3520 possible future problem?

[Bernie Kopfer]

I have a PM 3520B that is 7 years old with only light usage. Never a problem until a few days ago. I hadn’t used the lathe in about 2 months. Mounted a bowl turned the speed dial down and pulled the start knob. Nothing! No noise, dead silence, not even a click. Turned the speed dial, spun by hand, nothing. Obvious that juice was at machine since the speed display was on and worked when I hand spun.
pulled the plug and received a couple of switch-like clicks. Measured the voltage, 121 each leg. Plugged it back in, got a couple of clicks and the lathe has run fine since.
Has anyone had this happen to them? Any idea what happened and most importantly is this a harbinger of problems to come?

[John K Jordan]

I have a PM 3520B that is 7 years old with only light usage. Never a problem until a few days ago. I hadn’t used the lathe in about 2 months. Mounted a bowl turned the speed dial down and pulled the start knob. Nothing! No noise, dead silence, not even a click. Turned the speed dial, spun by hand, nothing. Obvious that juice was at machine since the speed display was on and worked when I hand spun.
pulled the plug and received a couple of switch-like clicks. Measured the voltage, 121 each leg. Plugged it back in, got a couple of clicks and the lathe has run fine since.
Has anyone had this happen to them? Any idea what happened and most importantly is this a harbinger of problems to come?

Did you have an error code on the back of display on the back of the VFD?

Yes I've seen that on PM and Jet lathes with the Delta S1 inverter. Was the power to the lathe off/unplugged when not in use? Mine were plugged in so I figured it was some power transient. I disconnect the power now when not in use, no further problems.

Some years ago this started happening regularly on a Jet 1642 and eventually the inverter quit completely, dead, no lights. I had left that lathe plugged in all the time. All my lathes are on power disconnect switches now. Some turn off the breaker. Won't stop a major electronic's-frying from a lightning strike that can come in on the ground wire but I think it helps against milder transients. Many people have said they unplug the lathe from the receptacle every time they leave the shop.

I've heard of some PM 3520s that failed with degrading capacitors in the VFD, fixed by replacing the caps.

JKJ

[Bernie Kopfer]

Thanks for your reply. One relearns something new everyday. If I knew there was a status display window on the back of the inverter I’d forgotten about it years ago. So in reading your post John the question comes to me why the disconnect when not in use? Is this because of possible lightning strikes nearby or are the VFDs hypersensitive to transient voltage variations? Mine’s been plugged in for 7 years. Is this my punishment? Are you saying that all VFD equipped machines should be unplugged when not in use? This new to me and I’m certainly willing to learn the why and why not.

[Thomas Canfield]

I have had similar problem with the "home addition start/stop" switch not working. Cleaning dust out or replacing the standard switch solved the problem. The indication light do not indicate power to the motor but that there is power to control and then the on/off switch(s) take over from there.

[John K Jordan]

Thanks for your reply. One relearns something new everyday. If I knew there was a status display window on the back of the inverter I’d forgotten about it years ago. So in reading your post John the question comes to me why the disconnect when not in use? Is this because of possible lightning strikes nearby or are the VFDs hypersensitive to transient voltage variations? Mine’s been plugged in for 7 years. Is this my punishment? Are you saying that all VFD equipped machines should be unplugged when not in use? This new to me and I’m certainly willing to learn the why and why not.

I'm no expert. There has been discussion here about voltage transients and how they can damage various types of electronics. A lighting strike even a long distance away can cause significant surges through power lines. I don't consider the VFDs hypersensitive but disconnecting is cheap insurance on something that would cost more than a clock or radio to replace. I don't like to unplug so I disconnect with a switch. The best switch would disconnect all three conductors but even this might not protect from a direct or very close lightning strike since it can jump switch contacts but such strikes are rare.

Some people disconnect all of their machines when not in use. I don't. (I've have also known people who are so afraid of lightning from a bad experience they turn off and unplug everything and sit trembling in the middle of the room until the storm passes.) I don't turn off and disconnect computers and monitors either but I do use good uninterruptible power supplies with transient filters. Like anything, there is a risk vs benefit evaluation. Good homeowners insurance can help with peace of mind.

JKJ

[Randy Heinemann]

I'm no electrician or expert on motors. I asked Powermatic support when I got my 3520c recently and they directed me to unplug the lathe when not in use to avoid damage from power surges. This direction came in response to my question about plugging the lathe into a surge protector rather than directly into the outlet. Apparently the VFD won't run plugged into a surge protector. I've religiously unplugged the lather each time I quit turning unless I'm going right back at it. If you're power is subject to periodic surges it would seem to be an important thing to do. Even if not, surges do occur with or without lightning storms. The replacement for a burnt up unit is about $1200 I've been told.

[Bernie Kopfer]

This is an interesting discussion and needs the participation of the wider SMC community. Surely among the many readers someone has direct experience related to this. No offense intended Randy but the advice you were given almost falls into the category of not driving the car to avoid accidents. I have the lathe and a 4hp BS on the same circuit (don’t ask) so I could with some work install a 220 switch at the outlet box and solve what might be a possible problem. I just read both manuals and neither say a word about unplugging the machines when not in use nor do they mention a problem with power surges. So that is why I would like to hear from the wider community to see if this is a real problem or a theoretical one. Perhaps this thread should be transferred to the Power Machine column.

