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1996 vf-oe -4025L power distribution board issues

hend.engineering

Aluminum
Joined
Jul 30, 2019
Hi,
Very slowly getting to the bottom of a major problem with my VF-OE, mostly backwards steps but anyway...
Long story short, issue with drive amps has burnt out a track on the central board, fixed that but am curious about what voltages I should be measuring on the rainbow coloured ribbon cable?

Currently from blue to brown I have got 200v, nothing, 24v, nothing, earth and earth.

Does that tally?

If not, any ideas what they should be?
Pretty sure I had measured the blue strand at only 19v previously, but have mislaid my notes.

Thanks in advance,
Tom.
 
If the wiring for the servo Power Monitor board is the same as the VF-1 '91, the brown is ground, red open (on the PM board, tied together on the servo board), orange/yellow is 18 VAC, and green/blue is 14 VAC.
The two Power Monitor transformers are Paraline(?) 18/14VAC OEM or special.
The only high voltage on the servo boards is the 160 VDC, P8.
 
If the wiring for the servo Power Monitor board is the same as the VF-1 '91, the brown is ground, red open (on the PM board, tied together on the servo board), orange/yellow is 18 VAC, and green/blue is 14 VAC.
The two Power Monitor transformers are Paraline(?) 18/14VAC OEM or special.
The only high voltage on the servo boards is the 160 VDC, P8.

It's DC by the time it gets to 1995 by the looks of things, and the multimeter checks that out too.
Te transformer down the bottom then traces to a pair of discreet bridge rectifiers and then on to the ribbon cable connectors.

I've ordered a few and am hopeful that it's the cure but I fear the transformer has shorted to cause such a high output voltage.

Been flat out recently but will update when I've had a minute to play.

Anyone else got any ideas?
 
Got nowhere with the rectifiers, must have fried the transformer, new board in the end fixed it...£2 part, £350 dent in the wallet!
 
Sorry to dredge up an old thread, but I have a machine I'm troubleshooting with the exact same conditions as your original post, and knowledge on there old machines is getting sparse. My servo distribution board is outputting 176vdc and 21vdc through the rainbow ribbon to the servo amps. All references I've found point to AC power on the low voltage ribbon feeding the brush servo amps, but my machine (1993 VF0) has two small bridge rectifiers on the servo distribution card to convert the transformer output to dc. There are also the two large bridge rectifiers for the 160vdc supply as well. I'm quite certain there must be something wrong, as 176vdc does not seem right. Long story short, I'm curious what you found to be the proper voltage output on the rainbow ribbon cable when you replaced the servo distribution card on this machine....I'm hoping you still have it.

Thanks in advance for any help you can offer.
 
Sorry to dredge up an old thread, but I have a machine I'm troubleshooting with the exact same conditions

Nothing wrong with dragging up an old thread, particularly where it may help other and myself keep an old machine alive.

Since replacing my board the machine has mostly behaved itself and aside from a servo board going funny and only working in one direction I haven't had many issues since.
Very grateful for that too. The stress was killing me.

176v dc is about right, and that's what heads off to the servo boards. Rainbow cable wise I haven't looked at mine since.

Your voltages don't sound a great deal off but I couldn't tell you what mine are, long since forgotten. Could measure if you're desperate.

What faults or errors is your machine giving you?
 
My 160v dc bus is behaving itself, running about 156vdc. The 176vdc I'm measuring is in the rainbow colored ribbon cable from the blue to brown wires. Yellow to brown is about 20vdc. Those are the only 2 real circuits in there tracing out this board. That seemed to match up with what you had posted originally.

My alarms are axis overload or drive fault (161, 162, 163). To date, I have disabled all but each axis individually with the same fault on x,y, and z. I have cleaned the carbon out of the motors. And verified no short to ground, which I doubted since it seemed unlikely that all 3 axes would do this at the same time.

All my reading indicated 14 and 18 vac in the low voltage ribbon feeding the servos, however my machine seems to feed dc 20v and 176v through the ribbon. The 176vdc scared me, which got me looking for answers.

I hate to ask because I don't want to put you or your machine at risk, but if you think you can safely measure voltage from blue to brown, and yellow to brown, the info would be very helpful. If you feel at all uncomfortable please don't feel obligated at all....I do not want to be responsible for the harm of you or your machine.

