Strippit  and  General Electric
Servo PWMC Comp Values
In the 1970's and 1980's,  before  Neutron Jack  Destroyed the  U.S. CNC Control Industry,
General Electric Co. was the World Leader in CNC Controls and Servo Drives.

These CNC Control & Servo Systems were Widely Used on Hundreds of Different Models of 
Lathes,  Mills,  Machining Centers,  and of Course,  Strippit Turret Punch Machines.  
The G.E.  Hi-Ack Model 2 and 3 Servo Drives Provided the Power for Machine Axis Motion Control.

These Machines had Great Variations in  Axis Speeds, Weight,  and Rigidity.   To Provide Machine Designers
a way to Compensate for these Variations,  G.E. Provided on  All  PWMC Servo Control Boards Terminals
where The Machine Designers Selected and Installed Unique Values of Several  Resistors,  Capacitors,  and 
Zener Diodes as a way to Taylor Servo Response of Each Individual Axis of each Type and Model Machine.

This Important Comp Value Information should be Provided in  Original Machine Manufactures
Schematics and Service Manuals,  and Copies of these Important and Unique Comps for Each Axis
should be Carefully Copied and Preserved!

Unfortunately,  Like  Egyptian Hieroglyphics,  the Knowledge that  All  PWMC Boards
Have to be Properly Configured with Correct Compensation Values,  and more Importantly 
What these Values Should be for Each Individual Axis on Each Machine,  is  Rapidly becoming Lost!

If the Wrong Comp Values are Installed on  PWMC Board,  or  "Double"  Comp Values Installed, 
the Machine Axis will  Position Poorly,  Over-Shoot,  Oscillate,  or  Not Position and Run at all.
Damage to  Power-Boards,  Power-Modules,  and Servo-Motors could also result.

When G.E. Built these Boards, 
G.E. Installed a Standard TEST-Set of Comp Valves Just for their Testing Procedures.
TEST Comp Component Values will  NOT  likely be Correct for Most Axis on Most Machines,
and usually will Need to Be Changed Per The Original Machine Manufacturers Specifications!

As I Sell and Repair PWMC Servo Boards,  I am Finding the Same Problems Over and Over Again
caused by Uninformed Technicians and Servicemen making Mistakes at their Shops and Factories.

  1  --  Swapping PWMC Boards  (Without Changing the Comp Values!)  Between Different Machine Axis, 
          or even Worse,  Between Different Machines,  Causing Multiple Problems on Multiple Axis and
          Perhaps Losing what the Correct Comp Values Are for All Axis on their Machines.

  2  --  Installing a New or Repaired Board from a Test Facility that has the Test-Comp Values Installed,
          but  Not the Correct Comps for this Particular Machine and Axis.

  3  --  Installing Incorrect Comp Values for a Particular Machine and Particular Axis,  by Perhaps,  Copying
          the Wrong Comp Values from Old Board and Installing the Same Wrong Comp Values on New Board.

  4  --  Installing New Comp Values Without Removing All the Old Test Comp Values so that you
          now have  "Double"  or  2 Sets of Comp Values Installed.

If you are having Servo Problems with  G.E.  Hi-Ack  Model 2  and  Model 3 Servo Drives,
I would Always Check that the  Comp Values are Correct on  Each-Axis for this  Particular-Machine!

General Electric  Model 2  PWMC3
  and  Model 2UL  PWMC4  Boards
PWMC3  Series was the First Type of  Model 2 Servo Control Boards.
First Version was  PWMC3,  but Boards were Continuously Improved over the Years  into Newer
PWMC3B,  PWMC3C,  PWMC3D,  PWMC3E,  PWMCF,  and Final Version  PWMC3G.

These Boards had 10 Screw-Terminals  (Except for  PWMC3F  which has 10 Solder-Posts)  where 
G.E. Test Comp Values  or  Customer's Machine Comp Values were Installed,  as Shown in Photos Below.

PWMC3  Servo Control Board Type
10 Screw-Terminals for Comp Values.

Boards has  2 Connectors  5PL  and  6PL.

PWMC3D,  PWMC3E,  and  PWMC3G.

There Photos are Not showing
Complete Circuit Boards,
but are Emphasizing the
Comp Parts Installation Area.
PWMC3F  had 10 Solder-Posts for Comp Values.

This was the First  "U.L." 
(Underwriters Laboratories)  Type Board
Developed for Increased Safety and Reliability.    PWMC3F  has a  3rd  Connector  16PL
where Board Received  D.C. Power.
U.L. Boards went into a  U.L. Servo Chassis.

G.E. Eventually Redesigned All Boards and Chassis into New  U.L. Types,  But
PWMC3F  and   New  U.L.  PWMC4  Boards were Virtually Identical and were simply Rehashed
Old PWMC3E Boards.

This Board could also be Used in Older
Non-U.L. Chassis by Soldering  4 Jumper Wires Across  8 Solder-Posts like the Photo at Right.
Board would then get it's D.C. Power from
5PL  and  6PL  like other Boards in the Series.
PWMC3 Series Boards  Left the G.E. Factory with Standard Test Comp Values Installed.
These Values were;      R1   2.2 M Ohm,       R2   47K Ohm,       R3   10 Ohm,       C5   .47MFD Capacitor.

