Z axis is generating 160 low voltage alarm

[fastfrank]

Greetings All,

This is an outstanding site!!

I have a 1994 VF4 running off of a 30hp Phoenix converter with the leads in the proper tap on the transformer (all 3 legs fall within tap range) and between 115VAC to 125VAC on 94, 95, and 96 like it says on the transformer. Also I am reading 167VDC (I believe that to be good) on all 4 drivers coming off the servo distribution board. The CRT (diagnostic, 2nd page, says 144 volts (I believe it is looking for more like 145 to 175). With that, when the Z axis is rapiding, the 160 alarm hits.

I'm not sure why that if I have 167VDC on the driver, why does the diagnostic page say 144VDC? Also on the drivers, 3 say XYZ Axis only, and the last one (A Axis) says for A Axis only 15A. This makes me scared to swap it with the Z.

Does anyone have any thoughts??....Please.

Thanks Men

[Greg 24]

My dad has a 96 VF3 & had a very similar problem a few weeks ago. He had Haas come in & take a look at it. His machine was alarming in Z axis as well, but while he was drilling holes (1/2" in diameter). They adjusted a board for the DC Bus Voltage & it took care of it. They did this twice & it runs fine now. You could swap out your Z axis card for the Y or X axis cards. If the problem goes to the new axis the I think that your card might be bad. If the problem stays on the Z axis then I would think that it might be broke wire, Z axis motor. Hope that this might help you.

[Haas__man]

Ok,
As you have already said the A axis card is different to the X Y and Z cards. They are different and cannot be swapped. Swapping them would be very bad.
As for your problem it could be fairly simple:
It could just be the anologue to digital display potentiometer that needs adjusting. If you look at where the four drive cards are, look just to the right of the A axis drive and you will see a PCB with two large blue capacitors on it. This is the servo distribution PCB. Roughly in the centre of this PCB should be two or possible three small blue components with a white or gold screw (I should say at this point that you should be very careful here, wait until the high voltage LED has gone out before touching this, there is still power on this PCB even when machine is isolated). So, these three blue components - one of them will be labelled A-D. If you adjust this (by turning the screw) then the value on the screen should change - this does not change the actual machine voltage, just the displayed voltage on the screen. You should alter this until the voltage on the screen matches the voltage on the drive pcbs.
If turning the screw makes no difference then the problem is still very likely to be with the servo dist PCB and you should probably get Haas to replace the part. The new part is an updated version and you should not see the problem again.
Hope this helps.

[fastfrank]

Greetings

Both of you guys are making good sense. I have been trying not to contact a factory outlet because I'm paranoid they might highly frown on machine owners repairing PCBoards. I replaced the 2 small capaciters on the servo dist board based on one of the threads on this site. I reinstalled the board and saw no differance...back to the drawing board. I then noticed the 3 resistors above the 3 pots you are speeking of were fryed. I had them replaced and thought I would be good to go. The board was reinstalled and when I turned the power on at the control I went to diagnostic to check the DC buss voltage and I saw it at 157 and dropping fast (servos were off). I went back to the cabinet to have a look and the new resistors were smoking (!@#$%^&*). So I decided it was time to call Haas. They are saying I probably could have fixed it in the beginning by adjusting the A_D pot. He told me to unhook the black and white wires on the Z axis servo which go th the Z Axis motor and get an ohm reading on them. He said the motors were 2.5 when new. If it is less than that it may have carbon build up. Remove the brushes and vacumn the motor the best I can and use some clean compressed air gently. I had to stop and pick up the kids before I could check the motor. The kids are in bed and I'm going to the shop to do the motor test.

Not sure about my newly burned resistors....hopefully the Haas guy can steer me in the right direction in the morning. Also the Haas guy seemed to be fine with me repairing (trying to repair) the board.

Thank You for your help and I'll keep you up to date.

[fastfrank]

Greetings once again

I am asking for someone to please take a look at the 3 resistors above the 3 light blue pots on the servo dist board to figure out what colors thay are. Mine are burned and the color bands are hard to read. I want to replace them with the proper resistors.

Thanks

[Haas__man]

I have also had similar problems with those resistors. I do not know what the cause of them smoking is, but I replaced them with the correct resistors and they still burnt out(but I do not currently have the colours of the resistor for you unfortunately). I would still suggest that you get the upgraded PCB from Haas.
The black and white wires that you are checking - if you do an Ohms check from black to white all you are really checking for is that the motor cable is good, that the windings in the motor are good and that the brushes have a good contact on the motor com. It won't check for carbon build up. To check for carbon build up you need to check from one wire to earth (should be a high Ohms value, more than 500Kohms.
Hope this helps.

[fastfrank]

Greetings

Ok I'm saying (crying) UNCLE!!

We took a guess at the colors and replaced the resistors. We must have guess wrong and thats when they were smoking. We took another guess and replaced them again. This time I have no DC Buss Voltage at all.

I bit the bullet and ordered a new board from Haas. About $500 with shipping.

Thanks

[fastfrank]

Greetings

Installed new board and all is well.

It is easy to get caught up in the temptation of a cheap fix. I only spent about $12 bucks on caps and resistors but in the end I got killed money wise with all the time I spent messing with it.

Just food for thought.

Any way, my first experiance with the site was great!!

Thanks

[DaOne]

Mind reading those resistor values not that you have a new board in place? Might be a good idea just in case they ever fry again. I would like to have that info if you don't mind sharing it.

[fastfrank]

Greetings DaOne

Please be fore warned that this is only a guess since the new board has been updated and no longer has these resistors and the old ones were badly burned. I/we think they were 27k 2 watt. We may have been better using 4 watt.... I don't know enough about electronics to say. I could visually see the were burned and thought I would give replacing them a try.

Sorrry, I don't think this helps much.