L by moe (4/29/10 2:29 PM) reply + / -
A couple of people have fixed those boards with the infamous board baking technique popularized by this board. You need to remove the board from the plastic housing and remove the plastic cover over the HV power section. It wouldn't hurt to take the solenoid off the board either. 350-400 degrees for 8 minutes. That reflows all the solder. I'd wait until it broke again.


Paper feed problem HP Laserjet 4L by cschade (4/29/10 5:24 PM) reply + / -
Very clever. Appreciate the tip. And yes, I will wait until it breaks again. Taking anything that complicated apart makes me nervous, but I really like the workmanship that I see when I peel all those layers.

cps


Re: Paper feed problem HP Laserjet 4L by wjmciver (2/22/11 5:38 AM) reply + / -
Paper coming from the paper tray hangs on the upper left corner of the paper before entering theprinting process.


Re: Re: Paper feed problem HP Laserjet 4L by moe (2/22/11 9:21 AM) reply + / -
Remove the paper tray. In the upper left corner is a black plastic assembly held in by one screw. Remove it and clean it.


Re: Paper feed problem HP Laserjet 4L by Dick Parks (8/18/11 6:03 PM) reply + / -
I looked hard with a bright light and found a scrap of paper stuck in the feed just past the rollers - got it easy from the top with the cartridge out. Now I have a new printer and a spare!


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