No matter what happens, I'll post up what for me working to document it all for the next person in trouble.
 
I have and they referred me to some documentation in the maintenance manual for that year. Said documentation references AC power of 14 and 18 vac, which Im sure is correct for many models, however this version of the servo power distribution board uses an additional set of bridge rectifiers and smoothing capacitors to convert the transformer output to dc power. In tracing the board, I'm beginning to think 175 vdc to ground may be roughly correct. I've found a bad relay on my board that I'm going to replace. More to come as I dig through the board a bit more.
 
If you get an opportunity to take some decent pics and can post them up, I can help with things to check. Would need to be able to dialog a bit in PM about component Id's and such. I wish my Mech-cred were as strong as my 90's electronic efix-it skills. :-) There is a lot we can check and diagnose w/ just a DVM and diode checker, etc. Keep us posted!

I have and they referred me to some documentation in the maintenance manual for that year. Said documentation references AC power of 14 and 18 vac, which Im sure is correct for many models, however this version of the servo power distribution board uses an additional set of bridge rectifiers and smoothing capacitors to convert the transformer output to dc power. In tracing the board, I'm beginning to think 175 vdc to ground may be roughly correct. I've found a bad relay on my board that I'm going to replace. More to come as I dig through the board a bit more.
 
Haas probably figured out it is cheaper to change the servo board low voltage power to DC on the Power board rather than duplicating the components on each Servo board. Presumably, near where the ribbon cable from the Power board connects to the Servo board there are no diodes for rectification. Early boards had one diode, then two, then four.
Does your Power board have a potentiometer near the MOSFET that controls the current to the power resistor? The MOSFET dumps excess power into the resistor to control the high voltage.
I moved mine ('91) outside the cabinet and added a fan to cool it. Dumping all that heat under the servo boards was a bad idea.
 
It's a 1993 VF0, and it does have single diode 32-4070 servo drive cards. I'm working on repairing over of those as well that has 2 shorted mosfets which burned up the gate resistors, one diode, and one gate driver.

The reason I was looking at the distribution card was because I noticed a burned trace at the a-axis ribbon cable connection. Turns out, that burned trace dropped power to all the axis cards. While fixing that, found the shorted relay, which may have contributed to the burned trace.

I got this machine non-running in good mechanical condition, and it has been a rabbit hole of electrical issues, but slowly getting there. Right now I'm waiting another day or two for parts from digikey to go any farther.

On the topic of dc voltage in the rainbow colored ribbon cables, I've traced out the boards and it's interesting what they've done. I'm not entirely sure why, but after rectifying the transformer secondaries to dc, one of the two has it's dc- tied directly to the +160vdc bus by design. Essentially, if you measure dc power to ground it is 176vdc, but on the servo drives this is V+ for a comparison, and +160vdc is tied to V-, so it's seeing approx 16vdc. I'm confused why this was done, because by doing so 2 of the 6 pins in the ribbon are not used. No traces on the distribution board go to the green or orange wires at all.

I'll keep updating as I go, and post what I see when I get a few parts replaced and can power the machine back on safely. In the meantime, is there a good way to easily measure the motif pwm signal to make sure I'm getting output? I know it's reading the encoders, as I can get a following error by manually rotating the screws, but I'd like to verify it's sending a proper signal.

Sorry for the long post, and thanks for your help.
 
Single diode 30-4070 is probably Rev.D or earlier. Those MOSFETs were upgraded several times to keep them from blowing. Changes to the gate resistors with the MOSFETs. Rev.D had MTM40N20 with 330 Ohm gate resistors, Rev.K had IXFM50N20 with 68 Ohm gate resistors. I think the first boards had 30 amp MOSFETs.
The earlier Power Monitor used the green and orange wires for the 14 VAC and 18 VAC. Simpler to keep the cable the same.
Follower error is either from the motor not keeping up with where expected or from the motor and encoder directions are opposite of what is expected. In the servo parameter switches there is a setting for the encoder and motor. Try changing the values (0/1) to each of the combinations to see if the error goes away.
I hope you did not clean the carbon out of the motors by blowing in the brush holder holes. That would push dust into the armature which will not show up as a short on an Ohm meter but will with 160 VDC.
 
