Trouble with my hobbycnc pro 4 axis board

[twowalls]

I don't really know what is wrong. I bought my controller board about a month ago or so, put it together and testit out. At the time I didn't have a power supply so I just used a 12V battery that I happened to have. I hooked two of my motors up and ran Mach's roadrunner gcode and everything worked great! About a week ago I finished my power supply and hooked one of the motors up and did the same test and again it all worked great. The other day I finished connecting the motors up with some cable and connected them to the power supply. I actually hooked up all three motors (2 EAD's and 1 keling). I've been looking around the forum and realized that I had the keling motor wired up wrong but at the time I didn't know it all I knew was that it didn't work so I tried it on all of the axes. Now none of them work and the LM31 (U5) on the board gets really hot. I check for 5V at the test point and the voltage slowly drops. Is this beyond repair? Does anyone know what is wrong? I tried to sign up for the Hobbycnc yahoo group but was denied. I thought that the criteria for the group was to have purchased a board from them? Anyway I hope that this post is coherent. I have been a long time "looker" but this is my first time posting. I thoroughly enjoy this forum. Thanks.

[pminmo]

disconnect everything but power, does the 5V stay at 5V?

[twowalls]

I have nothing connected except power and the voltage on the 5v test point slowly drops as it did before.

[pminmo]

You could have a bad Vregulator chip, you could have a bad component on the board. If you socketed the IC's pull them and watch 5V. If that changes one of the IC's is bad. If it doesn't then it becomes more of a problem to isolate, but probably the next easy step is to replace the regulator.

[vulcom1]

I would change U5 and also U7 and if your fan is not working change U6. I had the same problem last fall and I would not be suprised if some of your drivers are also shot. My problem was unhooking the steppers while there was still some current in the big cap. I thought it was down but it wasn't and cost me.
If you purchased the board from Hobbycnc then I would email Dave direct and ask him why you where denied.
John

[twowalls]

Well I replaced the regulators U5 and U6 and still not any better. Would it be the two 16 pin IC's? I think that I read somewhere that it is pretty easy to blow those. I emailed Hobbycnc's "contact" email and have not had a reply yet. Hopefully I can get this all ironed out soon. I'm hoping to make the first cut on my machine in a couple of weeks. Thanks.
Nate

[twowalls]

Oops...I meant that I replaced U5 and U7. I had a good 24V on the 24V fan terminal. Thanks.

[pminmo]

Check to make sure you put the electrolytic capacitors in the correct polarity. If one was in backwards that might give you the same symptoms. If one is in backwards, it may feel warm when power is applied for a few seconds.

Did you socket the 14 pin ic's? If so pull them and see if it helps.

[twowalls]

I didn't socket the two chips but I pulled them and again at the 5v test pad when powered I measure 5v then it starts falling...darn.

[pminmo]

Did you check the capacitors?

[vulcom1]

Phil is right about checking the caps as I now remember splitting the case on (C14) and changed C12 and C13 just in case they where weak from the extra voltage. If you don't know how to check them then the easiest way would be to remove them and then check your voltage to see if you still have the drop. If there is no drop then throw them over your sholder and get 3 new ones.
John

[twowalls]

Well, I checked all of my caps and still no luck. I was finally granted access to the yahoo group and I was told to remove my driver chips. So I did that and lo and behold...IT WORKS! Now I just need to replace my driver chips. Thank you all for the help!