HAAS VF-1 Over Voltage alarm at 100% rapids

Hi all,

I'm running a 1991 HAAS VF-1 which has been brought back from the dead a few times. It's been running well lately now that I have squashed most of the problems, but there's one issue still remaining: When running at 100% rapids, I occasionally get an Over Voltage alarm (119 IIRC). This only happens after running for a little bit and so far as I can tell the incoming line voltage is OK. The DC bus voltage usually sits on the higher side but not outside of the limits.

I've been running the machine for a few months at 50% rapids and it does great, but I have been doing a fair bit of 3d machining and some production work lately and the faster rapids would save me a not-insignificant amount of time. Has anyone seen this before, and do you have any suggestions?

Some brief searching turns up results pointing to the brake resistors overheating, caps going out of spec, and bad control boards. I'm hoping it's one of the first two or something even easier to fix, but I'd like to hear from some folks directly instead of mindlessly google-fu-ing my way through this.

I am working towards a newer machine eventually, but I am currently maintaining a day job and doing job shop work in the evening so I'm stuck with what I've got for a little while longer, especially if I first pick up a CNC lathe instead of a newer mill.
I'll be at the shop this evening and I can check exact voltages and temperatures if needed.

Thanks in advance!

Presumably the regeneration when the servos stop is driving the voltage too high. The Power Monitor board next to the servo boards has a potentiometer labeled CLAMP. That controls the driver for the servo voltage dump resistor. Check the diagnostics to see what the servo voltage is during the rapids.
Also check the OVER VOLTAGE potentiometer is setting off the alarm at the right voltage. Check the manual for the limit. I think is about 190 volts.
Your dump resistor might be inside the cabinet next to the power monitor board and under the computer. I moved mine outside the cabinet like the later models with a fan to keep it from melting. No need for a heater under the computer.

I will take a look, thanks.

Double check the incoming voltage verses the transformer taps. If the voltage is high and the taps are set low then it could bring the DC bus too close the what the regen can handle. Even if the machine has been in place for a while the input power may have changed.

So it's set for 230V, which is correct for this building. However, the actual input voltage is 250V-253V! That would definitely put me on the very top end of the +-10% range.
Turned rapid back up. While idle, the DC bus sits at 184V and fluctuates a little when moving. At 100% rapids though it gives giving me a 141 Z motor Z fault. Not sure if that is related.

It's gotta be an input voltage thing. I reseated the encoder connectors and it runs fine. Ran the warm up program with a G00 instead of a G01 and gave it a workout. DC bus voltage ranged from 170VDC to 186VDC depending on acceleration or deceleration. Brake resistors seemed fine- Not glowing red or even noticably hot, even moving all 3 axes around quickly. I guess all it takes is another 3-5VAC plus an axis decelerating from a rapid to kick it over the 190VDC limit though. Going to talk to the power company.

npolanosky said:

So it's set for 230V, which is correct for this building. However, the actual input voltage is 250V-253V! That would definitely put me on the very top end of the +-10% range.
Turned rapid back up. While idle, the DC bus sits at 184V and fluctuates a little when moving. At 100% rapids though it gives giving me a 141 Z motor Z fault. Not sure if that is related.

Click to expand...

If you move your connections to the 260-244V taps you should be OK.

Pipes said:

If you move your connections to the 260-244V taps you should be OK.

Click to expand...

I wish I could, but I don't see that option. I only have 208 and 230v taps as far as I can tell.

npolanosky said:

I wish I could, but I don't see that option. I only have 208 and 230v taps as far as I can tell.

Click to expand...

That's strange for a Haas. Are you looking at the transformer in the bottom right of the Haas electrical cabinet?

Pipes said:

That's strange for a Haas. Are you looking at the transformer in the bottom right of the Haas electrical cabinet?

Click to expand...

