As I said the brake is likely to be sprung-loaded so in the event of a power failure it will engage, so you'll need to physically dis-engage it to see if the motor then spins up normally...
PCB Boards -- Simple Machinery
- Thread starter JohnerH
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Looking at the circuit, I’m guessing that the MOSFET is a Buck converter to create low voltage for the IC chip. The resistor does look to be cooked, however, I’m guessing the MOSFET has blown, and when they go they can create large currents that damage other components, diodes are usually the cause of the failure. So, probably one or two diodes, a resistor, and the MOSFET would be my prime suspects.
I’d like to know where the wires go from the PCB. The ‘peg’ board next to the IC looks to allow the counter to be ‘programmed’ for the count before it starts to recount (it counts from 0 to 9), and then restarts, but can be programmed to restart at any number. So, I’m guessing it’s used to turn in the brake for a set time.
I’d like to know where the wires go from the PCB. The ‘peg’ board next to the IC looks to allow the counter to be ‘programmed’ for the count before it starts to recount (it counts from 0 to 9), and then restarts, but can be programmed to restart at any number. So, I’m guessing it’s used to turn in the brake for a set time.
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Is this inside the motor itself? (sounds mechanical, so I would assume so)
This is so far out of my knowledge bank it feels like rocket science...
Could you kindly expand on this? Think of me as 5 year old
I’m wondering if this is a simple plugging braking circuit. Ie, two phases of the motor are reversed to make it spin backwards for a short period determined by the counter. There would need to be a couple of contractors with the coils driven by the output of the board. But, that would explain the ‘programming’ of the counter.
Can you trace where the wires from the PCB go to?
Looking at the Video and seeing a L2 label on the PCB board, what I think the PCB is doing is, when the motor is turned off, reversing the direction of rotation of the motor for a short period to stop it. This system of braking is called ‘plugging’. If the circuit isn’t working correctly you could see the motor flicking backwards and forwards which is what it appears to be doing. I suspect if you change the jumper position you can alter the period of if jumping.
Looking at the Video and seeing a L2 label on the PCB board, what I think the PCB is doing is, when the motor is turned off, reversing the direction of rotation of the motor for a short period to stop it. This system of braking is called ‘plugging’. If the circuit isn’t working correctly you could see the motor flicking backwards and forwards which is what it appears to be doing. I suspect if you change the jumper position you can alter the period of if jumping.
This is the programming board, the numbers refer to the count of the chip, ie I’m guessing how long it reverses the motor. Just for giggles, move the jumper to another location on the board and see if the twitching frequency if the motor changes, I think it will.
Fault finding on PCBs is fairly straight forward if yoi have a knowledge of electronics. Doing it from a few pictures and when it was around 30 years ago you last earned your living as an electronics engineer who wasn’t very good at it
is a challenge.
So, you first need to make a guess what the circuit is doing, you can see that there is a micro chip, labelled HCF4071BF. You can type this into google to find out what it is. It’s a counter and needs a low DC voltage to,power it up. So, on the PCB must be a low voltage power supply to change the mains voltage into something it can use. I can see a TYN816, which is the thing bolted to the heat sink. This is in simple terms is a 40A switch. I can also see the big light blue component which is 680pF capacitor, and the yellow disk shaped thing on its RHS is an inductor. On the left hand side of the light blue capacitor, are three components laying on the board, two black and one orange. They are all diodes, or, flow control valves that only allow electricity to flow in one direction. The diode in the middle is orange with a black band that indicates to me it’s a zener diode. This will have a number on it like 10 or 15. This is a Voltage reference diode, and starts to conduct when the voltage is above a certain value, the value printed upon it. This is what will be used I think for setting the low voltage value that is powering up the counter. Ie probably 10 or 15volts.
The two blue cylinders above the large light blue capacitor are also capacitors. These capacitors are smaller and are polarised, so will be in the low voltage side of the circuit. They are typical of what is used in a power supply to smooth out the voltage.
