Dc power supply in cnc not working

[stj]

Re: Dc power supply in cnc not working

sounds fucked to me,
the only caps with a discharge resistor are motor caps

[sam_sam_sam]

Re: Dc power supply in cnc not working

sounds fucked to me,
the only caps with a discharge resistor are motor caps

This is not away true ( but generally speaking this is true ) I have seen some high UF value capacitors have a resistor as part of the capacitor that are not motor run capacitor or start capacitor

You will see this in some VFD drive that have this type of capacitor with a resistor in them as well

I have also see motor run and start capacitors with out resistors on them as well it might because whoever manufacturer them decide not to include them for money reason probably

[shelby5041]

Re: Dc power supply in cnc not working

hi samsam

well i installed the replacement capacitor today and found out that the LM338 may not be bad after all

it may be an issue further down the line

i put cap in and tested voltage at cap and it was 44v which is good

i then tested voltage output at the LM338 and it was 43v and i was like WFT?????

last time i checked LM 338 i was getting 1.5V

i then noticed when i checked it today i did not have the 42v output harness connected to the 3 stepper motor driver boards...so i then connected the 42output to all 3 driver baords and then i lost 42v and i was getting 1.5v again

so i then started troubleshooting the 3 driver boards that the 42v output goes to and found out that 1 of the driver boards may be bad

if i connect 2 of the driver boards(lets call A and
B) i get 42v output to the driver boards but if i connect the 3rd one (lets call it C)i then lose 42v and i get 1.5v to the driver baords...

if i disconnect a and b and just connect the 42v output to the C board i still get 1.5v output

however if i keep 42v output connected to c and then disconnect the output from c to the stepper motor i then get 42v instead of 1.5v...so im thinking there may be a short in between the 42v output to the c driver board and the output connector to the stepper motor...

i know its a bit confusing since you dont know the application but to me i may have a bad driver board or a bad stepper motor

the driver board outputs to the stepper motor...

i guess i will have to do some further troubleshooting...my initial idea is that the L298 chip on the driver board could be bad...i may have to do some swapping of abc boards to narrow it down to the driver board or the stepper motor issue....at this point i really dont know becasue i really dont know what caused the main fuse to blow in the first place...maybe this is all related but i dont know....im not sure if its possible if the driver board failed if that would blow the main 110v fuse or not...

man this is so crazy...electronics can be very difficult troubleshooting especially for me since im not really into electroniocs

[sam_sam_sam]

Re: Dc power supply in cnc not working

If you are loosing the power to the stepper motor board then check the the mosfets for shorts this a common thing that happens to stepper controllers this what is bad about when power supply do not put fuses to controller boards

Show a picture of this board that goes to 1.5 volts when plugged into the power supply

[shelby5041]

Re: Dc power supply in cnc not working

well my stepper driver boards do have 2A fuses on each of them and they did not blow

this is just all so confusing as i may have multiple issues going on at same time or just a fluke that occurred

there is no reason any of this should have happened as the last time i used the machine it worked fine

a main fuse blowing and stepper driver board failing at this moment in time just doesnt make sense.and both may or may not even be related to each other....which makes it even harder to troubleshoot..although out of the 3 machines i already have had to repair 2 stepper driver boards all for same reason...failed L298 chip which is the output power/direction to the stepper motor

these machines are very old about 25 years..on the last 1 i modified i did blow a driver board just from playing around with moving each axis...apparently these L298 chips are just failing due to age...

i still need to find out why the voltage is going to 1.5v when i connect the c driver board to the stepper motor..maybe the stepper motor is bad.although ironically..(the stepper motor that is connected to the C board is new it was replaced last year due to it failing and never even used it other than testing) so it failing would make no sense at all...unless the almost failing driver board initially caused the stepper motor to fail or visa versa and now the driver board decided to fail completely?

see photo i had from my other machine (all 3 machines are identical in electronics design and parts) ..in yellow are the 3 identical stepper driver boards that receive 42v from the big cap board. and as you can see each has a glass style fuse in the 42v input circuit before the board not within the board.

im sorry i know this is hard to follow ..i talk in circles a lot lol

[sam_sam_sam]

Re: Dc power supply in cnc not working

What is the resistance for the power supply wires to the stepper board

[shelby5041]

Re: Dc power supply in cnc not working

i do not know im not at machine anymore

i gave up for the day

What i dont understand is why the 1 output connection to the stepper motor on the 1 stepper driver bosrd s causing all 3 boards to lose 42v...what could csuse this?

maybe its not a driver board failure? i checked the wiring to the stepper motor and nothing looks bad

The other 2 times my stepper driver boards failed ...they did not affect voltage to the other boards.

[eccerr0r]

Re: Dc power supply in cnc not working

All the boards are connected in parallel, one is a short, electricity goes through the path of least resistance... everything goes down.

Again as said in the first few posts, you need to fix this short first, should have looked into this before looking into the LM338. You could use an external, current limited 12V PSU to help debug.

[shelby5041]

Re: Dc power supply in cnc not working

at least i got the big cap repalced and seems to be working ok

see the connection in red....thats the connection that causes to lose 42v at ps output

very odd

hope to figure it out..may be something odd yet simple.

[shelby5041]

Re: Dc power supply in cnc not working

thanks essr...im not smart that why im in here looking for help and yes you did mention a shorrt a while back....i am at a standstill for now...i have no idea what to look for now.and have no idea what to do next other than swapping boards etc to see if it is indeed a driver board issue but that wouldnt tell me which componenet...althought the L298 chip is what fails most often ...as i said before i already replaced 1 L298 chip on the other driver board on this machine last year...

essr...do u think if the driver board shorted out wouldnt that have blown the fuse that was in the 42v circuit going to the driver board? or not necessarily?

the main fuse on the machine blew.

i still have no idea why the main fuse blew on the machine..and even though all of this happened at the same time ii really dont know if these issues are related.

[eccerr0r]

Re: Dc power supply in cnc not working

Are these 42V steppers? I'm not familiar with industrial machinery.
Does the machine otherwise work with that one stepper disconnected?
Can you measure the resistance of each of the windings of the motor and compare to other motors?
Is the faulty axis the same as the one you were working with the potentiometer?
Can you swap axis motors to see if the problem goes wit the channel or goes with the motors?

[shelby5041]

Re: Dc power supply in cnc not working

the stepper motors are orig other than the 1 i replaced....i beliefve most hobby nema23 stepper motors can handle up to 48V..

the stepper motor connected to the suspect driver board is new..repalced it last year ..and never used machine.....after that other than testing .

no..the potentiometer was for a diff board on the machine that controls spindle speeed...not related at all

i did not try to operate machine without the 1 board connected...will try toomorrow

yes i can try swapping boards..thats what i have done in the past to troubleshoot these machines....i just called it quits early since i got frustrated...and i planned on doing board cable swaps tomorrow

[eccerr0r]

Re: Dc power supply in cnc not working

Are you sure about that? Stepper motors have a limit of how much current the windings can take before it blows. If you feed 42V to a motor designed for 12V it will get very hot and draw a LOT of current. You need to match the original.

There should be a current, voltage, and resistance rating - usually at least 2 of 3 of these - for each stepper motor. If you don't match them you can fry things.

[sam_sam_sam]

Re: Dc power supply in cnc not working

Show a picture of the original stepper motor and a picture of the replacement stepper motor I want to see the data plate and please make sure that you can read the data plate clearly

I want to expand what eccerrOr was saying in his post above not all stepper motor will work on all stepper motor controllers if you cannot find a exact replacement stepper motor then what you might have to do is replace all three and use a different stepper motor controller ( if all three stepper motor use the same stepper motor controller)

What is the part number of the stepper motor controller ic chip it is the one that has a bunch of pins on it that is on a heat sink

shelby5041 I have a engraving machine that uses stepper motors and uses a nano controller to control them and thought the same thing however this is not the case when I want to change one of the axis to a different type of setup the stepper motor did not turn with the stepper motor controller and would turn it just twitch back and forth but would not turn so had another stepper motor but this one the data plate did not have the information that was needed to be able to match it correctly so I had to buy three stepper motor so they would all match

Why did you have to replace the the stepper motor what was wrong with it please go into some detail about this issue with it and do you still have the stepper motor in question

Do not swap boards around at this point because if the stepper motor is the wrong type it will destroy the stepper motor controller ic chip

[shelby5041]

Re: Dc power supply in cnc not working

hi essr ..replacement stepper is 3A 3v steppers ....the stepper drivers is what receive the 42v.... .the stepper driver main chip on the heat sink is L298 ...all i know is i have used these stepper motors in several applications and they work fine..industry standard .i used 2 of these in the other 2 machines and no issues......the stepper motor driver controls the current and voltage ..the stepper motor does not receive 42v...i believe the stepper drivers only feed 1.5 or 2A...

the replacement stepper motor is same physical size nema 23 and is more powerful than the 25yr old orig..

i do not believe this is not an incorrect stepper motor issue .as i said..i replaced 2 stepper motors in these machines previoulsy with this same stepper motor model with no issues


bottom line is something caused the main 110v fuse to blow and i dont know what.

is it related to the no 42v issue ? i dont know
is it related to the potentiometer i was trying to install? i dont know
was it a fluke? i dont know

the main fuse has not blown again since i replaced it and i have powered machine on and off several times since then

the potentiometer was disconnected from circuit prior to replacing main fuse and i have not tried connecting it back....i need to deal with the no 42v issue first.

i was going to post this is a cncforum like cnczone but i figured since originally i thought this was a power supply issue i would try here..but after my findings yesterday it seem like this may not be related to the power supply at all.

i will continue troubleshooting later today....i will try connecting the suspect driver board to one of the other orig stepper motors and leave the suspect motor out of equation for now as you recommenbded....

[shelby5041]

Re: Dc power supply in cnc not working

the stepper drivers on these machines use the L297 and L298 circuit

i have never had to replace the L297 but i have had to replace 2 other L298 on this machine and other machine

here is a link to what l297 and l298 are

https://www.apogeeweb.net/circuitry/...or-driver.html

[eccerr0r]

Re: Dc power supply in cnc not working

A fried L298 could be possible and explain shorts.

[shelby5041]

Re: Dc power supply in cnc not working

Updste...i was pretty confident that stepper motor good so i connect suspect stepper to othet stepper driver and it works good

The other 2 stepper motors work fine as long as the bad driver board is not connected to motor

So im pretty sure its a bad driver board bad L298...like i said i think these are failing due to age and or environment...unheated garage can get to -10f some winters although specs say L298 can handle up to -40C so temp should not be issue..prob just age issue

Here is a pic of board i just remove..im going to replace the L298 today..i bought several last year knowing this could be a constant issue since machines are so old..these boards are obsolete and can not be obtained anywhere..they can only be repaired..thankfully they are old school and all the componenets are replaceable....

and dont laugh at how i replace the L298....i use an odd technique....since these boards are obsolete not avail i cant risk ruining it and since desoldering the multipin chip is not easy for me i just cut legs carefully with a small hacksaw blade and resolder in the new one on top of the orig legs...it doesnt look good but it works and reduces my risk or ruining several pads etc...

[eccerr0r]

Re: Dc power supply in cnc not working

Not much to the board in terms of what can be swapped - need to swap out the melted L298 or the whole board. Indeed the melted L298 will explain the short.

[shelby5041]

Re: Dc power supply in cnc not working

eccr is it possible that if the L298 is fried as i suspect....could this have blown the 110v main fuse? and not blow the 42v inline fuse to the driver board?

or would it not be related to blowing of the main fuse at all?

i beleive both fuses are 2amp but not sure if they are identical specs slow blow fast blow etc