If the actuators try to move at the right time then probably the processor is OK. But either the drivers or the power supply may not be OK. And still we have no report on the power supply. Probably the only repairable part of the system.

 

If the actuators try to move at the right time then probably the processor is OK. But either the drivers or the power supply may not be OK. And still we have no report on the power supply. Probably the only repairable part of the system.

Is he trying to fix it or just understand the control mechanism to hack it for something else? From his first post, I don't think there is anything wrong with the machine.

trying to understand its operation.
Would like to reverse engineer this circuit to learn how to control its linear actuators.

 

Good luck on the reverse engineering. In that era I think there was a fair amount of effort spent making it difficult for the competition to copy things. You might have some success getting information from the maker company now that the product is not so current. And there are some repair wizards that might be willing to share some insights as to how they work. But probably you will not find them here.

 

That is a THIN ceramic coating andit should not be abraded because it is protecting the thin-film resistors printed on the substrate underneath. Or iit might be thick-film resistors, I don't recall at this moment.
And while the whole thing seems strong, they are quite brittle and they will break with too much force, not sturdy like IC devices.

This is what I have been able to recover from the board. There are two control circuits here "bight" and "feed", according to the Patent (provided in the beginning of the thread) description their operation is identical, so I am only concerned with "feed" at the moment. My goal is to determine the location where I could measure the analog signal with my scope for linear actuator before it is amplified. Also, trying to understand where is the signal amplification takes place. I understand the quad is the preamplifier. What is the purpose of the diodes on the right? I suspect they are responsible for the direction of the motion of the linear actuator. I see that position feed back (yellow arrow) goes to the out put (A) of the op amp how does this ensure position regulation. Any help is appreciated. Also what are these components diodes or caps (another image below)? What about the yellow is this a Cap?

 

This is what I have been able to recover from the board. There are two control circuits here "bight" and "feed", according to the Patent (provided in the beginning of the thread) description their operation is identical, so I am only concerned with "feed" at the moment. My goal is to determine the location where I could measure the analog signal with my scope for linear actuator before it is amplified. Also, trying to understand where is the signal amplification takes place. I understand the quad is the preamplifier. What is the purpose of the diodes on the right? I suspect they are responsible for the direction of the motion of the linear actuator. I see that position feed back (yellow arrow) goes to the out put (A) of the op amp how does this ensure position regulation. Any help is appreciated. Also what are these components diodes or caps (another image below)? What about the yellow is this a Cap?
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fixed the error on the in the quad for bight circuit (A)

 

The thing will become understandable and capable of analysis when you are able to draw it as an actual circuit withopamps and transistor stages instead of having it shown as a wiring diagram with no obvious direction. Similar to written text,where the sequence of the words has meaning, the sequence of the functions conveys a lot of information.

 

The thing will become understandable and capable of analysis when you are able to draw it as an actual circuit withopamps and transistor stages instead of having it shown as a wiring diagram with no obvious direction. Similar to written text,where the sequence of the words has meaning, the sequence of the functions conveys a lot of information.

This was my next step. Thank you.

 

Caps, yes.

Those are both capacitors, different flavors because of different value ranges.

 

This was my next step. Thank you.

This is my current attempt at unwrapping the circuit some connections do not make sense to me, there are probably mistakes with the second resistor chip as it was double sided and harder to figure out. I only kept the circuits that relate to the linear actuator system. What I can see on my own is that the main_green is the most likely, the signal buss since all the caps are connected to it. main_beige is a mystery, there is an oscillation frequency that depends on the speed of the machine perhaps it is mixed with the signal. man-brown is probably grounded but not certain. I see a pair of transistors working in tandem but what their purpose is beyond my comprehension. D1 D2 D3 D4 must be doing some rectification. If someone sees more then I would appreciate you input.

 

This is my current attempt at unwrapping the circuit some connections do not make sense to me, there are probably mistakes with the second resistor chip as it was double sided and harder to figure out. I only kept the circuits that relate to the linear actuator system. What I can see on my own is that the main_green is the most likely, the signal buss since all the caps are connected to it. main_beige is a mystery, there is an oscillation frequency that depends on the speed of the machine perhaps it is mixed with the signal. man-brown is probably grounded but not certain. I see a pair of transistors working in tandem but what their purpose is beyond my comprehension. D1 D2 D3 D4 must be doing some rectification. If someone sees more then I would appreciate you input.
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I have revised the servo circuit my op-amps drawing was up side down, I think it is much closer to being correct now. I would appreciate if someone could help me Identify how this operates. I have studied some of the servo control circuits and I see some resemblance but there is a lot more going on here. Does anyone see anything familiar?

 

I have revised the servo circuit my op-amps drawing was up side down, I think it is much closer to being correct now. I would appreciate if someone could help me Identify how this operates. I have studied some of the servo control circuits and I see some resemblance but there is a lot more going on here. Does anyone see anything familiar?
View attachment 241574

 

OK, But as I look at the feedback path it is open after the first amplifier stage(OP7B). So there is a connection missing there.
usually the feedback and command voltages are buffered and scaled and then subtracted to produce an error signal that drives whatever is producing the feedback signal.

 

Strange resistor values.

Those are measured values. Notice how they are all within 5% of the E12 resistor series? Funny how that works, right? Ha.

 

OK, But as I look at the feedback path it is open after the first amplifier stage(OP7B). So there is a connection missing there.
usually the feedback and command voltages are buffered and scaled and then subtracted to produce an error signal that drives whatever is producing the feedback signal.

This is all there is for the B op-amp, unless the chip orientation is somehow still incorrect.

 

It is a double sided PCB and it is probable that a conductor runs beneath the IC, or into a via on the other side. It may take some meter probing to find out.

 

It is a double sided PCB and it is probable that a conductor runs beneath the IC, or into a via on the other side. It may take some meter probing to find out.

I revised the circuit yet again I believe I misinterpreted power transistors for power diodes in the TO−220 type package, circuit looks more logical now all though I still don't quiet understand its exact operation but I can at least identify the stages. Let me know if you agree or not with my assumptions please. Also could someone ID these power transistors.

 

The conclusin about the amplifier seems to be reasonable and correct. The conclusion about the "feedback circuit" is also correct. Servo systems use phase shifts to deliver what is called "lead-lag compensation", to better reduce the error and add stability. That part can be complicated. C4 and C5 seem to be part of that feedback portion.

 

Are those Darlington transistors?

Probably not darlingtons because darlington transistor gain is high enough that two stages would not be required.

 

Like I said, in addition, the circuit, with 2stages in cascade,would not use darlingtons.