Okuma VAC type A spindle drive problems

I have a 1991 Okuma lb15 with a 5020l control. For the last several weeks I have been getting a 110 A SDU Alarm. Sometimes the machine would run for 4 hours, sometimes for 30 minutes, or sometimes only for a couple minutes. It has finally reached the point where the machine won't come up at all and just alarms out:drowning:. According to the LEDs on the drive it is experiencing a motor overload or a heat sink over temp. I tried using a jumper across the wires that connect to the temp sensor on the heat sink and the same thing on the spindle motor overload, but neither of those helped. I have spoken with techs at Hartwig Okuma and they seem to think it may be a bad top board on the spindle drive. I am open to suggestions or if anyone knows what component(s) on these drives commonly fail please let me know. Any help will be appreciated.

Check all IGBTs on the spindle drive unit first!

Thanks for the advice. I'll check those. I've had those go bad on a Fanuc drive before.

what led's on the drive are on when it alarms out with the 110 alarm on the control?

Thanks for your reply Old Timer. The leds that are lit are: power, m2, 1, and 2.

Heat sink and motor overload alarms. sounds like base unit is getting how. make sure the fans and fins on the back of the drive are clean. But it may be too late.

The fan is clean and working. The cooling fins are also clean. When you say it may be too late, what do you mean? What components on the base unit or heat sink could be damaged to cause this problem?

I swapped the base unit with a known good one and it made no difference. That leads me to believe the problem is in the top board. The board is a e4809-045-084g. The drive is a VAC type A D8-A. If anyone has an extra board or complete drive they would like to sell let me know.

Apparently, these drives are obsolete. The replacement is a Vac 5 D8 from Okuma at a cost of $13,518! Ridiculous. This will probably be the last Okuma that I'll ever own. I guess I'll have to send the drive out for repair.

Check out these guys

Did a board swap for mine at around $3400

Okuma:VAC-1 D8-A

I think I may have found the problem. If you're looking at the board as it hangs on the drive there's a heat sink at the top right hand corner. Just to the left of the heat sink is a 35v 120uf capacitor and a diode directly under it. The capacitor had leaked out and got electrolyte all over the diode, so I removed them. With the capacitor removed, and only in certain light, you can see a trace connection on the top side of the board between the cap and diode. I checked it and it read open. I ordered some new capacitors and will put one in when I get them. I'll also have to solder in some kind of jumper to take care of the damaged trace. What clued me in was, there is another 35v 120uf capacitor at the bottom of the board.(next to cn3) I checked that capacitor and it measured 260uf instead of 120-130uf. It was somehow in parallel with the other 120uf 35v cap, which I discovered by checking continuity between the positive terminal of one to the other and then the negative terminal of one to the other. Sorry for the lengthy post, but if this works out I want everyone to know. I'll update after I make the repairs.

Well, it's running. I soldered in a new capacitor and a used diode from another board and soldered a jumper from the cap to the diode on the back side of the board. By the way the capacitors I mentioned in the previous post ARE supposed to be in parallel. It was the damaged trace causing the problem.