[Tim Elett]

It would be nice to have a electrician or two share some advice, I googled vfd protection and the article said that protection is available ,so is it possible that the company that supplies the vfd to the manufacturer have protection built in the control board?

[Steve Nix]

I installed a switch on both my lathes, ones 220 the other is 110. I flip the switches when I leave the shop, better safe than sorry. I lost a 440v irritation well and a computer to a power surge once. Nothing was stated in the manual about disconnecting power, it just a habit for me to disconnect anything that a electronic circuit board

[Brice Rogers]

I've got a Grizzly G0766 lathe. The main power button is a 220 volt switch with a relay built in. So, when I plug in the lathe, the 220 volt power stops at the switch. When I press the on button, the relay latches and connects the 220 volts to the controller. So if I get a minor power surge with the lathe off - - say one thousand volts, it is likely that it won't arc across.

But if we are having potentially stormy weather, I just unplug the lathe.

But, with a lightning strike, strange things happen. I have had three very close encounters with lightning. Stuff vaporized. Lots of electronic damage. So, I don't consider the latching on-switch to be immune for super high voltages.

[John Keeton]

“Analysis paralysis is an inability to make a decision due to over-thinking a problem. An individual or a group can have too much data. The result is endless wrangling over the upsides and downsides of each option, and an inability to pick one.”

For the 12 years I have been turning, I habitually unplug my lathe when I leave the shop. I don’t know if it is “required” or even if it is “advisable.” But, it just seems to be a guaranteed preventative measure that has no cost and is 100% effective. I honestly am amused at this debate and have enjoyed seeing it develop. For comedic interest, I suggest including reasons for “not unplugging.” That data will no doubt add considerable interest!

[Dave Mount]

...I asked Powermatic support when I got my 3520c recently and they directed me to unplug the lathe when not in use to avoid damage from power surges. This direction came in response to my question about plugging the lathe into a surge protector rather than directly into the outlet.

Hi, my name is Dave and I'm an unplugger (by intent, if not by execution). . .

I have a 3520B, but I find it kind of interesting that PM wants you to unplug a 3520C considering it has a main power switch on the lathe (separate from and ahead of the red mushroom knob). That, combined with their recommendation to unplug the unit, suggests that that main power switch is not sufficient separation of the electronics from the power grid to prevent potential damage. I also find it amusing that they want you to unplug your 3520C when they don't see fit to ship their lathes with a plug on the end of the cord!! I took the lack of plug to suggest they wanted you to hard wire the unit into a box.

Best,

Dave

[Bernie Kopfer]

“Analysis paralysis is an inability to make a decision due to over-thinking a problem. An individual or a group can have too much data. The result is endless wrangling over the upsides and downsides of each option, and an inability to pick one.”
For the 12 years I have been turning, I habitually unplug my lathe when I leave the shop. I don’t know if it is “required” or even if it is “advisable.” But, it just seems to be a guaranteed preventative measure that has no cost and is 100% effective. I honestly am amused at this debate and have enjoyed seeing it develop. For comedic interest, I suggest including reasons for “not unplugging.” That data will no doubt add considerable interest!

What can we say John,but that you’re easily entertained.😊 Collective wisdom has been shown to be more accurate than experts in the area of estimating numbers or results. But here we are seeking knowledge and understanding not just consensus of opinions or experiences.
Of course un plugging anything with a electronic circuit is the “ safest” action. Lightning strikes do happen and in some areas they are rather common. Routine power surges are also said to be a possible source of potential damage but IMLE I’ve not heard of them destroying VFDs. TVs are full of circuit boards yet there is no recommendation to unplug when not in use and if routine surges are damaging why would it not not happen when the device is in use?

[John K Jordan]

... Lightning strikes do happen and in some areas they are rather common. Routine power surges are also said to be a possible source of potential damage but IMLE I’ve not heard of them destroying VFDs. TVs are full of circuit boards yet there is no recommendation to unplug when not in use and if routine surges are damaging why would it not not happen when the device is in use?

We had a lightning strike in a storm Monday down the hill behind the house. It blew apart a the top of a 38" red oak tree about !50 down the hill and threw chunks of bark over 120' in several directions. Knocked down a 24" diameter limb maybe 40' long!

All utilities are underground except for one 50' run of Comcast cable stapled low to one side of the house. The strike evidently induced a surge in the coaxial cable that feeds our TVs and internet. Everything with electronics is plugged into uninterruptible power supplies throughout the house and shop.

No TVs, cable boxes, or DVRs were affected even when plugged in. The Comcast cable model was damaged although all the diagnostics and indicator lights showed it to be working properly. Simply replacing the cable modem restored our service. The service guy also replaced the grounding blocks in case one had developed enough resistance to fail to divert a surge.

As mentioned, I do switch the lathes off when not in use. All power lines on the property incuding to the shop are also underground but I suppose a direct strike on the lines on the poles about 800' from the shop might create a damaging surge.