All of these components are what is needed to make a buck converter. They can also be used for many other things, but, I can’t see anything else that jumps out to me that it is power supply. The circuit could be used to generate a DC current that is injected into the motor to break it as an alternative. What I can’t see is enough diodes to make a full bridge rectifier, which is needed for both circuits. A bridge rectifier, takes the negative half of the ac and flips it around to make it positive. It could just use a half bridge, which requires just two diodes, which I do see.
The counter is a timer, the jumper board allows the timer to be programmed. We know this PCB does something to the motor, so it must be involved with breaking. I only know of three methods of breaking a motor, injecting a DC current into it, mechanical breaking and plugging where the motor is reversed for a short period. I’m discounting mechanical breaking as you say the motor runs if you wire it up directly, so that leaves two methods of breaking. I don’t see enough components to make a DC break, so my guess is that it’s switching the direction of the motor.
Looking at the video it would suggest that the plugging action is working all of the time. If you move the jumper, and the frequency of the twitching changes we then know that the power supply and the counter are all alive and working. The fault is with the triggering of the breaking action. This means that the ‘switch’ or MOSFET is healthy and we can rule out a lot of the circuit when trying to work out what’s wrong.
To confirm my thoughts the six wires from the PCB need to be traced to see what they connect to. That will give us a better clue what’s going on.
As I’ve said, I was nit a very good electronics engineer over 30 years ago, I could be completely wrong and would welcome the comments of a more experienced and far wiser electronics engineer.
is a challenge. So, you first need to make a guess what the circuit is doing, you can see that there is a micro chip, labelled HCF4071BF. You can type this into google to find out what it is. It’s a counter and needs a low DC voltage to,power it up. So, on the PCB must be a low voltage power supply to change the mains voltage into something it can use. I can see a TYN816, which is the thing bolted to the heat sink. This is in simple terms is a 40A switch. I can also see the big light blue component which is 680pF capacitor, and the yellow disk shaped thing on its RHS is an inductor. On the left hand side of the light blue capacitor, are three components laying on the board, two black and one orange. They are all diodes, or, flow control valves that only allow electricity to flow in one direction. The diode in the middle is orange with a black band that indicates to me it’s a zener diode. This will have a number on it like 10 or 15. This is a Voltage reference diode, and starts to conduct when the voltage is above a certain value, the value printed upon it. This is what will be used I think for setting the low voltage value that is powering up the counter. Ie probably 10 or 15volts.
The two blue cylinders above the large light blue capacitor are also capacitors. These capacitors are smaller and are polarised, so will be in the low voltage side of the circuit. They are typical of what is used in a power supply to smooth out the voltage.
All of these components are what is needed to make a buck converter. They can also be used for many other things, but, I can’t see anything else that jumps out to me that it is power supply. The circuit could be used to generate a DC current that is injected into the motor to break it as an alternative. What I can’t see is enough diodes to make a full bridge rectifier, which is needed for both circuits. A bridge rectifier, takes the negative half of the ac and flips it around to make it positive. It could just use a half bridge, which requires just two diodes, which I do see.
The counter is a timer, the jumper board allows the timer to be programmed. We know this PCB does something to the motor, so it must be involved with breaking. I only know of three methods of breaking a motor, injecting a DC current into it, mechanical breaking and plugging where the motor is reversed for a short period. I’m discounting mechanical breaking as you say the motor runs if you wire it up directly, so that leaves two methods of breaking. I don’t see enough components to make a DC break, so my guess is that it’s switching the direction of the motor.
Looking at the video it would suggest that the plugging action is working all of the time. If you move the jumper, and the frequency of the twitching changes we then know that the power supply and the counter are all alive and working. The fault is with the triggering of the breaking action. This means that the ‘switch’ or MOSFET is healthy and we can rule out a lot of the circuit when trying to work out what’s wrong.
