Raymond Mod II Control Boxes

Part I

The Raymond Black control box has been around for as long as I can remember. I began servicing solid state lift controls in 1975 and if my memory serves me correctly they were around back then. The Raymond control boxes have come in different shapes and colors containing separate control modules wired together within the main box. The older aluminum, Mod I, box contained black potted modules, sometimes a relay and a voltage regulator assembly. As the system improved it became a plastic box with three separate rebuildable control boards housed inside. Three different colors were used in the early days of the plastic style; blue, red and black. The rarely seen blue control box was an early 36 volt unit and carried the part number 154-005-220. A more common style was the red box which was for 24 volt operation and carried the part number 154-005-020. The red box is still widely seen today but most vendors have discontinued manufacturing the actual red enclosure so today you may find many red, or 24 volt control systems, housed within a black enclosure. Indeed the most widely seen and popular plastic style Raymond control is the 24/36 volt black box. Black box systems carry the part number 154-005-350. In this article we will be discussing this most popular of the control boxes and see it's upgrades and functions as they are today.

Housed within the main black plastic enclosure are the three control boards that electrically function as one unit. They all plug into connectors on the mother board which not only holds the boards in place but also makes the internal connections which electrically tie the three boards to the outside world and to each other. The three boards and their individual connectors are "keyed" so that they can only fit in the mother-board at the appropriate locations, idiot proof, so to speak. Let's separate those controls for a moment and see how their individual jobs relate to the overall system operation.

The AUXILIARY BOARD or AUX for short is one of the two larger boards within the control box. Each separate control has its own part number, the AUX board part number is 154-005-354. This control houses many functional operators including the directional logic circuitry. System directional contactors are energized through the AUX board via a directional driver SCR. Along with the directional logic you have checks for faults including shorted main SCRs and welded M contactor tips, Raymonds terminology for bypass or 1A speed is "M" speed. The fault detector also has a look-ahead circuit which will keep the directional contactors from energizing if a fault is found before contactors are closed. System maintenance and specific operation will be covered later. The M speed driver SCR is also within the AUX control board, along with suppression networks for both the directional and M speed contactor coils. M speed lockout is a function which holds off the M speed contactor if the main SCR doesn't pulse. This is used on many other systems as well, you can imagine the sever lurch you would encounter if the vehicle was not moving in SCR speed and then all of a sudden the M speed contactor closed putting the vehicle in full speed. This is obviously much needed safety feature. The only adjustment contained on this AUX control board is the M speed adjustment. Adjustment ranges are typical with other control systems, approximately 0 to 6 or 7 seconds.

The next large control board and I feel the beating heart of the entire system is the VARIABLE PULSE GENERATOR BOARD or VPG for short. This VPG control houses the main pulsing oscillator which generates the pulses used to fire the three large system SCRs. The oscillator, for those of you who are trivia buffs, is set up as a multivibrator type circuit, that is a particular style of oscillator arrangement. Accelerator control is accomplished via the VPG control board, by varying the frequency of this main oscillator circuit. All of the major control adjustments are located on this board of which two of these should not be adjusted without an oscilloscope. These two adjustments are the pulse width and overall frequency adjustments, miss adjustment of these controls could yield several unwanted operational failures. A chart showing all the control adjustments will be given later. The VPG control board has had the most revisions and upgrades of all the system boards, for this reason it carries several part numbers. The original and oldest part number is 154-005-227. This particular control board had problems due to the multiple 24/36 volt operating system. Raymond designed the regulator with two large dropping resistors which when operated on a 36 volt system would get extremely hot, to the point that they would discolor the circuit board itself. Raymond soon upgraded the VPG by adding another dropping resistor and a 24/36 volt selector switch. When the control was used for 24 volt operation the switch would short one of the resistors allowing only two dropping resistors to be used. On 36 volt operation systems the switch could be placed in the 36v position and all three dropping resistors would be used. This addition improved the heat dissipation significantly and the new upgraded part number became 154-005-357. One additional improvement was to use 1% resistors for all the resistors on the VPG control board. This 1% value relates to the resistor tolerance which means the value can only drift 1% from the value marked. In laymens terms it produced tighter control over all the various adjustments with very little drift once they are set. The newest part number that I am aware of is 154-008-300.

Finally the smallest control board in the black box is the POWER DRIVER BOARD or PD for short. The PD BOARD receives pulses generated by the VPG control, amplifies them and sends them out to each individual SCR on the system or traction panel. Most control systems have some sort of amplifier in order to increase the current necessary to fire the large SCRs. The most current PD Board part number is 154-005-363.

To electrically connect the three control boards within the control box the MOTHER-BOARD is used. As mentioned this MOTHER-BOARD contains the keyed connectors, and the electrical connections which run between the three control boards and connect them to the outside world. The connectors are keyed with a spacer which fits between pins 6 & 7 on the VPG and AUX boards. The red box also has keyed connectors and they are placed between pins 3 & 4, this way the control cards can not be interchanged between boxes. If you are familiar with the Raymond system you probably also noticed an AUTO/MAN switch located on the MOTHER-BOARD. This switch is the reset selector switch for the fault detector. When placed in the AUTO position the system will automatically reset itself after a fault has occurred. Lets say you have a condition which makes the vehicle lurch forward and drops out the directional contactors, in the AUTO mode the system will reset itself and what you will end up with is a contactor that seems to chatter pulling in and out constantly until you release the directional control lever. Under the same symptom in the MAN or manual reset mode the contactors will drop out and stay out until you recycle the key switch. Most of the systems I have encountered seem to be placed in the AUTO mode, which is fine as long as you do not allow the contactors to continue to chatter in a failure mode. This constant making and breaking will significantly reduce the life of the tips themselves. Typically located next to the AUTO/MAN switch is a control box fuse placed in the ground or battery negative path to protect the control box from high currents. Most boxes contain a 5 amp fuse but I have also seen 3 amp fuses used. One last item worth mentioning is the array of 16 system test points located at various points on the MOTHER-BOARD.

Next time we will give you some reference charts which show the various control adjustments and what each of the test points located on the MOTHER-BOARD are used for. We'll also discuss some features and give you some basic troubleshooting tips on the Raymond system. I would like to thank all of you that visited my new web site, we had an excellent response from our last NETWORK article. This article was suggested by Dick Falter at Falter's Quality Service, Thanks Dick. If you are ever surfing the web please stop by and say hello. I appreciate any and all ideas for test equipment or future articles. If you have a favorite forklift related web site, I would love to hear about it.

Raymond ModII: PART 2



Robert Meyers