JKJ

[Ken Fitzgerald]

In the early '70s while stationed at NAS Meridian, MS I worked air traffic control maintenance. I had to deal with the effects on radar (GCA ground controlled approach)used to land air craft. One day while on duty, the radar on the south runway went down. The crash crew sitting at the hardstand near the radar saw the lightning strike the ground next to the runway 1/4 mile from the radar. The AC power cables for the runway lighting was directly below where the lightning struck. We were a couple weeks repairing all the damage to the radar. At the radar trailers, I saw copper pins as big as my thumb in a large power connector melted. The connector was welded to the jack. It wasn't a direct hit it was 1/4 mile away as estimated by witnesses.

I worked installing and maintaining CT and MR scanners for 34 years until my sudden deafness caused my retirement in 2011. I've seen the intermittent computer problems caused by power transients resetting part of a computer system but not the resetting the whole system. I have dealt with the problems professionally caused by power surges.

I always encouraged my customers to shut their equipment off each evening after scanning their last patient. When you have a system that has more than one processor/computer in it, some of the processors can be more sensitive to transient power surges than others. Thus in a multiprocessor system, one may have to reboot the system to get it to function normally so the easiest way ,to insure normal operation is to shut the system off. Note I didn't tell them to turn off power to the system but shut the system itself off.

In my shop, I unplug my PM-3520B each time I am done turning for the day. When I leave town for a day or longer all of my tools including my wall mounted Oneida Super Gorilla DC are unplugged. It's cheap insurance to prevent damage by intermittent transient power surges.

Another thing to consider when talking about damaging electronics. Damage doesn't always have to be catastrophic resulting in immediate failure but can also accumulative so that over an extended period of time the damage finally results in failure.

[Kyle Iwamoto]

. TVs are full of circuit boards yet there is no recommendation to unplug when not in use and if routine surges are damaging why would it not not happen when the device is in use?

You have to compare apples to apples.
IMO your (my) TV is a shelf life item. In 3 tears, your TV is old and out dated, it will probably break down and need replacement in 5 years. If you were to unplug the TV, you would need to reprogram everything. I had a TV that required servicing and every time I had to reprogram everything. So no, I'm not unplugging my TV. I think brown outs are more common than surges, and I have had both happen to my TV, long time ago. No damage, but the TV obviously didn't like it. Made funny squealing noises when not enough voltage, and the surge protector I assume, saved the TV since it tripped. It does happen. If I recall, both (and only 2) things happened close together. I guess the power company was having some issues.

I open the circuit breaker for my lathe after every use. May not protect from a lightning surge. Maybe I should also unplug it. It takes just a few seconds to do either.
Just my $0.02.

[allen thunem]

You always seem to hit the nail smack dab on the head john
Not to mention you do it with such comic relief



“Analysis paralysis is an inability to make a decision due to over-thinking a problem. An individual or a group can have too much data. The result is endless wrangling over the upsides and downsides of each option, and an inability to pick one.”

For the 12 years I have been turning, I habitually unplug my lathe when I leave the shop. I don’t know if it is “required” or even if it is “advisable.” But, it just seems to be a guaranteed preventative measure that has no cost and is 100% effective. I honestly am amused at this debate and have enjoyed seeing it develop. For comedic interest, I suggest including reasons for “not unplugging.” That data will no doubt add considerable interest!

[Allen Mattsen]

My power went out suddenly today. Twice! It's a heat wave here and 110° currently. I'm glad to have left my Laguna 2436 unplugged and it wasn't affected. While out still now I went and unplugged the rest of my tools. Didn't really expect an outage in June...

[Zachary Hoyt]

I have a VFD on my new old drill press, and I only plug it in when I am going to use it, and then unplug it afterward. It seems cheaper than buying a DPDT switch, and not much harder than flipping a switch if I had one. The plug is right next to my Shopsmith which has a couple of holes in the frame that are for a function I don't use, so it's easy to drop the plug into the hole and then it's only about a foot from the power strip when I want to plug it in. I also put a plastic bag over the VFD when I am not using it, to keep dust out.

[Randy Heinemann]

I'm no electrician and, therefore, I don't know all the issues with power surges, lightning strikes, and power outages.

I do know, however, how much the 3502C just cost me and also know that replacement of the VFD (which I believe is the black box on the backside of the headstock which is connected to the outlet) costs $1,200. I also don't wish to get into a drawn out struggle with Powermatic to get an expensive part replaced under warranty.) I also know that I had to replace my electronic controller on my Nova midi-lathe (which I know isn't the same as the Powermatic VFD). I could never prove nor disprove the cause of this. I also don't know if damage can still occur even if the power switch is turned off but the plug is still in the outlet. I just know there is no reason to take the chance that damage might occur from a storm or other power surge. While there is no reason to unplug every time there is a brief rest before using the lathe again, I do unplug each day when I am done. Just because electronics in your home survived a nearby lightning strike once doesn't mean that it will again. Plus, surges can weaken devices for later failure.

Researching this, I found a variety of answers (as we all do these days on the internet). From that, I could draw no solid conclusion and just decided to unplug when not in use.