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Schaublin 135 - Help upgrading electrical system

Before I do these checks the thermal cut out red wires are still disconnected, is this OK or should they be reconnected for these tests?
 
I have re-connected the thermal cut off wires to 51/52 and removed the jumper wire.

Removing one of the brake wires from 16/17 results in no change to the current or voltage showing on the PS - it was actually showing 0.45A and 19.8VDC and remained there.

Question when I wired the metal oxide varistors is there a polarity to get right? I did just remove the new ones and replaced with the original just to re-test but still no brake function.
 
When you say that it delivers 17VDC, is it also putting out 6A at that voltage? So it's not possible to increase the voltage beyond 17V?

If the power supply is delivering 6A, the question is, where is that current going? Suppose you disconnect the brake (either at terminal 16 or 17). Does the voltage go up to 32V and the current drops to a much smaller value?


The right way to proceed is to figure out where the 6A of current is going. Do this by disconnecting the safety lock solenoid at terminal 18 or 19, and/or disconnecting the brake at terminal 16 or 17.

Note: the rectifier is entirely disconnected during this entire process, right? You should be feeding DC current into the two 6A fuses via the wires that would normally go to the rectifier + and -.



(1) When the lathe is powered down, and you connect the external power supply, it should provide current to close the safety solenoid and nothing else. If that is NOT the case, then don't proceed further. Give me feedback so we can figure out what is wrong.
It does that
(2) If that IS the case, then you then power up the lathe but leaving the control lever in the middle (zero = off) position, that should close contactor d2, engaging the brake, and close contactor d3, disengaging the safety solenoid.
Solenoid is disengaged but the brake is not on
You can test the brake as you did before. Disconnect wires 16 and 17 that lead to the brake and connect to your PS. Test brake as you did earlier.
Just tried this and the brake works fine, kicks in around 9-10VDC which is roughly where it should as I understand.
Assuming that you connected the two grey feed wires to the AC contacts and not the +/- contacts, yes, that's OK. Personally I would have left them disconnected (and insulated to avoid contact with anything) until we were ready to test the rectifier.
Yes indeed
We won't connect the rectifier until we have verified that everything downstream is working right.
 
Before I do these checks the thermal cut out red wires are still disconnected, is this OK or should they be reconnected for these tests?
Should not matter, since motor is not running to overheat. But so that it is not forgotten later, remove the jumper and reconnect.
 
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I have re-connected the thermal cut off wires to 51/52 and removed the jumper wire.

Removing one of the brake wires from 16/17 results in no change to the current or voltage showing on the PS - it was actually showing 0.45A and 19.8VDC and remained there.
Then you should be able to set it to 32V. Either the current limit is set too low or the voltage limit is set too low.

Question when I wired the metal oxide varistors is there a polarity to get right? I did just remove the new ones and replaced with the original just to re-test but still no brake function.
No, there is no polarity to the MOVs
 
OK, the brake is working but does NOT turn on when the lathe is powered up and the control lever is in the off position.

(1) Make sure that your power supply is set to 32V. It is going through a dropping resistor, so this will put a lower voltage on the brake.

(2) Make sure that your power supply current limit is set high enough to provide the current needed to (a) turn on the brake + (b) turn on the solenoid

(3) If the lathe is powered and the control lever is in position 0 and d2 is closed, and the brake is NOT engaged, then disconnect
the brake from terminals 16 and 17, and check the voltage on those two terminals. You should see the DC voltage there, which should be turning on the brake.

(4) If not, trace that circuit back through contactor d2. Study my schematic in post 224. There should be DC voltage across d2 R/S and across d2 9/T. That is the input. Then there should be DC voltage across d2 U/V and d2 10/W. This is the output. Look at the schematic in post 224, to see how it is connected when d2 is closed.

One thing that might be going wrong, which can explain what you are seeing, is that the d2 normally closed (NC) contacts 13/14 and 11/12 are NOT opening when d2 is closing. When d2 is closed you should see the DC voltage across d2 13/14 and also across d2 11/12. Do you?

If not, then turn off the lathe. Disconnect the wires from d2 11/12/13/14 , disconnect the A/B terminals driving d2. Then open and close the contactor by connecting d2 A/B to your mains. Check that the contact pair 13/14 shows zero resistance (closed circuit) when d2 is OFF and that 13/14 shows high resistance (open circuit) when d2 is ON. Same for the 11/12 contact pair.

If the d2 11/12 contact pair or the d2 13/14 contact pair is welded in the closed position, this could explain what you are seeing. This would "short out" the DC power supply when the brake is turned on. It is why we are testing with your PS and not with the transformer/rectifier!

