T1200 MFP printer/scanner question

[D Hook]

Went back to the KISS method (Keep It Simple Stupid).

The original tech who worked on the printer told us he replaced the encoder wheel so I've not been looking at that as the problem.

Figured there wasn't anything to lose at this point. Took a moist paper towel and held it on the encoder wheel as it rotated to clean it.

Problem solved. No skips, no unusual ink placement on the rendering when printed in solid color. Everything is working as it should.

There is much rejoicing!

Learned a TON on this little project. Just wish it wasn't such an expensive lesson!

Thanks to all who chimed in and hopefully this will help others down the road.

[Kiran Otter]

I thought it was the encoder and/or disc all along. I'm glad you tried cleaning it first! Thanks for the update.

The fact they replaced the motor.... when all it that was wrong was the encoder disc was dirty...

Kiran

[D Hook]

Yep, you were absolutely correct on your diagnosis. NICE JOB! And thanks for the support. Really helped. I was ready to give up on this thing yesterday but just couldn't let it go. So I reread the thread and saw your response about suspecting the encoder disc and kept thinking "But they replaced that". But they didn't clean it after replacing (assuming they replaced it) so kept dismissing that as a problem. But there you go. Always the simple (cheap) stuff to try first.

*EDIT* Heard from another gentleman who said he had the same problem once. He accidently got grease from the gears smeared on the encoder disc. The grease is clear so it's not easy to see.

Now I just have to source a lower roll cover to replace one that has a broken hinge. Looking for used but not too common so might take some time.

Thanks again Kiran.

[D Hook]

New wrinkle in this repair saga.

Boss went to print a drawing today and got an 81:01 error. After rebooting the printer and selecting the same print from the list of drawings on the printer, we reprinted and it came out just fine. He said it's been throwing that error code almost daily.

So I did a Paper Drive test. Not sure how to interpret the results though. Also got a "WARNING: HIGH FRICTION" message on the display just before it gave a readout for the PWM. Here's the results:

PWM AVG: 8475.66 / 8477.13
Speed Error: 159.75 / 31.75
PWM ST DEV: 56.61 / 42.62
PWM MAX: 8632.00 / 8680.00

Looked in the service manual but not much info there as to what the results should look like.

The high friction warning was concerning but not sure what that applies to. I assume it means something is dragging. Paper feed maybe?

What does the PWM mean?
What does PWM ST DEV refer to?

Is this a sign the motor needs replacing?

After rebooting the printer, the next print comes out just as it should.

Thanks for any light you might shed on this.

[Kiran Otter]

Maybe it's your copy of the service manual, but mine has what the results should be like:

The PWM avg results must be between 16000 and 14000.
The Speed error results must be less than 50.
The PWM StDev results must be between 0 and 500.
The PWM max results must be between 15000 and 20000.

Was this the printer where the motor was replaced? If so they might not have installed it correctly. There's a specific tool for positioning the assembly during installtion and it's rather critical that it be in the right position otherwise the gears bind and you end up with too much friction. If the motor has not been replaced, I would make sure it's not something else in the path; labels wrapped around the friction roller or something jammed up underneath. It's very rare to have to replace the paper axis motor, but if this printer has excessive use, that maybe what needs to happen.

PWM stands for pulse-width modulation. The 'StDev' is the standard deviation.

Kiran

[Kiran Otter]

Something you might try, is eliminate the overdrive from the paper advance; remove one of the two larger white gears between the paper advance the the overdrive/starwheel area. Run the test again and see if anything changes. I'm attaching a picture with one of the gears removed.

2018-05-22 10.47.17.jpg

You have to remove the electronics module and spittoon.

Kiran

[D Hook]

When I was working on it earlier, I removed one of the white gears just to eliminate it as a possible cause of the skipping problem. It didn't have an effect on the skipping but I'll remove it again and make sure it's not a contributing factor to this problem.

Yes, the motor was included as part of the media advance transmission so all that is new. They did have the alignment tool when they installed the new part. Whether or not they used it I don't know.

Cleaning the encoder wheel solved the skipping problem but now I'm wondering if I should clean the sensors the encoder wheel travels between, in case there's some grease or something smeared on the sensor.

Thanks for all the info on the PWM readings. I'll take another look at the service manual. If the numbers I'm getting from the test are too low or too high, what does that mean?

As usual, thanks for the help!

[Kiran Otter]

Based on the warning and the numbers, I'd say there's something causing the roller/motor to turn with excess friction/stress. If you have the tool, I would repeat the process for installing the motor, make sure it's done correctly.

If it's printing correctly otherwise, I wouldn't bother trying to clean the encoder sensor. If it was fouled, you'd have errors galore.

Kiran

[D Hook]

Quick question: After I remove the encoder disk, do I need to replace with a new one or can I reuse the old?

[Kiran Otter]

You can reuse it assuming it still sticks well.

Kiran