- Thread starter tony69
- Start date
According to thie earlier thread:
Hydrovane 502 contactor not locking
I have a Hydrovane 502 Single Phase 2.2Kw Motor that was working fine until a fuse on the supply blew (due to being too small). The supply has been upgraded now but now the contactor won't lock on (otherwise the compressor seems to run fine while the start button is pressed) From the manual...
www.mig-welding.co.uk
Compared to the expected value, that resistance value sounds about right.
That leaves the tiny 1-Amp BC377 as the output switching device, responsible for enabling or dropping-out the contactor in the event of overtemperature. It seems a bit wimpy for that job...?
From where it is wired, just after the bridge rectifier, I would guess that the component with the heatsink is a voltage regulator.
That leaves the tiny 1-Amp BC377 as the output switching device, responsible for enabling or dropping-out the contactor in the event of overtemperature. It seems a bit wimpy for that job...?
The Emitter of the BC377 is grounded. As an NPN transistor, a positive voltage on the Base will make it conduct and the Collector will be drawn down towards ground. I guess the Collector is wired to A2 on the contactor, and the transistor is supposed to provide a ground as long as there in no overtemp fault.
The Base connects via a diode to Pin 1 of the NE4558, the output of the first Op-Amp. What is the voltage on the Base of the BC377 with respect to ground?
The Base connects via a diode to Pin 1 of the NE4558, the output of the first Op-Amp. What is the voltage on the Base of the BC377 with respect to ground?
Looks like a voltage regulator to me as well; input on pin 1, ground on pin 2 and output on pin 3. Possibly something like a 7824 or similar? I also think that BC377 is switching the contactor and it does seem a bit weedy!
Should hopefully have the circuit sketched out later tonight or tomorrow
OK mate thats great. I may look at swapping out the bc377 for something stronger.
Any suggestions on what I can swap it out for, hopefully a straight forward one lol
Cheers
I wouldn't worry about that at the moment, it was just a comment and I can't see it being your problem. I'm thinking this is more likely to be a suspect connection or temperature sensor fault rather than a component failure as you got it to work briefly back on Post #16. I'm struggling trying to fully trace out the circuit from the photo's as there's a bit of glare on the tracks around the NE4558 that's preventing me seeing things properly, but I think I've got enough info to make a few comments. Going back to this:
PS: In Post #35 I got my start and stop buttons mixed up, 1 and 2 is the stop button which is normally closed. Pressing it once it's running will drop out the 24v supply to the contactor, which will then de-latch.
It might be worth repeating these if you used 23 for your negative multimeter lead, try using either the point where the red temperature sensor wire is terminated or pin 4 on the NE4558 as your negative point and set your meter to DC volts. The readings you got seem fine though , pin 7 rising to 24v when you press the start button suggests the power supply on the board is all fine and that 24v from the start button is going straight into an input on the NE4558. The output of that should switch the BC377, which in turn will ground A2 and energise the contactor. As that's not happening, I'm wondering if it's a temperature sensor problem, although it seems to measure ok. I reckon it could be a thermistor and from what I can see of the circuit, it's resistance will increase with temperature. So a quick test to discount that would be to remove the red & blue wires from the connector on the board and insert a wire link across the terminals. That will simulate a really low temperature, so try that and see if it runs?
PS: In Post #35 I got my start and stop buttons mixed up, 1 and 2 is the stop button which is normally closed. Pressing it once it's running will drop out the 24v supply to the contactor, which will then de-latch.
Any chance of another photo of this as well with that looping red wire from terminal 11 out of the way. I was trying to read the resistor band colours earlier and that wire is obscuring every single one!
Here we go, I think this is the circuit and I've added the resistor values as well. I've assumed the component with the heatsink (which you've now removed in the above photo) is a 24v regulator, such as a 7824. It might be another type / model number but it won't affect the function of the circuit if I've got this wrong.
So the NE4558 is an operational amplifier (op amp) and the output at pin 1 will either be on (24v) or off (0v), depending on the relative voltage levels of the two inputs, pins 2 and 3. If pin 3 voltage is higher than pin 2 the output will be on, if pin 3 voltage is lower than pin 2 then the output will be off. If the output is on, this will trigger the BC377, which in turn will energise the contactor coil at A1 / A2.
95 and 96 is the thermal overload trip (excessive current) and this is a normally closed pair of contacts. 43 and 44 are are pair of normally open contacts. All voltages mentioned below are relative to the 0v rail (temperature sensor red wire or the green / yellow earth wire).