Another way to test this hypothesis: starting with everything reconnected (but still using the external power supply) disconnect the wire from d2/12 to terminal block 17 and from d2/14 to terminal block 16. This removes the d2 NC contacts from the circuit. Now power up the lathe. Does the brake now work correctly? If so, the problem is one or both of the d2 NC contacts: they are not opening when the contactor turns on.
 
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OK, the brake is working but does NOT turn on when the lathe is powered up and the control lever is in the off position.

(1) Make sure that your power supply is set to 32V. It is going through a dropping resistor, so this will put a lower voltage on the brake.

(2) Make sure that your power supply current limit is set high enough to provide the current needed to (a) turn on the brake + (b) turn on the solenoid
I'm not getting close to 32VDC from the PS at any stage even with knobs turned right round and amps set to 6A
(3) If the lathe is powered and the control lever is in position 0 and d2 is closed, and the brake is NOT engaged, then disconnect
the brake from terminals 16 and 17, and check the voltage on those two terminals. You should see the DC voltage there, which should be turning on the brake.
Yes I do around 11VDC
(4) If not, trace that circuit back through contactor d2. Study my schematic in post 224. There should be DC voltage across d2 R/S and across d2 9/T. That is the input. Then there should be DC voltage across d2 U/V and d2 10/W. This is the output. Look at the schematic in post 224, to see how it is connected when d2 is closed.

One thing that might be going wrong, which can explain what you are seeing, is that the d2 normally closed (NC) contacts 13/14 and 11/12 are NOT opening when d2 is closing. When d2 is closed you should see the DC voltage across d2 13/14 and also across d2 11/12. Do you?
Yes 11VDC
If not, then turn off the lathe. Disconnect the wires from d2 11/12/13/14 , disconnect the A/B terminals driving d2. Then open and close the contactor by connecting d2 A/B to your mains. Check that the contact pair 13/14 shows zero resistance (closed circuit) when d2 is OFF and that 13/14 shows high resistance (open circuit) when d2 is ON. Same for the 11/12 contact pair.

If the d2 11/12 contact pair or the d2 13/14 contact pair is welded in the closed position, this could explain what you are seeing. This would "short out" the DC power supply when the brake is turned on. It is why we are testing with your PS and not with the transformer/rectifier!

Another way to test this hypothesis: starting with everything reconnected (but still using the external power supply) disconnect the wire from d2/12 to terminal block 17 and from d2/14 to terminal block 16. This removes the d2 NC contacts from the circuit. Now power up the lathe. Does the brake now work correctly? If so, the problem is one or both of the d2 NC contacts: they are not opening when the contactor turns on.
I do get 11VDC at 16 & 17 when the wires are all connected but no brake, the brake tested fine when connected to the PS by itself and was working strongly at 10VDC so it should show something when 11VDC is at the wire ends?

Shall I do the last test by disconnecting d2/12 & 14?
 
Not sure if this has any impact as suspect it does not but the chuck guard is not fitted and I know it has a safety switch as part of this system, I'm guessing this has been over-riden as the lathe would not run I assume if it had not been done?

How can you have 11VDC at the wire ends and the brake does not work yet remove them and power them directly with 10VDC and it works fine?
 
Just a quick update.

Went back up and tested again, removed the PS from the internal wiring and connected directly to the brake, at around 7VDC the brake went on and off as I turned the PS on and off so this was working fine.

The PS output voltage display niggled me as it was showing no more than 17-18VDC, checked directly across it output terminals and it was reading 31VDC! (the display must be faulty or something is adrift).

Reconnected the PS to the internal blue wires and switched on the lathe power, for around 10 on/off cycles all was working well and the brake worked, then all of a sudden it stopped working, I did hear what I thought was the sound of a tripping contactor at that moment too - may just be in my head?!?!

Removed the internal wiring link to the PS and re-connected direct to the brake blue wires, turned the PS to around 8VDC and 0.4A and the brake worked fine. Turned the lathe on after turning off the PS and then tested the brake by turning off the lathe and then switching on the PS to activate the brake - faultless, the brake was working well at around 8VDC (Voltmeter not the PS display)

All very strange?
 
Perhaps the existing capacitor is shorted internally. Replace the capacitor with a new one. Pay attention to the polarity.

If this does not fix the problem, I am starting to suspect that something is wrong with your PS. If you have spare 6A fuses, then let's shift to testing with the built in DC supply. The main risk is burning 6A DC power supply fuses.

Connect the (gray?) wires from the transformer secondary to the bridge rectifier diode AC connections. Then connect the blue wires going to the DC 6A fuses to the bridge rectifier diode + and - connection, respecting the polarity of your red and black heat shrink tubing. Then test again.

