What are symptoms of "blown driver"?

[ejsp]

We recently bought a used Shopbot, circa 2001-2002 with Vexta motors A6497-9412KTG. It worked nicely for about 8 hours when the Y axis suddently began to shutter. I first dropped the Y motor to check the rails. The Y axis still moves quite freely. I then switched the snap connectors between the Y axis motor and the A axis motor. The Y axis motor (with the A axis wiring) moves smooth as silk, while the A axis motor (with the Y axis wiring) shutters. So I know it is not the motor. I deleted my shopbot.ini file but that didn't help. I plan to switch all the wiring but the wiring looks good, making me suspect the problem is with the board. Everything is grounded and the control box is on a separate circuit than the shopbot.

I see a lot of talk on the forum about "blown drivers". Can someone tell me what are the possible symptoms of a "blown driver"?

Also, are there any diagnostics which can be done, such as voltage and amperage measurements, which can check out a driver?

We do not have much money so I really cannot afford buying new drivers all the time. I am very careful with this equipment.

Any input would be appreciated.

[scott_smith]

My Bot is about the same age, an 02. I just had the 3rd set of voltage suppressors go out on my X. It cost me about a buck for the replacement parts from Newark. See my post in this thread for more info. http://www.talkshopbot.com/forum/show.cgi?tpc=26&post=20235#POST20235
To test you can cut the top lead of the parts and try a move command. (The version of control board before ours didn’t have them.) I wouldn't run it long that way because they are there to protect the driver chips.
Scott

[ejsp]

Thanks for the information. I read over your thread and will give it a try. One thing I noticed on my board is that there are two rows of IC chips. The 5 chips in the center of the motherboard, those which are closer to the cables running to the machine, are soldered to the motherboard. The 5 chips farther back are in sockets. I swapped my Y and A and there was no change in the chatter of the Y axis. So the problem is either that other IC chip or the surge protector which you talk about.

Is there any way we can do electrical diagnostics on this board? I would hate to keep sending this board back every 8 hours of run time to replace a single IC chip or suppressor which I could easily, and more cheaply, repair at home.

[Brady Watson]

The path of least resistance would be to just upgrade to a 4G board - no more blown drivers. As it is it sounds like you might have to replace 2 drivers, so you're already part way towards the upgrade...plus you'll pick up 2.5X the resolution and about 2X the speed of your current setup & never have to deal with blown drivers again, unless you do something really harsh...

http://www.shopbottools.com/PRT_4g_Upgrade.htm

-B

[ejsp]

Dear Brady:
Thanks for the reply. I am trying to figure out about blown drivers. Why do you believe I have two blown drivers and not just one that will need to be replaced?

[Brady Watson]

Edward,
I must have misread your original post. At any rate, the 4G upgrade is still a no-brainer. You will no longer run the risk of blowing drivers or need to send them back for repair, plus a whole list of other benefits. If you can swing it, you will not regret the upgrade.

-B