With power applied and no buttons pressed, there will be 24v at terminal 5 on the board (96 on contactor). The combination of resistors R1, R2, R3 and R6 will result in a voltage of around 11.8v at terminal 7 (43 at contactor) as you've already determined. Pressing the start button puts the full 24v onto board terminal 7 (43 on contactor). You also got that earlier so it looks like that part of the circuit is ok.
With no buttons pressed, the voltage at NE4558 pin 3 will be around 4.8v. If we assume the temperature sensor is 124 ohms at ambient as per the other thread mentioned, then the voltage at pin 2 will be around 6.9v. Pin 3 is less than pin 2 so nothing happens. Pressing the start button results in the voltage at pin 3 increasing to around 9.8v, this is now greater than the 6.9v at pin 2, so the NE4558 output is turned on; this energises the contactor and pulls in the various contacts. 43 and 44 are now closed and this maintains the 9.8v at pin 3 even after the start button is released. At this point the circuit is latched in the on state and only three things will unlatch it:
1. Pressing the stop button, which removes the 24v supply.
2. A thermal overload situation, which will cause 95 and 96 to go open circuit and therefore drop the voltage at pin 3 back to 4.8v (NE4558 output will then go off)
3. An increase in temperature at the temperature sensor. As temperature increases, the voltage at pin 2 will increase and once this gets above the 9.8v at pin 3, the NE4558 output will turn off. This is effectively a high temperature trip.
A few things you could measure, all these are relative to the 0v rail, so just connect your negative multimeter lead to the green / yellow wire, set it on DC volts and check the following:
1. Voltage at pin 2
2. Voltage at pin 3 without the start button pressed
3. Voltage at pin 1 without the start button pressed
4. Voltage at pin 3 with the start button pressed
5. Voltage at pin 1 with the start button pressed
Check those points and post up what you find, I should be able to tell from that what has failed.
95 and 96 is the thermal overload trip (excessive current) and this is a normally closed pair of contacts. 43 and 44 are are pair of normally open contacts. All voltages mentioned below are relative to the 0v rail (temperature sensor red wire or the green / yellow earth wire).
With power applied and no buttons pressed, there will be 24v at terminal 5 on the board (96 on contactor). The combination of resistors R1, R2, R3 and R6 will result in a voltage of around 11.8v at terminal 7 (43 at contactor) as you've already determined. Pressing the start button puts the full 24v onto board terminal 7 (43 on contactor). You also got that earlier so it looks like that part of the circuit is ok.
With no buttons pressed, the voltage at NE4558 pin 3 will be around 4.8v. If we assume the temperature sensor is 124 ohms at ambient as per the other thread mentioned, then the voltage at pin 2 will be around 6.9v. Pin 3 is less than pin 2 so nothing happens. Pressing the start button results in the voltage at pin 3 increasing to around 9.8v, this is now greater than the 6.9v at pin 2, so the NE4558 output is turned on; this energises the contactor and pulls in the various contacts. 43 and 44 are now closed and this maintains the 9.8v at pin 3 even after the start button is released. At this point the circuit is latched in the on state and only three things will unlatch it:
1. Pressing the stop button, which removes the 24v supply.
2. A thermal overload situation, which will cause 95 and 96 to go open circuit and therefore drop the voltage at pin 3 back to 4.8v (NE4558 output will then go off)
3. An increase in temperature at the temperature sensor. As temperature increases, the voltage at pin 2 will increase and once this gets above the 9.8v at pin 3, the NE4558 output will turn off. This is effectively a high temperature trip.
A few things you could measure, all these are relative to the 0v rail, so just connect your negative multimeter lead to the green / yellow wire, set it on DC volts and check the following:
1. Voltage at pin 2
2. Voltage at pin 3 without the start button pressed
3. Voltage at pin 1 without the start button pressed
4. Voltage at pin 3 with the start button pressed
5. Voltage at pin 1 with the start button pressed
Check those points and post up what you find, I should be able to tell from that what has failed.
Hi Neil these are the 3 which are being replaced. The one under the heat sink was Purley a accident and got knocked of while moving the compressor with bits hanging out. Silly I know. The other 2 was due to fault (in our head anyway). Being unsure which 1 was at fault we chose to swap both as there so cheap.
Time put to one side for fitting on sunday.
Fingers crossed
Time put to one side for fitting on sunday.
Fingers crossed