If you do not have spare 6A fuses, let me know and we will try plan B. Or, if you want to be conservative, stay with the PS but read the alternatives below.
 
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I'm not getting close to 32VDC from the PS at any stage even with knobs turned right round and amps set to 6A

Yes I do around 11VDC

Yes 11VDC
Do you see 11 volts both at the PS output and at the brake input?? If the voltages are different, then use the voltmeter to test voltages, starting at the PS and moving downstream through the contactor to the brake.

When you are in this condition, what current does the PS show that it is providing? Either the PS is at its 6A limit, or the voltage needs to be turned up at the PS, or the PS is not working correctly. Note that the PS may need to be reset each time that the current limit is tripped! Pay attention to the CV and CC lights!!

I do get 11VDC at 16 & 17 when the wires are all connected but no brake, the brake tested fine when connected to the PS by itself and was working strongly at 10VDC so it should show something when 11VDC is at the wire ends?

Shall I do the last test by disconnecting d2/12 & 14?
Yes. First replace the capacitor, just in case that is shorted. Respect the polarity.
 
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Not sure if this has any impact as suspect it does not but the chuck guard is not fitted and I know it has a safety switch as part of this system, I'm guessing this has been over-riden as the lathe would not run I assume if it had not been done?
I don't know. You'll have to figure out how the safety switch is connected. Trace the wires and add the switch to the schematic. Otherwise I can't tell you what effect it will have.
How can you have 11VDC at the wire ends and the brake does not work yet remove them and power them directly with 10VDC and it works fine?
Is it still 11VDC at the wire ends AFTER you have connected the brake? Or does connecting the brake make the voltage drop? I think that the PS may have switched into a constant current mode and when you connect the brake the voltage drops.
 
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Just a quick update.

Went back up and tested again, removed the PS from the internal wiring and connected directly to the brake, at around 7VDC the brake went on and off as I turned the PS on and off so this was working fine.
How much current is required at that voltage? Also, did you use the voltmeter to check that the PS voltage on the PS display agrees with what is actually on the wires?

The PS output voltage display niggled me as it was showing no more than 17-18VDC, checked directly across it output terminals and it was reading 31VDC! (the display must be faulty or something is adrift).
One possibility is this. If the PS is tripped by an overcurrent condition, perhaps it needs to be reset, for example by power cycling. Until you reset it the display voltage and actual voltage don't agree?

Reconnected the PS to the internal blue wires and switched on the lathe power, for around 10 on/off cycles all was working well and the brake worked, then all of a sudden it stopped working, I did hear what I thought was the sound of a tripping contactor at that moment too - may just be in my head?!?!
Could that tripping device be in the PS? It is providing more than 6A, so turns off the PS internally?

Removed the internal wiring link to the PS and re-connected direct to the brake blue wires, turned the PS to around 8VDC and 0.4A and the brake worked fine. Turned the lathe on after turning off the PS and then tested the brake by turning off the lathe and then switching on the PS to activate the brake - faultless, the brake was working well at around 8VDC (Voltmeter not the PS display)

All very strange?
Study the behaviour of the front panel lights on the PS. One of them shows that the PS can deliver enough current to maintain the voltage. This is probably labeled CV for "constant voltage". Then a second light shows when the PS can not deliver enough current to maintain the voltage. This light is probably called CC for "constant current".

Is your "working correctly" behaviour when the CV light is on. Then the PS reaches its current limit and the CC light turns on, and it reduces the voltage. Maybe that is the tripping noise.

Be a detective and you can figure it out.

PS: I have a theory. The NC contact pair is slow to open. Before it opens it shorts out the power supply and trips the CC cutoff. Disconnecting d2/12 and d2/14 should fix that. Test with PS.
 
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I have a question directed to SomeoneSomewhere...
... the UK soldiers on.
Changing topics, and referring to the schematic in post 224.

Do you understand the idea behind the NC aux contacts d2 11/12 and d2 13/14? When the brake is turned on, if the main contactor contacts close *before* the NC aux contacts open, then the NC aux contacts short out the DC power supply!

Can you explain why they have put a 250uF capacitor in the circuit in that way? Suppose we disconnect d2/12 and d2/14. How does that change the functioning of the circuit? The capacitor must be to source the current surge when the brake is initially connected and perhaps to provide a buffer/current path to handle the back EMF when the brake is disconnected. But I don't get how it works.
 
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Marc, I went back through this thread and gathered the different resistance values that you have measured. For example, you measured that the adjustable power resistor r1 is 26 ohms, that the current drawn by the brake is 1.6 amperes at 24 volts, which means that the brake is 15 ohms, and that the safety solenoid current is 0.5 amps at 30 volts, which means that the solenoid is 60 ohms. I have added those resistance values to the circuit diagram below.