To confirm my thoughts the six wires from the PCB need to be traced to see what they connect to. That will give us a better clue what’s going on.
As I’ve said, I was nit a very good electronics engineer over 30 years ago, I could be completely wrong and would welcome the comments of a more experienced and far wiser electronics engineer.
WARNING - capacitors in this type of circuit can hold onto the electricity when the power is switched off for a long time and can cause an electrical shock that can be fatal. In a good design there will be a bleed resistor to stop this happening…..but that’s in a good design!
Onky stick your fingers around this board if you KNOW what you’re doing.
Onky stick your fingers around this board if you KNOW what you’re doing.
What age is this machine ? There is a thread on the UKW but from 2002 and does your machine look like this with that big enclosure on the front ?
It looks like this machine is an ancestor of the later PT107 and over the years cost savings have taken there toll so now no PCB. To save any hassle you could remove this PCB and wire the machine up without, this is the wiring for the 107 but make sure your limit switches can handle the motor current otherwise make sure they are in the control side of the wiring like in the diagram in post 12.
It looks like this machine is an ancestor of the later PT107 and over the years cost savings have taken there toll so now no PCB. To save any hassle you could remove this PCB and wire the machine up without, this is the wiring for the 107 but make sure your limit switches can handle the motor current otherwise make sure they are in the control side of the wiring like in the diagram in post 12.
The latest photos certainly help.
The big chip, centre bottom appears to be a quad, 2 input nand gate. CMOS logic.
That probably means nothing to you. That's ok. It's a chip that can be used with some resistors and a capacitor to make a simple inverting, latching or pulse circuit. It needs DC power below about 20v. Moving the jumper link probably does select a different resistor which will change the time.
Some components on the board will be making the DC and the device with the alloy heatsink will be boosting the current handling of the circuit to operate a solenoid or some such related to the brake.
I'm going to volunteer the luddite approach as a cheap backup.
1. You just told us that the motor spins perfectly well when you connect it direct to mains. Nothing else really matters. If it spins, then any mechanical brake on the motor is feeble enough that the motor spins anyway.
2. You could open up the motor to take a look. That isn't usually too difficult. If you find a brake, just take out the moving parts to disable it. You have a PT in a home shop. You don't need to comply with HSE regs that the machine must stop in under 10 sec. You're not on the clock, won't be hustling and can wait while it stops.
3. Spend £30 odd on a new DOL starter to start and stop the machine, chuck the original control box with the cheap kedu NVR switch away and wire the safety switch into the start/stop circuit of the starter to keep that protection.
Cheap fix, less to go wrong in future.
The big chip, centre bottom appears to be a quad, 2 input nand gate. CMOS logic.
That probably means nothing to you. That's ok. It's a chip that can be used with some resistors and a capacitor to make a simple inverting, latching or pulse circuit. It needs DC power below about 20v. Moving the jumper link probably does select a different resistor which will change the time.
Some components on the board will be making the DC and the device with the alloy heatsink will be boosting the current handling of the circuit to operate a solenoid or some such related to the brake.
I'm going to volunteer the luddite approach as a cheap backup.
1. You just told us that the motor spins perfectly well when you connect it direct to mains. Nothing else really matters. If it spins, then any mechanical brake on the motor is feeble enough that the motor spins anyway.
2. You could open up the motor to take a look. That isn't usually too difficult. If you find a brake, just take out the moving parts to disable it. You have a PT in a home shop. You don't need to comply with HSE regs that the machine must stop in under 10 sec. You're not on the clock, won't be hustling and can wait while it stops.
3. Spend £30 odd on a new DOL starter to start and stop the machine, chuck the original control box with the cheap kedu NVR switch away and wire the safety switch into the start/stop circuit of the starter to keep that protection.
Cheap fix, less to go wrong in future.
And just glance at this old thread...
From a couple of years back, someone has effectively the same machine under a different brand.
