[A.A]

Hello everyone,
I powered ON my series 1 today after more than 2 years and found that neither the Z axis nor the Yaxis is working fine, these motors are producing Hummmms and the shafts are not turning around. Only the x- axis was working fine.
I tried my best checking any disconnected wire but nothing came out. In the end i inter changed my X and Y SMD boards and as a result i lost my X-axis toooooooooooooooooooo....
Should i replace all the transistors ?

[timprebleco]

A.A
In my pervious post I said I am a novice. When your machine quits working you have to learn a lot quickly. I have found a guy that has a lot of experience with these machines (is running 5 of them daily) and has helped me a lot.
Our experience is that not all of the transistors die at once, just one at a time per axis, in each bank on the the heat sink, after you pull the ACC and the 3 drive boards. There are 3 sets of transistor banks with 4 transistors each in them. That is probably the problem and only one per axis is probably bad. They are about 4.00 each from Newark ,Transistor #2N6547. Make sure you have heat sink compound for re-assy.
The best inidcation is that the machine will step in the jog mode but nothing else.
You can check them in the machine and know if they are bad by using a meter with a diode check function. Mine came from Harbor Freight (Model#P37772) for about $40.00 A name brand meter is probably is about $300.00
Power off the Machine!!!!!!!!
Turn the meter to the diode check function.
Place the Black common probe on the top large green wire terminal (There is a jumper strip tying it to the next lower terminal) and place the red probe on the lowest small wire terminal you should get a reading of about 450-600 it is good. If you have continuity or the meter reads 1 it needs to be replaced. Work your way up the small wires if any read low less than 100 replace it. Moving up to the larger wires in the terminal strip (common test lead still on the top terminal) you should get a reading of one, but no contunity. If you get a larger reading like you got on the smaller wires it needs to be replaced as well as the polarity has been dammaged.
When replacing them be carefull not to lose the mounting screws into the wires at the bottom. I have heard they can cause probles down there.
I bougth some extra banks from a freind so I can replace the whole bank at once and fix it later. On one bank they had installed 4 sockets to plug the transistors into.
Those are nice!
With those you do not have to remove the whole bank. Newark has them for about 10.00 each. I found some at a local surplus store for .25 each. The next time one goes out I will be installing the sockets. This takes your down time to about 10 min instead of the hour and you do not loose the screws.

Check your incomming voltage to the machine. Mine was high from the phase converter 255 v. I belive that was my problem. I have installed two buck/boost transformers droped the voltage to 235 v. and have not had a problem since. My electric was really flickering during that time as well. I think I just had too much power and surges coming into the machine.
I hope this helps, If you need any thing else just let me know.

[A.A]

Thanks timprebleco for such a detailed reply i have followed your instructions and found one transistor blown for all axis. I replaced those transistors and my X and Z axis are now working fine. Y axis is still not working i checked the current for Y axis and it came out to be 13.5 Amps DC . Where as X and Z axis current come out to be 8.2 Amp DC. The Y axis motor can be easily rotated when powered on i.e it do not resist like other working axis.

Any possible solution for this problem ?

Regards

[machintek]

Current is adjusted by the ACC board. Current that high should blown the fuse for that axis. If current is that high, and the motor turns by hand, the current is going somewhere else (dead short). Do you have insulators beneath each transistor? Do you have insulators (plastic) on the screws? I had one case where the customer lost a terminal screw, replaced it with one just a bit longer. Just long enough to grab the terminal tight and also bottom out on the chassis of the machine causing a short. That was a nice one to find!

George

[A.A]

George,
I have rotated the P2 potentiometer for Y axis on ACC board to both extremes i.e clockwise and counter clockwise, but the current do not change. I have double checked every transistor and diode of Y axis and every thing appears to be OK. I have cleared even all the dust particles near the power transistors and diodes and also checked the heat sink with every transistor for continuity . Don't know how to get out of this high current problem.