Thank you, I knew about the switch to the IXFM50N20, however was not aware of the change in the gate resistors. The mosfets are getting hard to find without going to an equivalent in a TO-247 package. The original mosfets appear available on eBay, but I'm wary of quality, so trying an IXFH50N20 instead.... Same MOSFET, just a TO-247 package. I'll make the swap to 68 ohm resistors as well. I had the MTM40N20 and 330 ohm Rev D boards.

Fortunately from reading a lot of prior posts, many written by yourself, I spent the time to mark orientation, disassemble, and clean my motors well. Thank you for documenting your journey which helped with that. Two motors had half worn brushes, which I reinstalled while I wait for new that I have ordered. Last testing, my following errors were gone after repairing the trace on my distribution card, but now I get immediate over current alarm when servos are enabled. I think this may be related to the bad relay on my board, which I just got tonight. I have tried disabling all but one axis and switching drive and encoder directions to no avail, but that was when I had following errors, which I now know was due to the drives not getting low voltage power through the burned trace I repaired.

Hopefully I get the time to solder a few parts on in the couple days to test.
 
I did a redesign of the servo board using surface mount parts, it could easily be 1/3rd the size. The limiting factor is the aluminum L bracket that serves as a heat sink and mount and the ribbon cables would have to be a little longer, all the same connectors. If one of mine takes a dump I will probably do it. The biggest expense is the board. I think 5" x 4.25" is the smallest practical size due to the connectors and fuses which take up a lot of room. $287 for four boards with silkscreen and solder mask. Still would be cheaper than getting one from a breaker. They live in fantasy land.
How did you clean your motors? Any carbon in the armature will cause an overload.
 
I did a redesign of the servo board using surface mount parts, it could easily be 1/3rd the size. The limiting factor is the aluminum L bracket that serves as a heat sink and mount and the ribbon cables would have to be a little longer, all the same connectors. If one of mine takes a dump I will probably do it. The biggest expense is the board. I think 5" x 4.25" is the smallest practical size due to the connectors and fuses which take up a lot of room. $287 for four boards with silkscreen and solder mask. Still would be cheaper than getting one from a breaker. They live in fantasy land.
How did you clean your motors? Any carbon in the armature will cause an overload.

I'm in! I don't care if its 2x the size - We have talked of this. If it includes a parts list if you please. I really just want spares at the ready.
PM me and I arrange payment.

Thank every one of you who are so very helpful sharing - I do what I can.
 
I took the motors apart and cleaned out the armature with isopropyl alcohol. The Z was particularly filthy ...I presume with sure to it's location and never being cleaned before, or gravity helping the brush dust find it's way too the windings. It was a chore, but they ended up liking good. The commutators looked pretty good, so I just cleaned them up with scotch Brite and made sure I got the carbon between the copper pads. If I do it again, I'll run them to my dad's. He has a mica cutter for his lathe to undercut the mica on the commutator, but I wanted to do try to get this thing working. I only reinstalled one so far that had the best brushes, and testing the rest on a the bench. I may go turn the commutators and undercut the mica before I reinstall them.
 
Well relays got my x axis going. I still have problems, but no more in relation to the distribution board.

For others with this later servo distribution board, your rainbow ribbon blue to brown wire voltage should be 16vdc higher than your dc bus (mine is 176vdc). Yellow to brown should be about 20vdc. None of the other wires do anything. Earlier machines were ac low voltage in this cable.
 
I did a redesign of the servo board using surface mount parts, it could easily be 1/3rd the size. The limiting factor is the aluminum L bracket that serves as a heat sink and mount and the ribbon cables would have to be a little longer, all the same connectors. If one of mine takes a dump I will probably do it. The biggest expense is the board. I think 5" x 4.25" is the smallest practical size due to the connectors and fuses which take up a lot of room. $287 for four boards with silkscreen and solder mask. Still would be cheaper than getting one from a breaker. They live in fantasy land.
How did you clean your motors? Any carbon in the armature will cause an overload.
In your redesign, did you make a schematic diagram? It would be great for trouble shooting.
 








 
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