No PCB in that one by the look of it. But the box on the front and the kedu switches look to be the same as yours - a rotary and a JD2 solenoid switch operating 4 single pole contacts.
https://www.ukworkshop.co.uk/thread...er-thicknesser-wiring-dia.44564/#post-1597432
Switch detail from the web
From a couple of years back, someone has effectively the same machine under a different brand.
No PCB in that one by the look of it. But the box on the front and the kedu switches look to be the same as yours - a rotary and a JD2 solenoid switch operating 4 single pole contacts.
https://www.ukworkshop.co.uk/thread...er-thicknesser-wiring-dia.44564/#post-1597432
Switch detail from the web
The TO220 cased device is a TYN816 which is a 16A, 800V SCR. The CMOS device is an HCF4017BE decade counter.
The LV for the CMOS can be generated in a number of ways and without drawing out the schematic it's impossible to say - it could be a simple capacitor dropper or using one of the TO92 cased HV/LV regulators, e.g. an LR8 - there is no LV SMPS on this board. The yellow disc thing is a TVS (definitely - not an inductor or anything else) - basically something that suppresses spikes on the mains input to the PCB - they are cheap and common and often fail (they are a sacrificial component), however if it fails that generally means no more spike-on-mains protection rather than motor-exhibiting-delirium-tremens, i.e. not important at this stage.
The SCR is almost certainly used for turning the motor on or off. I have a suspicion the 4017 is being used as part of an UV/OV lockout, especially because of the 3x4 pin header with jumper next to it and the markings: "1-min 8-max" with 8 positions for the jumper.
Some resistors on the PCB are definitely cooked, e.g. bottom left. Something caused that, so just replacing the resistors is probably not that helpful - need to find the root cause of the failure first.
Knowing the part numbers on the TO92 (small black three-legged) devices would help as then the schematic can be drawn.
Finding an original manual for this unit (RSPT260) would definitely help too...
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@deema , Would this hold true if there's components on the PCB that are blown?
And also, if this is the only function of the PCB, why does one need it? I know breaking is needed, but again, this machine isn't getting sold.
I'll try this if I get a chance this week. Any position?
I'll try and get some answers on that this week also.Fault finding on PCBs is fairly straight forward if yoi have a knowledge of electronics. Doing it from a few pictures and when it was around 30 years ago you last earned your living as an electronics engineer who wasn’t very good at it
So, you first need to make a guess what the circuit is doing, you can see that there is a micro chip, labelled HCF4071BF. You can type this into google to find out what it is. It’s a counter and needs a low DC voltage to,power it up. So, on the PCB must be a low voltage power supply to change the mains voltage into something it can use. I can see a TYN816, which is the thing bolted to the heat sink. This is in simple terms is a 40A switch. I can also see the big light blue component which is 680pF capacitor, and the yellow disk shaped thing on its RHS is an inductor. On the left hand side of the light blue capacitor, are three components laying on the board, two black and one orange. They are all diodes, or, flow control valves that only allow electricity to flow in one direction. The diode in the middle is orange with a black band that indicates to me it’s a zener diode. This will have a number on it like 10 or 15. This is a Voltage reference diode, and starts to conduct when the voltage is above a certain value, the value printed upon it. This is what will be used I think for setting the low voltage value that is powering up the counter. Ie probably 10 or 15volts.
The two blue cylinders above the large light blue capacitor are also capacitors. These capacitors are smaller and are polarised, so will be in the low voltage side of the circuit. They are typical of what is used in a power supply to smooth out the voltage.
All of these components are what is needed to make a buck converter. They can also be used for many other things, but, I can’t see anything else that jumps out to me that it is power supply. The circuit could be used to generate a DC current that is injected into the motor to break it as an alternative. What I can’t see is enough diodes to make a full bridge rectifier, which is needed for both circuits. A bridge rectifier, takes the negative half of the ac and flips it around to make it positive. It could just use a half bridge, which requires just two diodes, which I do see.
