Shopsmith Forums

wa2crk wrote:JPG
I would lean that way too. But the surging suggests that the failure may be an error in the system reading the output from the sensor. Possibly very light contact between the position disc and the sensor cable. But that could be a WAG. A wag is a military term meaning a Wild A-- Guess. But I think you already know that!!!
Bill V

I am also acquainted with SWAG as well as SNAFU etc..

What I think I see in the Teknatrol pix is three led - photosensor paired 'gizmos' that likely detect a hole as it passes in a slot between the led and photosensor. The triple set would allow both speed and direction detection. There may be more than one hole/sequence being detected.

I would attribute the surging to a possible rapid make-break developing prior to the ultimate break.

4 sec is a very short time. The software might be hunting.

Realize the software is shutting it down as a result of input to it.

I’ve seen folks do some pretty large turnings on a Power Pro, and have attached a couple of links to videos of a fellow who takes it to a new level, far beyond where I would go with one.

It illustrates the power of the DVR Motor taken to load limits well beyond what I suspect 99.9% of us ever would.

Once you get yours diagnosed, I don’t think the power and duty cycle will be a problem again for you as evidenced in the videos.

https://www.youtube.com/watch?v=rQbzEz0-7X0

https://www.youtube.com/watch?v=dewl3w7X9kc

Everett

JPG
Did you also notice that the three sensors are positioned in an arc on the PC board? Suggests to me that the position disc must have some sort of a lip that passes between the sensors for direction as well as position sensing.
Your statement "I would attribute the surging to a possible rapid make-break developing prior to the ultimate break." is what I was trying to allude to in one of my prior posts. Any rub between the sensor cable and the sensor disc (rapid make and break) I think would cause the surging mentioned. The warning from Teknatool about positioning of that cable is a BIG red flag to me. JMHO.
Bill V

I already removed the rotor to check for dust as part of the initial diagnosis. The rotor is held on by a snap ring and a set screw, and kept locked angularly with the motor's rotor with a key. Yes, there is a ring (or lip) on the bottom of the rotor that has gaps, which create the edge detected by the sensors as the gap goes by.

I saw no wear on the sensors indicating any interference. IIRC, the connector for the sensor cable is actually under the sensor board on the PowerPro motor sensor board, so there really isn't an opportunity for an interference there, either.

Hunting was one of my thought, but I'd expect the speed to oscillate both above and below the set point, not just below.

I'm busy at work so I wasn't able to call Shopsmith during their business hours to get a hold of one of the engineers today. Hopefully tomorrow over lunch I'll get a chance to.

Wow! Most of the stress onm the motor would have been accelerating the log rather than maintaing speed during lathe cutting, but those headstock bearings must have been screaming for mercy!

everettdavis wrote:I’ve seen folks do some pretty large turnings on a Power Pro, and have attached a couple of links to videos of a fellow who takes it to a new level, far beyond where I would go with one.

It illustrates the power of the DVR Motor taken to load limits well beyond what I suspect 99.9% of us ever would.

Once you get yours diagnosed, I don’t think the power and duty cycle will be a problem again for you as evidenced in the videos.

https://www.youtube.com/watch?v=rQbzEz0-7X0

https://www.youtube.com/watch?v=dewl3w7X9kc

Everett

I bet they were! I wonder how much run out existed before and afterward.

Everett

I spoke with Wes yesterday, who was helpful. It sounds like he took a look at the schematics, and based on the symptoms I described, the problem must reside in the power regulator section of the low voltage side of the power supply. He's shipping out a replacement power supply/motor controller unit and wants the original back for analysis.

As a separate project, some time this summer I'm going to mill out a new mounting system for the power supply brick from aluminum, and use heat transfer pads where the mount contacts the supply and the case. The idea is to use the aluminum headstock case as a heatsink, instead of the heatsink to air heat transfer of the current design, which suffers from lack of airflow, and can't transfer much heat to the case because the spring steel mounts have tiny cross-sectional surface area and not so great thermal conductivity due to their being steel. Maybe it's overkill, but I like tinkering and problem solving.

I am glad you are making progress, good to hear.

I would hold off "modifing" anything until you get some experience with the new parts. Yes, there are reports of over heating, but it is not that much of a problem, and doesn't happen very often.

Just some food for thought.

JMHO

rjent wrote:Yes, there are reports of over heating, but it is not that much of a problem, and doesn't happen very often.

Huge problem for me. I haven't even looked at the machine in almost a week cuz I'm just disheartened.

Shug wrote:I spoke with Wes yesterday, who was helpful. It sounds like he took a look at the schematics, and based on the symptoms I described, the problem must reside in the power regulator section of the low voltage side of the power supply. He's shipping out a replacement power supply/motor controller unit and wants the original back for analysis...

Glad you got a chance to talk with Wes! Will be interested to see if this new part solves you problem.