PWMC4  UL Series Boards  Left the G.E. Factory with Slightly Different Test Comp Values Installed.
These Values were;      R1   2.2 M Ohm,       R2   68K Ohm,       R3   10 Ohm,       C5   .47MFD Capacitor.

At The Strippit Company,  These Test Comps were Engineered and Changed to Provide
Optimum Servo Drive Response for Each Axis on these High-Performance CNC Turret Punch Machines.
Following are a List of Comp Value Components used by Strippit on Machines with Model 2 Drives.

Machine Type               X-Axis                                     Y-Axis                                                     T-Axis
                                         R2      R3      C5      RL    CL      R2      R3      C5     RL     CL     Diode         R2      R3      C5    Diode
FC750  &  FC750/2     100K  100K   .22      --       --       100K   47K    .27      --       --          --             --         --        --        --

FC1000/1  30S/3                100K   47K    .22      --       --       100K   47K    .27      --       --          --             100K  47K    .33   1N5231  5.1V
FC1000/1  HC           100K   47K    .33      --       --       100K   47K    .27      --       --          --             100K  47K    1.0   1N5231  5.1V
FC1000/1  "A" Rev. D        100K   47K    .33      --       --       100K   47K    .27      --       --          --             100K  100K  1.0   1N5231  5.1V
FC1000/1  "A" Rev. F        100K  100K   .22      --       --       100K   100K   .27      --       --          --             100K  100K  .33       --

FC1000/2  HECC80/1         100K   47K    .22      --       --       100K   47K    .27     330    .022      --              100K   47K   .33       --

FC1250  51S/4  Y Size3     100K   47K   .27      --       --        100K   47K    .47      --       --          --              100K   47K   1.0       --
FC1250  "A"     Y Size4     100K   47K   .27      --       --        100K   47K    .47      --       --   1N5231  5.1V   100K   47K   1.0       --
FC1250  "A"     Y Size5     100K   47K   .27      --       --        100K   47K    .47      --       --   1N753B  6.2V   100K   47K   1.0       --

FC1250  HECC80/1            100K   47K    .27      --       --       100K   47K    .47    (330)  (.1)  1N753B  6.2V   100K   47K   1.0       --

FC1250/30/1500 H80/1       100K   47K    .1       --       --        100K    47K    .33      --       --   1N753B  6.2V  100K   47K   .33   1N5231  5.1V
   "  H80/1 33-ST. Laser     100K   56K    .1       --       --        100K    56K    .33      --       --   No Diode?      100K   75K   .33   NO DIODE?
   "   H80/306 33-ST.          100K   47K    .1       --       --        100K    47K    .33      --       --    No Diode?     100K   47K   .33   NO DIODE?

FC1500/45         (D.R.)        68K   100K   .33    220    .1       150K   31K     .27    (330)  (.022)     --              100K   47K   .33  (RL330  CL.022)
FC1500/45            2nd       100K  100K   .33    220    .1

Notes; ---  Zener-Diodes Provide Current Limiting to Protect Servo Drive and Servo Motor, lower Zener Voltage means lower Current
           ---  RL  and  CL  Parts  Provide High-Frequency Attenuation so that Axis does Not Oscillate and "Buzz".
           ---  RL  and  CL  Parts,  In  Brackets,  I added to Problem Machines to Cure High-Frequency Attenuation so that Axis does
                Not Oscillate and "Buzz".   The Point is that some Comps may Need to be Adjusted for some Machine's Axis to Run OK.
           ---  At Strippit Co.,  we Left the  R1  2.2M Ohm Resistor on  All  PWMC Boards,  Removed Other G.E. Comps Parts, 
                then Added Proper Comp Values for Machine and Axis Per the Chart Above.

PWMC7  and  PWMC8  Boards leave the
G.E. Factory with  7 Screw-Terminals, 
with  All the Screw-Terminals Left Empty.

The G.E. Test Comp Parts were Soldered Directly to Circuit Board,  so this made it
Very Easy for the  Uninformed to Add our Strippit Machine Comps to Screw-Terminals,  and now you have  "Double"  Comp Parts
on Board and your Machine would Not Run!
This is A Very Common Problem!!!

At Strippit,  we Left-On  R10  2.2M Ohm  and  C8  .1MFD,   but Carefully  Cut-Off 
R9,   R11,   R17,   and   C7,   then Added Our Replacement   R9,   R11,   R17,   and   C7
Comp Values to Proper Screw-Terminals.

On Strippit FC1000/3 Machines the Servo was Mounted on Punch Machine Frame and was Subject to Much Vibration.   So,  Instead of Using Screws,  we Removed Screw & Nut from Terminals,  and Soldered Our Comp Values Directly to Terminals for a Very
Secure Connection,  like in Photo at Right.
The  G.E. Hi-Ack Model 3  and  3A Servo Drives were Designed to be a Higher-Voltage  (150 Volt .D.C.)
and Higher Performance Servo Drive than the Older Model 2  (90 Volt D.C.)  Servo Drive System.

