Polar Mohr 76EM inaccurate measurments

Hello,
I have a Polar Mohr 76EM. Not sure the year but i know its been here for over 30 years. I am having problems with the measurement readings. For example - If i press 8 inches, sometimes it will be a 1/16 less or sometimes a 1/16 more. If i program a series of cuts, it doesn't go to the correct measurement.
Any suggestions?

 

Hi sir
Good day
I saw your problem
I would suggest very Strong that you measure first the Power Supply with a Good
DMM test:1) +9Vdc for IC tolerance 2.5% + - in the BR-Computer Board*BT1-R -2
2)+5Vdc IC TTL in the BR computer board BR1-2 3)+24 in the BoARD PS24 Vdc for Control Relais
4)+12Vdc for IC CMOS Circuit Board EI 5) -30Vdc IC for BOARD EI 6) +42Vdc for Solenoid Control,etc CU1 UNIT PIN 8-9
The tolerance is very Close + -2.5%
Use the Schematic Diagram in the CU-Unit

 

Hi sir
Good day
Did you fix it ?

 

I have a similar problem with the cutter being 1/16th short on cuts. Each time I start up the cutter the home position changes ( IE: 16.300, 16.202, 16.354 and so on ). When I set the cutter to 11" it is off ( short ) by 1/16th of an inch. But if I move the cutter to 10.75 it is accurate all the way to 30". If I move before the 10.75 without stopping at 10,75 the cutter is short 1/16th of an inch as well. But if I stop at 10.75 then move to 10,9,8,7,6.5.4.3 the positions are accurate. I cannot pre program the cutter for a series of cuts until this issue is resolved. I need the cutter to be accurates. So far I have tried

Removing the linear scale and removed the encoder, slid the plastics out opened it up ( glass is clean, no scratches ) cleaned the encoder glass with a qtip and checked all the bearings ( all are free ). Put it all back together and the same problem persists; it is out a sixteenth. I find it odd that when the cutter position is at 10.75 it is accurate from there and to 11”, 12”, 13” and so on. But when I bring the gauge forward below 10.75 it is off by a sixteenth. Yet if I stop at 10.75 then come below to 10,9,8” it is accurate.

I have also brought the back gauge into position from 10.5 – 11.0 with the hand wheel ( looking for skipping in the LED readout ) and the measurement is accurate which leads me to believe the encoder and scale are working properly.

I’ve changed the TAM board and endcoder cable. Problem still persists .

Any help appreciated

 

Good day Sir:
Hope you are well
Will be a Good Idea that you start Measuring the power supply:
Here is
DMM test:1) +9Vdc for IC tolerance 2.5% + - in the BR-Computer Board*BT1-R -2
2)+5Vdc IC TTL in the BR computer board BR1-2 3)+24 in the BoARD PS24 Vdc for Control Relais
4)+12Vdc for IC CMOS Circuit Board EI 5) -30Vdc IC for BOARD EI 6) +42Vdc for Solenoid Control,etc CU1 UNIT PIN 8-9
The tolerance is very Close + -2.5%
Use the Schematic Diagram in the CU-Unit
Remember the Power supply is the Heart in electronic, like The Heart is the Human being.
Any desviation of tolerance, Must be replace or Repair ir.
If all Supply are O.k
So follow this Steps:
TAM Board: LED VI ON or OFF backgauge Movement
LED V2 ON or OFF counting forward
LED V3 OFF will light up o.5seg while passing Reference Point.
The reference Point must be IN The label of the control box for Paper Cutter, when the machine arrive the REFERENCE POINT is determined by Factory, for the Reference Point.
Let me know any progress or question.

 

I don't suppose you have a wiring diagram for this machine in PDF? None came with it and need it before conducting testing.
The TAM board has a light that flashes red at 10.75 ( reference point?). But that is the only time it goes on. when I set the backgauge to 10.75 from there on it is accurate. But it MUST be set there.

Tam Board: LED VI OFF backgauge movement flashes red when it hits 10.75
Unsure of LED V2 or LED V3 location
There is a board called ML just below two switches. Acts as follows:
Using handwheel for positioning / Flashes 2 red lights when moving gauge backward then has 1 solid red and two flashing red when moved forward, top light shuts off when wheel moved forward
Using the +/- arrows on display unit: Top solid red light plus two flashing red lights when gauge moved backward, two top solid red lights plus 2 flashing red lights when moving forward. Unsure if this means anything but thought I would mention it. Cannot understand why cutter reaches 10,75 then is fine ..but if it is not set there. it is off 1/16th inch.