Acu-Rite III DRO Troubleshooting

Hi all. Searched the site pretty hard but have been unsuccessful in finding a similar thread on the problem I'm having. Ok, here it goes. Been trying real hard to get my Dad's Mold shop up and running from having the doors shut 14 years ago. So with the help of all the information here on the site I've been able get everything up and running with the exception of one "Y" Axis on the Acu-Rite III DRO on the knee mill. First off, the DRO wouldn't zero out after switching it on. It only showed the Fault mark on all three axis. So after a bit of swapping parts I was able to determine the small capacitor on the power supply board was at fault. Guess the electrolyte lost it fizz. After replacing it from one I found at the local Radio Shack. Things were looking pretty good with the exception of when I connect the round 6 pin "Y" axis connector to the back of the DRO causing none of the axis to work. They all stay at "0" with no change when movement is applied. Basically it locks the readings on all axis. But when I disconnect the "Y" axis cable from the DRO, Z and X axis both work perfectly fine. I've pulled the "Y" axis reading head and cleaned both the glass scale and the reading head. Though I haven't been able to locate the correct "Temporary alignment Bracket" for actually being able to square the head up and final the install. so if anyone out there has one they can borrow me or has measurements they can share I would be more then appreciative. Anyway, I thought I might throw this out there and see if anyone has had this type of issue and was willing to share some insight on what my problem might be.

Also, I've checked continuity from the Reading head board to the pin on the cable. All 5 wires check out fine. One thing I did notice was that the ball spring on the reading head appeared to be rubbing on the circuitry on the board. Does anyone know if this is normal? Is it possible for the ball spring to be shorting out the system and causing this type of problem.

Again, Thank you for all the information that has gotten me this far.
Ri

Have you called Acu-Rite, they might be able to help...

adc1963 said:

Have you called Acu-Rite, they might be able to help...

Click to expand...

Acu-rite will sell him a new one, but offer no help at all with his current one - that I can guarantee... The manuals are available on Acu-rites website, but the OP is already into more complex stuff (swapping out caps) than the manual ever offered, so they are probably of limited use.
It might just be easier to jump over a replacement unit ($150-$200 on ebay) and move on - or use that to aid in the troubleshooting?

OP:
Have you tried swapping all the scale plugs around on the sockets? Does the "failure" always stay with the same socket on the ARiii or does it move with the scale? That will tell you where the problem is. I note there is reference of pull-up resistors and voltage supply to the scales in the ARiii manual that would be easy to verify.
If you plug the Y alone into any/all of the sockets individually (only one plug in any of the three sockets) do they work correctly?

Next, are you running the same scales on all three axis? The dips need to be set accordingly, although from my experience they don't stop them working; they just don't read properly.

Correct - Manuals are not helping at this point. Yes, playing musical chairs with switching the cables from one port axis to the other makes no change to the issue I'm having. Everything works fine until the "Y" axis is connected to the DRO. Then everything freezes. I'm not 100% sure but I have a strong feeling that the ball spring is shorting out the circuitry on the reading head board. I haven't had much time to investigate further since I posted this but will have plenty of time to check things out further this weekend. If I locate the problem I'll certainly post back my findings.

Thanks
RI

Is it the same scale/reader head being plugged into the Y axis? Or is it just the Y axis on the DRO that is being an issue? I have seen this happen a few times, where somehow a few of the lines are shorted together.

Secondly, if you are talking about the little red tabs to align the reader head properly, PM me and I can send you some. I have hundreds of them.

Jon

Judging from what you have already done I assume you know your around a p.c. board. Have you checked where the plugs ares soldered to the p.c. board for broken or shorted traces?

I believe the OP is saying that it doesn't matter if he connects Xscale to Xreadout, Xscale to Yreadout, Xscale to Zreadout, Yscale to Xreadout, Yscale to Yreadout, etc, etc, the problem always rears its head whenever the Y scale is plugged into the readout regardless. So this is unlikely to be a Acu-rriteiii issue, so much as a scale issue.
As this is the Y scale, it can't be that expensive to just source a replacement, even a used one. That said, if the OP could tell us what scale type we are discussing might help (AR5 perhaps)?

Had a day to sit and go through it again and wanted to let everyone know what I found. Wanted to see if that ball spring was shorting out and causing the issue as originally thought. Sure as crap.. it was. Now I need to know why. Ran an indicator along the outside housing. Straight.. Check the glass scale again. Clean, no cracks or chips. Everything seems to be where it should be. Is it possible for the ball spring to lose tension just sitting there? Has anyone ever replaced the ball spring before? Or is it an assembly replacement only? Can the spring be simply bent back or is it specific for alignment? Though just a guess, I believe the scale is fine. Just need to figure out the spring and do the alignment.

Again, thanks all. If I can't get it, I'll check back and see if one of you have a replacement scale. It's a AR 5 (22" long outer housing) .0005 resolution.

Ri