Should look something like this:

Haas Paraline 4262 Multitap 26 195 Volt Input Transformer 1998 VF3 | eBay

His is probably an older machine like mine (1124) that has only two taps on the transformer.
You probably will have to increase the power going into the servo regeneration resistor through the Servo Power board potentiometer to bring down the voltage.

magno_grail said:

His is probably an older machine like mine (1124) that has only two taps on the transformer.
You probably will have to increase the power going into the servo regeneration resistor through the Servo Power board potentiometer to bring down the voltage.
View attachment 190465

Click to expand...

Yep, more or less exactly that. Any negative effects to sending more power to the resistor? I'm assuming there will be a little more heat, but I haven't had heat problems with them before. (Have heard of others completely cooking them)

Pipes said:

Should look something like this:

Haas Paraline 4262 Multitap 26 195 Volt Input Transformer 1998 VF3 | eBay

Click to expand...

Nope, that would be too easy.

Yes, you can melt them. I replaced mine with an Ohmite 225 Watt 50 Ohm mounted outside like the later VF's with a fan. My PC power supply has unused output leads.
The original is a Marshal 175 Watt 50 Ohm (4.5" long rather than 10" for the Ohmite).
Putting a heater right underneath the computer did not seem very bright to me.

Ok- I'm doing some other maintenance too, so I may see about installing a fan and adjusting the pot a little bit at a time. I'll mount them outside as soon as I can manage.

I'm having some spindle trouble too as of last night, but I'm going to create a new thread for that since it's unrelated.

I am right here in the same boat with you npolansky.
It has been one hell of a week at our shop.

1993 VF1. Same alarm #119 over voltage, first time was yesterday, did it twice. Today? Pffft, all freaking day.

Difference is mine alarms even when setting idle.

Was going to post my own thread but did a search first and found you're already looking for the fix.

Haas tech asked on phone was the dissipaters getting hot, (nope) and was line voltage good. THINK line voltage is good but after reading this post Im not so sure.

HASS tech is leaning toward the spindle drive ($4000) Rebuild on rush time $1700.

Hope it turns out to be something simple like already covered in this thread.

Good luck npolansky, hope it turns out to be something fixable and simple.


Just to make it a great week for us, big job in shop, CNC lathe CPU board took a dump..had to have Mitsubish fix it..$3500
Job moves to mill...mill takes a dump as described above. Job still due NOW.

Ouch- Yep, same boat. I think I'm going to have to clear out this week's jobs with things dialed back a bit and then I might have to take it down for a rebuild or a new cartridge depending on the rebuild time.

Problem with over voltage seems to be fixed.
I also was incorrect about model, its an 1993 VF2, not 1.

I have the taps like pictured in Pipes post #10.
Changed from tap 195/210 to tap 211/226 seems to have corrected our issue with the alarm 119.

Checked several times and for a period of time, my incoming voltage was - 214.4/215
Tech comes in this AM and checks incoming voltage at 210 volts checked for several minutes, I checked with my meter and got the 210 volt.
No idea why the 5 volt drop from yesterday. I was mindful of current draw to other equipment and even lights, none of that seem to matter while
mill was kicking out over voltage alarms.

Long story short, my incoming voltage was right at the threshold when tapped to 195/210
Any current bumps for what ever reason was enough to push it over the limit.

Shop power supply is sketchy at best. 480 to a 75 Kva transformer. This transformer powers, VF2 mill, Mazak lathe (49Kva draw on info plate),17" manual lathe,
wall plugs, lights and fans and that's just what I'm aware off at the moment.
Lights dim and some trip out when the manual lathe starts.
Slight flicker in lighting when Mazak CNC spins up or is in rapid movement. Its going to be addressed. Boss was told to expect to buy more drives and cards for the CNC machines now that they are being put to work steadily.

Last thing.
This thread basically fixed our machine.
This is why its very important when we have a problem to follow through with it on the thread and be as detailed as you can.
Threads like this on PM has probably helped a many of people get out of a jam and back up and running without loosing their ass for that month..or two.