Early  Model 3 Drives used a  PWMC5  Board to Drive  2 Power-Modules
and  PWMC6  Board to Drive  4 Power-Modules for Higher-Current Capacity.

The Original Model 3 Drive was Not the Most Reliable,  so  G.E. Engineers Redesigned
all Circuit Boards and the Servo Chassis in to the Much Improved  Model 3A Servo Drive.

PWMC5  Board was Replaced by Improved  PWMC7 Board.
PWMC6  Board was Replaced by Improved  PWMC8 Board.
If you still have an Old  PWMC5  or  PWMC6  Board in your Model 3 Drive,
Throw It Away and Replace it with Improved  PWMC7  or  PWMC8  Board!!!

Early  U.L.  PWMC3F  and  PWMC4  Boards
were Redesigned into the
PWMC4A  and  PWMC4B  Servo Control Boards.

PWMC4A  and  PWMC4B  Boards were Very
Cleverly Redesigned to be Backwards Compatible with  All  U.L.  and  Non-U.L.  Chassis,
did Not Need or Have the 8 Solder-Posts,
and used  8 Screw-Terminals for the Same
Comp Values that used 10 Screw-Terminals
in older PWMC3 Boards.

So if Replacing a PWMC3 Board with a Newer PWMC4A  or  PWMC4B Board,  do Not Use Same Screw-Terminal Numbers as they have Changed.   Instead,  Use Comp Value Part Number Printed
on the Board.   Example,  on
PWMC3  Boards  R3 goes Between T5  and  T6,  But on 
PWMC4A  Boards  R3 goes Between T5  and  T1.
PWMC7  and  PWMC8  Boards
are Very Similar, 
Except the

PWMC7  Board Drives  2 Power-Modules

and the

PWMC8  Board Drives  4 Power-Modules
for Higher Current Requirements.

General Electric  Model 3  and  Model 3A
PWMC7  and  PWMC8  Boards

PWMC7  and  PWMC8 Boards  Left the G.E. Factory with Standard Test Comp Values Installed.
These Values were;     R1   2.2M Ohm,     R9   47K Ohm,     R11  1K Ohm,     R17   10 Ohm,
C7   .68MFD Capacitor,     C8   .1MFD Capacitor.

For Strippit  FC1000/3  and  FC1500/45  Machines,  we Left-On  R1  and  C8,  
Cut-Off    R9,   R11,   R17,   and  C7
then Added New Comp Value Parts Per the Chart Below.

  Machine             X-AXIS                                             Y-AXIS                                              T-Axis
                              R9       R11       R17      C7             R9       R11       R17      C7              R9       R11       R17       C7

  FC1000/3          120K   220       120K    .27 UF      120K   220       120K    .27 UF       120K   220       75K      1.0 UF

  FC1500/45        120K   220       120K    .27 UF      120K   220       120K    .27 UF       120K   220       75K      1.0 UF

Monarch Machining Centers,  Gidding & Lewis Horizontal Mills,  and  Warner & Swasey CNC Lathes  are
the only other Manufacturers I have seen,  Beside Strippit,  that also used Model 3 & 3A Type Servo Drives.
As Most of these Old machine Tool Companies are now out of Business,  Try to Find
Original Comp Values for your Machine in Your Schematics and Service manuals.

If your,  Non Strippit,  Machine Axis is Not Positioning Well,  and Original Comp Values have been "Lost",
Try to get them from Machine Original Manufacturer!

If Not Available,  a Smart Technician or Engineer will Need to
Read Set-Up Information in Correct G.E. Servo Manual and Experiment to Find Values that will
Allow Smooth Acceleration and Deceleration of Axis with No Overshoot or Oscillation.
You can use G.E. Test Comp Values as a Starting Point,  and use the Strippit Machine Values as Real-World Examples Selected by Real Electronics Engineers.    On Strippit's,  X  Values were for Light  X  Axis,  and
Y  Values were Selected for Heavy  Y  Axis.   Adjust Valves Carefully until you achieve Performance you need.

I have Worked on some of these Other Brand Machines,  and have been Amazed at how Poorly the Servo System was Integrated with Poorly Chosen Comp Values on  PWMC Boards,  and Improper Handling of
Servo Inhibits and Contactors.   It's hard to Explain to Customer that His Machine was Poorly Engineered
and That's why they have Problems,  But I get the Retort   "Well,  it's Run Pretty Much OK for 25 Years".

I have come to Really Appreciate what Good Engineering was done at Strippit,  in the Old Days.

Nowadays,  with Most Real Engineers having Left Strippit,  Not So Much.

We Also have Small Stock of 
G.E. Hi-Ack Servo Drive Manuals For-Sale
if you have Lost Yours.

These come in 4 Types;
---  Model 2   
  ---  Model 2 UL
---  Model 3   
---  Model 3A 

You and Your Serviceman
Cannot Work on
Your Machine's Servo Drives
Without The Correct Manual!
This page was last updated: October 24, 2015
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Servo-Drive Web Pages Also!