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Sir nyckuk . . . . . . .
I'm gonna throw a couple of facts on that unit towards you, to see if it is helping your understanding of it.
First, being the very easiest, is your not fully grasping the 2 wire versus 3 wire versus . . . . .even that 5 wire that some models are throwing at you.
Look at the blown up drawing just below and that will Edd-i-cate you on what's really going on, mechanically and electrically, hidden within that controls housing.
This above depiction is being of the REAR of the control.
So you now think and relate . . . . . .if my knob is being at extreme CCW, I have no motor speed or it is being very slow, now as I turn my knob to the right, the motor speed increases until I reach the maximum CW position where it is R E A L L L L Y running.
Then you look at the units PCB and see that at one corner , there is only being a fine blue and red wire.
Those would be going to that potentiometer. (Hey! spel chek duzzent knows . . potentially . . -.ometer ?)
Now if you will look at the potentiometer you can see that there could be two inter related values of resistance.
One between A to B and another between B to C, at center position, halfway, the resistances should be equal at a certain point.
As you move off from center , one resistance value increases while the other decreases, or conversely if you switch to the other direction.
When that interrelated action is needed, we call that a potentiometric function and A B and C connections are all being needed and connected up.
In your units situation, the circuitry that those Blu and Red wires are being connected to . .. . . they only want to see a change in resistance value.
They want a HIGH resistance value at LOW motor speed and a LOW resistance value at HIGH motor speed.
So you now look at the BACK of that control, using its illustration, and think about the knob on the front on the shaft, and think if I rotate the knob to its far CCW position that would put B connections wiper contact right up against C with almost no resistance between the two.
But it has left a highest possible resistance between B and A.
Soooooooo if I connect one of my two wires to A and the other to B, I have accomplished my need for HIGH resistance at a MAX CCW knob position and a decreasing to LOW resistance at MAX CW knob position.
When three connections are needed to that control it is usually called a potentiometric action.
In your case, of using only the wiper and one end connection, you are using it as a variable resistor and is usually called a rheostat action.
That explains your need for only 2 wires on your unit, and if you find use of 5 wires , you could expect three wires related to the control and two wires related to an added on on-off switch, activated at max CCW position , OR by a shaft activated push action switch.
Hey ! . . . . .I have to stop and ask . . .whats a Trolley . . .is it akin to a model railroad setup, but with use of only a trolley car?
Disregard . . .by the first word of the post, I see the word golf, so it must be the motorizing of a golf clubs carrier ?
So what I am doing now, is looking at your Fottie-Graf # 705 and figuring that this unit is being about 8 years old . . .right ?
(But it might have been on a store shelf . . . . .for awhile . . . . before you bought it .)
Look at center board and find D4 symbolized diode and below it you will find one HEALTHY solder connection.
Go up again and pass D4 diode and find an oval solder connection to the left, with part of its covered terminal peeking out, this connection looks OK also.
Look just to its right and see that solder blob and confirm if there is any possibility that the solder terminal in the center of that blob might have "arced out" and is just floating inside and not actually making connection ?
Question:
You say that the unit "hums" when you are advancing the speed control. Listen again and confirm if that hum increases UPWARDS in frequency as you advance the speed control clockwise ?.
Observation:
With you mentioning that the unit, when operating normally, will let you use the control to bring the speed up to almost its top adjustable speed, and then a relay kicks in to give maximum speed.
I believe that prior defined action is being a voltage level / threshold related function and that aspect is still operating as it always did .
The PRINCIPAL component on the speed control, relating to electronic control will be the black power device by itself at the right bottom corner.
Of a bit less importance, are the Q2 + Q ? Power pair up at the top that are receiving drive from Q4 and Q5 transistors over to their left.
The brains of the control circuitry, are the 8 pin IC's U4 and U3 over at center left.
For me to make any further analysis, I would need all of the marked numbers on those 5 principle devices.
It would be pity for your junking of this unit due to a blob of solder or a bad $4 power transistor fault.
Now . . . . . In standby mode . . .beep . . . . . . . . .beep . . . . . . . .beep . . . . . . .beep . . . . . . . .ad infinitum.
73's de Edd
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