[s00073055]

hello all
i have a 160 low voltage alarm on my 1994 hass vfo machine and on the second page of the diagnostics it shows a DC bus 0 volts. this has me totally confused i bought the machine from a workshop and seen it in operation with no problems. my input voltage is on the correct section of the transformer. any thoughts on this would be great thanks.

[Machineit]

Get a good voltage meter and check two things. One, that all three lines are hot. Second, check the actual voltage on each line. Just because you are supposed to have say 220 volts service, it may be much lower. If they check out OK, make sure you are on the proper tap terminals for your voltage.

Good Luck---Mike

P.S.: Also make sure the previous owner did not have it set up with the high voltage option---440 volts I believe. They could have been running 440 three phase.

M

[Haas__man]

Once you have checked that in coming power is correct - You are probably looking at a faulty servo distribution PCB.
The PCB converts 230VAC to 170VDC.
The PCB is located near the centre of the electrical cabinet about half way down - it has two big blue capacitors on it.
Check with a meter that you have in coming power to thte PCB, then check to see if you have DC power coming out to drive card units. There is a red LED near the centre of the PCB that is usually on when the machine is on.
If the red LED is on - then be very careful when checking - Large capacitors/High DC volts can be very dangerous.

Hope this helps.

[s00073055]

thank's guys for the replies, the power is coming to the SD pcb but no output to the cards and the led is not on. i also looked at the led's on the main processor board and the HALT led is on(not as bright as the others) is the main PCB controlling the SD pcb?. this machine was stored for a year with myself before i tried to start it up and the 3v back up battery is ok. i have the high voltage option and three phase supply and would be happy we have that connected correctly.

[Haas__man]

The halt light should be on (but dim) - this is normal.
I would recommend you order a new servo dist pcb from your HFO. The replacement is an upgraded model. Alternatively you could remove the PCB from the machine and see if you can get it repaired.

Hope this helps.

[s00073055]

Thank's for the help. regards Denis

[gulliver22]

The halt light should be on (but dim) - this is normal.
I would recommend you order a new servo dist pcb from your HFO. The replacement is an upgraded model. Alternatively you could remove the PCB from the machine and see if you can get it repaired.

Hope this helps.

I'm having a similar problem on a 1994 Haas VF2. At first it would let me clear the alarm and I could use the machine. But now it wont let me clear it. The diags page shows 100 volts on the DC buss. Does one or both of the big capacitors start to fail and cause this problem? The 2 lines (black/red) going to each of the servo cards show no voltage on all of them. Is this where they should be reading 120 volts?

Thanks,
Mike

[s00073055]

I'm having a similar problem on a 1994 Haas VF2. At first it would let me clear the alarm and I could use the machine. But now it wont let me clear it. The diags page shows 100 volts on the DC buss. Does one or both of the big capacitors start to fail and cause this problem? The 2 lines (black/red) going to each of the servo cards show no voltage on all of them. Is this where they should be reading 120 volts?

Thanks,
Mike

Hello is the red led below the two big capacitors lit when the machine is on, if not check the resistor under the led for a open circuit this was the cause of my 160 alarm it may be something else but check this first hope this helps.

[gulliver22]

Hello is the red led below the two big capacitors lit when the machine is on, if not check the resistor under the led for a open circuit this was the cause of my 160 alarm it may be something else but check this first hope this helps.

The light does come on. I'll check the resistor anyway. Thanks.

[gulliver22]

So I figured this out after removing the board and tracing the route visually. Turned out the big resistor (looks to be a 2W size) that drops the 165 or so DC voltage going to the trim pot was failing. It's supposed to be a 22,000 ohm resistor, but checking it showed it was at 55,000 and climbing. Because of this it would supply too low of voltage, and the trim pot at its lowest resistance would still result in too low of a voltage reading to the controller.

If you receive the 160 low voltage alarm, here's some steps to help diagnose it. WARNING! There are dangerous voltages inside the cabinet that can KILL you. And/or you can destroy expensive electronics. If you're not comfortable doing this, call a qualified tech.

First verify if you have 165 volts, within say +- 10 volts (you can check at the rectifiers or at the top of these 3 resistors to a chassis ground). If is is within range, then power down the unit and let the capacitors drain (prob 5-10 minutes, voltage should be zero at the resistor top) then check the resistance of the resistor (far right of the 3 big ones) right above the right trim pot. Should be around 22,000 ohms. If it's significantly off, then it needs to be replaced. $1-2 part, whereas the board is about $500 after trading in your old board.
If the resistor is in spec, then check the trim pot, minimum should be 0 ohms, maximum setting should be 10,000 ohms. If that is okay, then either it needs to be adjusted or the downstream resistor is bad (should be at the bottom of the row of horizontal resistors under the trim pot). Pm me if you have questions.