[HillBilly]

Here is a simplified drawing of the drive. The fuse supplies positive to the step motor. The four transistors on the heat sink work like switches grounding the windings and completing the circuit. Like George said the power must be going somewhere.

Power off pull wires Y1-4 off the terminal strip inside the heat sink door and insulate them, power back on and check current again.

Darek

[timprebleco]

A.A
You are at a place where I run out of experience. I have not had an instance that the motor would turn free under power. Sounds like you are getting help. Keep us posted as to what fixes it.
Thanks,
Tim

[A.A]

Dear All,
I have found one Y axis transistor with broken insulation sheet from the edge. I hope that it will be the only reason for such a high flow of current. But let me buy and replace a new insulation sheet for that transistor.

I'll update you all about the end result.

[A.A]

Hello,

I finally got x and z axis working fine after transistor replacement , but the Y axis after working fine for a few minutes blow a transistor again.
I want to ask you people that this problem could be because of wrong wiring of K8 signals with mach3 ? but this problem is only for Y axis?

I have checked each and every transistor on SMD board of y axis with a multimeter and all of them appear to be OK (without supplying 24V). and same is the case with ACC board Y axis transistors.

[HillBilly]

with power off pull the SMD board for Y axis. Insert the current meter in place of FU13. Power on, enable drives and measure current.

You should see no current as all the heat sink mounted transistors will be off.

Darek

[A.A]

Hi HillBilly

I have checked according to your recommendation when the Y SMD board is at its place the current flowing through it is exactly 8.2 Amps and when the SMD board is removed there is no current flowing through the y axis fuse i.e. FU13

and one more thing Darek from one of your previous posts i have checked each and every transistor of Y SMD board after supplying 24 Volts and all the ON- OFF sequence came out to be OK.

[keebler303]

I haven't had the need to do anything other than replace transistors but it may be helpful for you to dial down the current a little more. I was having problems with blowing transistors and after turning down the current a bit (~7.5 A) I haven't had another problem in the last 2 years or so. It may also be helpful to turn it wayyy down so you can test things without blowing a whole bunch of transistors. Everything should still work, it just won't have as much power.

Matt

[HillBilly]

Excellent advice Matt, I have done this before for trouble shooting.

A.A. the 8.2 amps would indicate the ACC is doing its job. There should always be two of the heat sinked transistors on. The ACC board monitors current just like your meter in place of the fuse and adjust the current accordingly. If you have a bad connection somewhere one transistor can be forced to carry the full current, this usualy blows that transistor.

Check the connections in the motor, the integrity of the wire and the connection inside the back panel. These are the most common places for trouble.

Darek

[A.A]

Thanks Matt and Dark for advice i reduced the current to 7.2Amps this time and then tried to move the y axis motor but still the same scene happened and one transistor different from the previous one was blown.

Please tell me how to confirm that my y axis motor windings are OK ?

On my behalf i checked the connector strip terminals labeled Y1,Y2,Y3,Y4 and Y5 the resistance between the windings are as follows

Y1 - Y5 = 1.1 Ohm
Y2 - Y5 = 1.1 Ohm
Y3 - Y5 = 1.1 Ohm
Y4 - Y5 = 1.1 Ohm

One more thing i would like to mention here is that my X and Z axis motors are the most popular series 1 motors that is they are covered by Heat Sinks and the Y axis motor is without Heat Sink. I will upload its picture soon.

The resistances for X and Z axis motors are 1.3 Ohms for each coil.

