MaNo,
  Thanks so much for the advice!  I was really hoping to find someone with the same issue possibly.  It sounds like we have the exact same issue.  You mention yours is mostly Z, and so is mine.  Did you try using A axis to control Z instead of Z?  Did that show the same issues?  Did your issue show up right away or only after the box warmed up?  Also, that's very concerning that you saw X and Y issues but just rarely.  Makes me think I could see them too possibly if I use it a lot more. 

   So this buffer you mention sounds like an excellent way to ensure that the signal out of the parallel port is the proper levels.  Are you suggesting that an older PC may also have a better on board parallel port that isn't "low voltage"?  Do you know if getting a PCI parallel port may also do the trick?  I guess for 20 bucks, this buffer you're pointing out seems to be about the same price as a pci parallel port card anyway, and be a good safey precaution overall.  I think I'll give it a go. 

   One question.  Could you look in your driver box and do you see the same "two white, two black" PIC chip situation?  Not sure how many versions of that box they have out there too though I guess.  Mine is very recently purchased (Oct 2012). 

   

Eradicatore,

OK, I re-read your post and it sounds to be exactly the same problem I had.

Here is some background info.

1) I purchased my units (8621 package) through http://www.discountcampus.com/cgi-bin/webc.exe/store/cncSystemsWin.htm and I can highly recommend them. The system came (June 2012) complete with a Dell Optiplex 380 and PCI parallel card. I opted for Windows OS and March 3. Windows is version 7


2) starting Mach3, the very first moves in any direction were mostly correct. Subsequent moves were incorrect. When the controller was warmed-up, the errors were immediate...always Z- and X+ as Y+  I thought it was me because my lack of knowledge of Mach3. (My other machine has a Syntec controller)

3) Between David (of dPP engineering/discount campus) we spent easily 12 (maybe more) hours over several days on the phone. I have a VOM and we went over all the connections on the board. No problem there. We also checked and tried all possible configurations settings but the problem persisted.

4) I contacted Luiz Ally (TechAlly on youtube) and he graciously send me his XML file. Still, the same problem.

5) David then got a RMA and I send the controller back to Sherline for exchange. Replacement arrived and.....same problem.

6) David got a new RMA for the second unit and I got a new board again. Still the same story.

7) Having never heard of a problem like mine, David suspected too weak a parallel signal and suggested the parallel buffer since nothing else seems to work. Obviously Sherline hasn't heard of it either as they didn't suggest trying a buffer before sending a replacement.

The buffer corrected the problem immediately. In retrospect I wish I had ordered his (dPP) "CNC Extended Box"  (without probe) as that has a built-in buffer but at the time I didn't see the need for the other extras and the switches.

As to the white dots on the IC, well, current unit and previous have them.

I had an old PC (7-8 years??) in junk pile storage and the THAT one works without the buffer.

I am neither a technician nor an expert in the CNC field but it looks to me like you have no other option than to get the buffer or see if a friend has an old PC laying around.

Cheers

Thanks again MaNo!  I ordered the $20 buffer and my sherline box is on it's way back too.  I hope by the end of this week I can confirm your analysis and put this to bed.  I will be so happy when I can finally get to trusting my cut and making some real stuff.  I'm totally new to CNC, so I'm having fun learning along with all this debugging.

So just out of curiousity, did all 4 of your chips have the white dot on them?  Or just the X and Y PIC chips?

Cheers
Justin

Justin, please post results when you get the controller up and running with the buffer. I do believe it will work for you....I know how frustrating it can be to have new new machine sitting there and not being able to use it.

The  the chips with dots are the same 2 as on your image.

Good luck
Norbert

Doh!  I got the buffer and driver box back today, went to hook it up, and realized I need two gender benders!    I should have checked when I ordered it.  Now I have to wait another day to test.  the suspense is killing me! 

.....so,what's happening?

Ok, finally got 2 db25 gender benders from amazon prime.  You wouldn't believe how hard it is (around me anyway) to find a store that sells db25 gender benders!!  Its now all hooked up and working perfectly.  I do however need to test it for a few hours I think to make sure it doesn't fail again once it gets warm.  fingers crossed.  So far so good.

Excellent!!!!  I'm doing a cut now that never worked and now it works perfect.  Thanks MaNo for the 20 dollar patch to my problem!!!  

Sherline was nice about trying to look into it, but they now I think need to make sure to warn all future customers of this potentially very dangerous issue.  Especially since it sounds like the newer  your computer is the more likely it will fail with their CNC driver box alone.

I owe you a pint MaNo! Cheers!

Hi Justin, glad to hear it's working for you. Still, keep observing machine doing some additional projects before you can feel confident enough that the toolpath works out as planned.

Cheers
Norbert

Yup, I totally agree.  I ran about a 30 minute cut and observed the whole time to make sure nothing funny happened.  I will update maybe in a week or two if there are any issues ever again.  Thanks again!

Justin