The counter is a timer, the jumper board allows the timer to be programmed. We know this PCB does something to the motor, so it must be involved with breaking. I only know of three methods of breaking a motor, injecting a DC current into it, mechanical breaking and plugging where the motor is reversed for a short period. I’m discounting mechanical breaking as you say the motor runs if you wire it up directly, so that leaves two methods of breaking. I don’t see enough components to make a DC break, so my guess is that it’s switching the direction of the motor.
Looking at the video it would suggest that the plugging action is working all of the time. If you move the jumper, and the frequency of the twitching changes we then know that the power supply and the counter are all alive and working. The fault is with the triggering of the breaking action. This means that the ‘switch’ or MOSFET is healthy and we can rule out a lot of the circuit when trying to work out what’s wrong.
To confirm my thoughts the six wires from the PCB need to be traced to see what they connect to. That will give us a better clue what’s going on.
Well, after reading what you've put down seem your experience is still very relevant
@Spectric ,Yep, that's my boy.
That's what I'm thinking, this looks pretty simple. I can't where the capacitor lives?
Thanking you Sir, I'll dive into this thread.
I have the original manual, no indication of the ciruit or PCB information.
If I hard wire this thing with a PCB, what can realistically go wrong?
@JohnerH thank you, but I made the school boy error of assuming what a component was and @nickds1is clearly a far more competent electronics engineer and properly looked up what the power device is. It’s a SCR which stands for a Silicone Controlled Rectifier. It’s basically a diode that you can switch on to conduct. I’ve seen them used to control DC motors, where only one needs to be used, but never for a AC motor, they only conduct on half of the wave form cycle, which is why they are sometimes called half rectifiers. It would be really really interesting to see the schematic of this circuit to find out what it does, as Nick has suggested if you can see what the markings are in the black three legged devices between us all we can work out what it’s actually doing.
If you hard wire the motor through a suitable DOL (motor starter) and if the PCB is some form of brake, you will just loose the braking function. So the machine will not be regulations compliant, and you can’t use it with employees. Typically for this size of machine before the PUWR regs came in, none had any form of braking. The regs are to prevent people getting injured because they became impatient waiting for the machine to slow down and stop and stuck their fingers in / too close.
If you hard wire the motor through a suitable DOL (motor starter) and if the PCB is some form of brake, you will just loose the braking function. So the machine will not be regulations compliant, and you can’t use it with employees. Typically for this size of machine before the PUWR regs came in, none had any form of braking. The regs are to prevent people getting injured because they became impatient waiting for the machine to slow down and stop and stuck their fingers in / too close.
It's unlikely that the board itself will spontaneously experience RUD, so there will have had to have been (an) external event(s).
It's perfectly possible that the resistors are fried because they were initially a bit underrated and long running may have shortened their life. Alternatively, an unexpectedly high main voltage (we get up to 250VAC here out in the country) or a big spike/surge (think: lightning etc.) or network provider issues could have taken the unit out of its safe operating area (SOA). The TVS on the input (the round beigey-orange thing) will only absorb a certain amount of energy - at a certain point they just stop working or in extreme circumstances, they explode leaving black soot everywhere. See the photos below of a blue one (Aqualisa shower mixer controller) and the remains of a beige one (cooker hood fan & light controller)...
Record Power don't have the manual available and I can't find it elsewhere - any chance you can scan & post it (it'll be useful for others too, no doubt). It may give some insight to the use of the 1-8 jumpers, which in turn may explain a lot about how that PCB is supposed to work. It's possible, for instance, that the board implements a "slow-start" rather than over/under voltage protection - pure speculation until there's a schematic.
Whatever happens, that PCB only contains cheap and still-available discrete components - no microcontroller or sealed-up magic - so it most certainly repairable.
My original point remains - just repairing the board without understanding its operating conditions is probably a waste of time - definitely need the whole machine checked.