[kewl_cat]

OK, here is my two cents. I used to blow transistors quite often. I think I could change a transistor in record speed. I asked numerous questions on this forum and received good advice. I checked voltages, replaced fuseholders and did everything as advised as well as I could understand. I even went to a more robust transistor in the MJ series but nothing really seemed to help. I pm'd Hillbilly and he referred me to a post on checking the SMD board as I think you mentioned that you did. All my transistors on the bench test switched on and off as they should. But on checking the output on the case of the output transistors there was always one that had about 1V higher than the rest. When I put that same board in the machine and stepped the motor .01 at a time and there there was always one wire that would come up higher volatge than the rest. This took hours for me to figure out but there was one resistor going bad on the SMD board. It was losing its resistance and that output transistor was receiving too much voltage. It was the r43 or r44 resistor I think. The machine might run a day or a month without blowing a transistor but it would always die at the worst time. Since replacing the resistor (at 5AM) there has not been 1 single failure. Runs 8-10 hours a day 6 days a week. Basic electronics but it took me years to figure out. (nuts)
Worked for me, hope this helps.
-r

[A.A]

Thanks kewl_cat for your such an experienced advice, but the problem in my case is that the transistor blow as soon as i replace the fuse for y axis. It do not give me any time to play with it for even some seconds.
The voltage that i observed for Y SMD board is 0.5 V when ON and off course 0 V for OFF state. and these readings are taken from the final stage transistor of SMD boards i.e. Coin shaped transistors.

The only new thing i observed today is that the diodes mounted at the back side of transistors are turned black for y and z axis where as for the x axis these diodes are shining like new zener diodes. I am unable to read the numbers written on these diodes. can you tell me what should i do to them ??????

i have attached some pictures that i have taken from my mobile today. sorry for poor visibility. one picture also shows my y axis motor.

Now my problem is that my ACC board is working fine + my SMD board comes out with all transistors OK + i have exchanged my reactor with the Z axis reactor + my motor is giving correct resistance values + New transistors replaced + All Y axis diodes are OK. but still my axis is not working

[keebler303]

A.A

Is it the same transistor which is blown every time or does it vary?

It seems your problem has gotten past most of our experience.

Good Luck
Matt

[kewl_cat]

The diodes are 1N4003. Make sure you check the diode every time you replace a transistor. When I was struggling with the machine I replaced them all. THey are cheap. I hope you are not saying that you install the fuse while the machine is on. I always power down before removing or installing fuses.
On my good x axis the dc volts on the output transistors were 6.3-6.5 & 9.3-9.5. Anything above that proved problematic. Are you bench testing the smd boards according to Hillbilly's post? I use a 18V power supply from some long ago electrical device. Are you checking the voltage at the bottom of the cabinet where it goes to the motors? That is where I got my 6ish and 9ish volts for the on & off states for the motors.

[A.A]

Matt every time there is a new transistor. but only one out of the four is yet not changed.

kewl_cat i have checked all the diodes and they are responding well on the multimeter.
The voltages which i told you in my previous post were of those final stage transistors that are mounted on SMD board(on flat metal plates). I have done bench testing totally according to HillBilly's post after supplying 24V to the SMD board and the 0 and 0.5 Volts for OFF and ON states respectively were observed during bench testing the SMD board

I have not yet checked the voltages at the bottom of the cabinet from where it goes to motors, but today i will check them.

[A.A]

Hello Everybody,

Today i once again tried to find the Y axis fault in my machine. i have decided to replace all the diodes of my machine.
The most important thing that i observed today is the voltages across the Motor wires i.e. I measured the voltages across the Y1,Y2,Y3,Y4 with reference to Y5 for my Y axis motor and compared these voltages with the X and Z axis motors.

the voltages for Y axis are as follows

Y1 - Y5 = 1.5 Volts
Y2 - Y5 = 0 Volts
Y3 - Y5 = 0.9 Volts
Y4 - Y5 = 0 Volts

for Z axis

Z1 - Z5 = 4 Volts
Z2 - Z5 = 2 Volts
Z3 - Z5 = 0 Volts
Z4 - Z5 = 0 Volts

and for X axis

X1 - X5 = 2.5 Volts
X2 - X5 = 0 Volts
X3 - X5 = 2.5 Volts
X4 - X5 = 0 Volts

I think that only X axis is responding well. I need your suggestions and any solution if possible.

Waiting for your response.:drowning: