Polar N78 PLUS reboots every time I try to cut

Hi guys,
Greeting to you all, as I`m new to this forum.

I really hope you can help me with my problem: every time I try to cut something the machine stops, display freezes and displays for few moments some lines over current image (looks like a shattered LCD display) and the machine reboots. Sometimes the knife is lowered, sometimes locks immediately after pressing the cutting buttons and, if I`m lucky, I can sometimes get a cut.

Extra info:

1. I noticed few weeks ago that when the light barrier was interrupted while cutting, the machine stopped the cutting (obviously) but when trying to resume the cutting it did the issue described above (reboot + manual knife winding)

2. Checks/actions conducted:
- excessive greasing (I thought it my be a greasing issue);
- replaced all the front fusses and checked the 3 fusses from transformers slot (F1-F3) - I didn't checked the voltages, as I`m not sure what should I do;
- checked the safety bolt if it is stuck and the arm moves; also checked the sensors distance to be 0.6-0.8 mm
- checked position and cleaned the carbon brushes from the main drive - as I notices some lag between pressing the cutting buttons and cut action start.

3. Other observations: after reboot, the machine asks to "wind knife manually" but when I switch it off, to do that knife winding, the building`s main fuse goes off - not every time, it did this like 2 times from 16-20 off switching.

I thank you all in advance for any kind of help,

Mada

 

Hi sir:

Hope you are well, after reading your Post

1) I very strong recommend you the power supply for the Polar 78 Plus:a) +8Vdc b) +24Vdc c)+25Vdc d) +5Vdc e) +45Vdc , all they have a LED´s in the board KAP. MUST BE LIT.!!!!
all the Voltages will be in tolerance with 0.7% up or down, otherwise, are Faulty.

2)You indicate that you adjust the sensor, however, the sensor can be faulty, they have a small LED, must be Lit ! otherwise is indicative that is faulty, of course, can be another reaso lack of voltage, see your schematic diagram and measure if there are Voltage in the terminals of sensors.

3) Lube the Safety bolt, with Graphite Pencil, ( this is little trick) but is very effective, of course measure if there are voltage a terminal of safety bolt, would be another reason to be faulty( winding reheating) NOT burning, is differente thing.

4) Finally clean carefully all Edge Connector for Boards( very well)!!!!!

Let me know, sincerely

Blessing

 

Hi,
Mr. Chock, thank you for your indications!

I`ve managed to take some measurements:
- 5V power supply - 5.00 V
- 24V power supply - 24.00V
- transformer 8V - 9.81V
- transformer 24V - 23.90V
- transformer 25V - 29.80V

...and conducted the operation you recommended:
- cleaned all the board and connectors of dust (there was no rust or other problems)
- checked all LEDs, and all of them seems to be OK - they were lit
- the safety bolt is working properly: no need for 'greasing', the LED from FKP board lights when machine tries to start the cut.


I`ve read another post https://www.colorprintingforum.com/threads/restarting-polar-n115-plus-when-cutting.20433/#post-72296
and you recommended to this guy to adjust the main transformer`s TAP.
It is this a suitable adjustment for my machine or should I try another approach?
I leave you some videos:

-
here I managed to get few cuts (the last ones since)

-
here is the actual problem

 

Hi sir

Yes you can do it, adjust the tap IN The main transformer

if you use the 380 Vac, and you get 400 , go to 420 and vice-versa

However if the Fluctuation of voltage is up to 15% , i recommend you installa stabilizer voltage from Polar, they sell very good Stabilizer Voltage for the Input machine

Blessing

 

However i did notice:

That you did test all Voltages for Vac, and NOT the power supply for Vdc.( one missing of out of tolerance the paper cutter will be trouble)

1) Transformer tr1 1) +8Vdc 2)+24Vdc 3)+25Vdc section G1 4) +5Vdc Section G2 5) +24Vdc

The tolerance must be in 0.7% up or down.

 

Hi,

Thank you for all the assistance and advices!

I managed to get a visit from a Polar Mohr technician and he solved the problem.
He thinks the problem was a loosen connector behind the board`s chassis (connector 52) - he also said that it didn`t appear loosen to him at first look.
He came to this conclusion after verifying, step by step, all the actions during a cut, isolating and testing every part/sensors involved during the tested "step" of cutting. He observed that after "safety bolt retraction" the actual power for the carbon brushes is cut and machine restarts. Removing and reattaching that connector, solved the problem.

Regarding the high voltages that the transformer outputs, he said that is not so concerning for this particularly model as there are some galvanic protection systems (I`m sorry if I`m not translating correctly, in movies they do not talk 'electronish' language )

Everyone was surprised the find such a weird cause, but doesn`t matter as long we can resume our work.

I wish you all well!

 

Hi sir:

Great job, but you miss my recommendation from i did send you my advise:!! 4) Finally clean carefully all Edge Connector for Boards( very well)!!!!! remember?? you said everything was good???

Troubleshooting, is Arts with High Skill for ID any problem, and Resolve.

since you said that tech from Polar indicated you : the problem was a loosen connector behind the board`s chassis (connector 52)

Blessing

 

Hi,
You were right!
Lesson learned, next time I will dig further and check each cable.
They probably wouldn't even realize it if they didn't start isolating every segment of the cut action (they had the wiring diagram), because nothing else would indicate a loose cable or connector.

Regards!

 

ok, sir

Carefully in the Future with any words

Blessing