A couple of points of interest. First, with the measured and inferred resistance values for r1 and for the brake, the voltage on the brake will be the DC supply voltage x 15/(26+15) = 0.366 x supply voltage. So for your 32V power supply you should see 11.7 volts on the brake. For the (roughly) 40VDC supply that you will get from the rectifier, it will be slightly higher, around 14 volts. So the 11 volts that you are seeing at the brake contacts makes sense.

Note that if the PS voltage is substantially below 32V, you may not get a high enough voltage to turn on the brake, since only about 1/3 of that voltage is applied to the brake, with the remainder generating heat in the resistor r1.

Second point is current draw. The safety solenoid draws about 0.5A from the PS. The brake should draw about 32V/41 ohms = 0.8A. When one of these is turned on, the other is turned off. So the total current drawn from your DC PS (when set to 32V at the output) should be maximum about 0.8A.

Can you confirm these figures? When the brake is working and the safety solenoid is turned off, you should see about 0.8A of current draw at 32V from the PS, with a brake voltage around 11 or 12V. When the brake is off and the safety solenoid is on you should see about 0.5A of current draw at 32V from the PS.

The strange behaviour that you are seeing, reported above, could be happening because the NC contacts d2 11/12 and d2 13/14 are not opening until AFTER the main contacts in d2 have closed. This temporarily shorts out the power supply through those NC contacts, drawing more than 6A from the power supply, which puts it into constant current (CC) mode. It then reduces the voltage or even shuts down, and the brake does not operate.

The easy way to confirm the behaviour of the d2 NC contacts would be to disconnect d2 12 and d2 14, then see if the strange behaviour that you have reported goes away. As always, take lots of photos and clearly label wires before disconnecting them.

I still don't understand the role of the capacitor k1 in the circuit. I think that it may form a tuned LC circuit with the inductance of the brake, intended to act as a low-pass filter to reduce the current surge when the brake is turned off. Does your manual for the brake list the inductance (it will be in Henries or milliHenries or H or mH) of the coil? If it gives that value then I can calculate the time-constant of the low-pass filter and perhaps understand its purpose better.

Anyway, I think you should try to understand if the current draws that I describe above correspond to what you see when the brake is working, and if the odd behaviour has to do with your power supply either mis-behaving or shutting off because of strange behaviour in the d2 NC contacts. If the current draws that I am describing correspond to what you have observed then I think you can also experiment with reconnecting the bridge diode and get rid of your power supply. However if the d2 NC contacts are misbehaving you may burn out one or both of the 6A fuses. Disconnecting d2 12 and d2 14 will avoid that, however it then means that the capacitor is no longer playing the role it was designed for, which I do not yet understand.

Screenshot 2023-08-19 at 04.52.23.png
 
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I have a question directed to SomeoneSomewhere...

Changing topics, and referring to the schematic in post 224.

Do you understand the idea behind the NC aux contacts d2 11/12 and d2 13/14? When the brake is turned on, if the main contactor contacts close *before* the NC aux contacts open, then the NC aux contacts short out the DC power supply!
I can see that, bit like relying on c1/c2 and c3/c4 to close/open without any overlap (which seems a challenge when you are working with mechanical devices)
Can you explain why they have put a 250uF capacitor in the circuit in that way? Suppose we disconnect d2/12 and d2/14. How does that change the functioning of the circuit? The capacitor must be to source the current surge when the brake is initially connected and perhaps to provide a buffer/current path to handle the back EMF when the brake is disconnected. But I don't get how it works.
Not being an electrician and my knowledge of capacitors only being that they store energy before releasing it, I would assume it is in the system to prevent exactly what you suggest, being able to absorb and give a short window if time to prevent cross over of the contacts opening and closure and potential shorting.
 
Appreciate the long detailed update, I will get to these tests today and report back.

All I have re the brake is at the end of the document attached.

Shall I ask my 'contact' if he can shed light on k1?
 

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  • SERVICE INSTRUCTIONS 135 en anglais.pdf
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Appreciate the long detailed update, I will get to these tests today and report back.
ok, I think we are close to having it working right
All I have re the brake is at the end of the document attached.
Nothing relevant there
Shall I ask my 'contact' if he can shed light on k1?
Sure, can’t do any harm. Perhaps it is a standard circuit for such things.
 
Reply from my guru re k1..

It´s mounted to reduce the contact-fire at the relay contact and the brake comes a little bit faster.

Remember: You have direct current at the brake.
 








 
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