Another failed G0704 motor controller
Add me to the list of failed G0704 motor controllers. Was milling today, nothing crazy just some light work with a 1/2" end mill. Then a loud pop the lights go out. When I get the breaker turned back on and start looking at the mill, I find this:
Don't think overheating was an issue. Nothing was warm to the touch, hadn't even been milling for 5 minutes.
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Last edited by SgtSpyder; 03-06-2011 at 09:59 PM. Reason: Added pic
You should be able to get the original Teccor parts or equivalent, those two are the SCR section of the bridge, it would pay to test or just replace the rectifier pair as well.
It pays on those small SCR bridge drives to bolt a good piece of aluminum to the the rear, in fact Baldor and KB, who make the equivalent drive recommend it.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Is it attached to a steel plate?? If so I'm thinking that could be part of the problem. It doesn't move heat fast enough to be an effective heat sink. You really need to kept those SCR's and Diodes cool. I think the first thing people should do is make a new heatsink for their G0704 Controllers. Then use some good thermal grease like MX-2. I wouldn't use Artic Silver as it requires replacement every year or so. The MX-2 is good for life. I've had it on a very overclocked P4C for over 6 years now and it still preforms just as good as when I installed it. It's also on my Q6600, but it's under water so it's a little harder to judge.
You might be able to get away with just replacing the SCR's but it's a good chance something else blew when they gave out. Doesn't hurt to try though.
I have the Q9650 OCed to 3.2Ghz from a stock 2.8 with arctic silver and water cooled. I haven't had to change out the paste and it has been running strong for 2 years now. I also lapped my water block and processor.
But under water AS5 doesn't get all that hot as it does air cooled. I didn't have problems before with AS5, but I did replace it once after 2 years and my temps dropped 10C. My Q6600 is @ 3.6 for the last 4 years. I have the fets, NB, SB, and CPU under water with EK blocks.
One of my next builds I plan to make my own blocks for the MB instead of paying high dollor for someone elses. I'm really thinking of making an AMD X6 shooting for 4.5ghz with dual 6850s and 6 monitors mounted to the wall. Would be a killer setup. Would spend more on the monitors than the whole rig.
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Jeremiah
PM45 CNC Build in Progress
Apart from heat, it can be caused by a spike, or something that causes one SCR to fire prematurely, or one not turning off when it should.Originally Posted by SgtSpyder
They must fire alternately, so if they happen to both fire at the same time for some reason, it is a dead short across the supply.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
The attached metal isn’t steel; it’s just an ugly piece of cast aluminum. I’m not that familiar with the SCR operation, but the two that had blown are different numbers then the other three.
Looked over the motor to see if it was the cause. Brushes and commutator looked good and from what I could see without pulling the end off the windings looked intact.
Trying to decide a path to mix this problem. The mill is still under warranty with Grizzly, but from what I’ve read in here the replacement controllers that Grizzly is sending out have had a few issues. KB offers a controller that’s the same and it’s not too costly. I also like some of the PWM controllers KB has but there are larger so I’d need to make a larger controller box and the PWM controllers cost a little more.
Too bad that Sangmutan Brushless motor / controller turned out to be a poor performer. This would be a good time to upgrade.
The two blown are SCR's the other three are straight diode rectifiers, in spite of having three leads, two leads are common.
Two diodes form the other half of the bridge and the third is a reverse emf diode across the bridge.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
After my motor blew, I replaced my speed controller with a KBMM-125. They don't cost that much and the difference in quality is apparent. I also replaced the back of the control box with a KB heat sink and mounted it to that. The nice thing about the KBMM is that it has both AC and DC line fuses built in and you can easily swap out the HP resistor so if you swap motors back and forth (like I have been doing) it is easy enough to adjust for it.
Regardless of what route you go, be sure to hold Grizzly accountable. They should send you a replacement. Grizzly needs to know and cover every issue so that they will address the root cause and hopefully prevent other buyers from experiencing the same failure.
Keep us updated on the progress.
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Agreed - and they will make it right. I now have the factory controller and motor as spares.
I'd look at getting the equiv KB controller and have grizzly replace this one and keep it as a spare. My KB board in the PM-25 quit, less dramatically, but still not working so they are not fool-proof either. I think it's a KB board at least. It had a model number on the board that lead me to the KB site.
CNC: Making incorrect parts and breaking stuff, faster and with greater precision.
Also Baldor offer the identical units, just relabled.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
I believe Hoss once said that the controller was a knockoff of the KBC-125 which is basically the same as the KBMM-125. The KBMM just has integrated fuse holders and i believe allows you to set decel time in addition to accel time.
Hy,
this really looks like a 1:1 knock off of a KBLC motor controller. I know because I have one sitting on my shelf. The blown SCRs are no problem at all, solder in equivalent parts wth a little more headroom for overvoltage. The ones blown are good for 400V/10A and voltage spikes may kill them.
Tecor S8025 will do, digikey sells them.. As someone else already said, the other three legged components are D6025l, fast diodes with three legs.
There´s not much the SCRs can take down with them, the power circuit is isolated form the rest of the circuit by the small transformer that can be seen on the left side in the picture.
In case you don´t want to mess with it, send it to John Gerling, he repairs DC drives at good prices and is really fair and honest.
What else? Get some heatsink compound, as it seems the parts are mounted dry on the heatsink. Check your secondary connections, in case you have a short circuit or a loose cable between controller and motor this may cause problems. Check if one of the brushes is stuck, too.
Cheers,
Johann
I called Grizzly today, gave them the story. Seem to be some confusion on which control board it was in his manual. He wasn’t sure it was the motor controller; I told him I was positive it’s the motor controller. Anyway, it had to be forwarded to the electrical guy that should call me tomorrow.
Thanks for the advice on repairing the controller. If it looks like Grizzly is going to take a while with the replacement, I may give swapping the SCRs a try. Right now I’m thinking I need to just get the mill running so I can make mounts for something better. Figured a while back that I would wait till stock setup crapped out before going to something bigger. I’d like to get a 1.5 HP motor to help push the face mill along without getting too warm after only a few passes.
Talked to the Grizzly electrical guy today. He said the controllers are backordered till May, which isn’t good. He also asked me to test the motor with a 12v car battery charger, just to make sure the motor wasn’t the cause. So I gave it a try this evening, the motor turns but seems to vibrate a lot like it was greatly out of balance. I guess this from the really low voltage or maybe the charger sends out a pulse of some kind.
I just fried my second motor 30 minutes ago but the motor controller board looks fine this time.
Grizzly sent me a replacement motor and board last time but it took 3 weeks to get there... ridiculous.
I'm going to try and demand that they upgrade me to another motor as I don't think I should be responsible for swapping these out every other month or paying for an upgraded motor from an outside source and doing the work required to fit it on the machine. Not to mention that my warranty will be up in a few months and I'm not very confident the stock replacement will last long.
Tech support is already closed for the day... will call tomorrow.
-Dave
I'm waiting on my second motor and controller myself. I got an email Feb 21 that they were on backorder, but it did not say when they would arrive. I will say that so far they have been very good about replacing any parts that have failed without any hesitation.
I was told today that Grizzly is working on addressing the issue and will be upgrading/replacing the motor type soon. In the meantime, I had to just order another stock replacement and am unaware on when that is available to ship until they send me an e-mail confirmation.
-Dave
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