Shopsmith Forums

Hello All,
My Power Pro 1, which I love started shutting off all by itself after I left it set in an environmentally controlled shop for 3 months while I toured Europe. I get a strange low voltage warning, but my voltage is fine when I used a voltmeter to check it. I posted this a couple years ago and really never got any ideas back as how to fix it. I have cleaned it out and did get allot of dust out and that seemed to help it, but it still does it from time to time. Does anyone have any ideas? It seems like the contacts on the control panel are voluntaryily shutting down without me touching the controls.
Best,
Don

Don,

Did you see my post before on this issue? The document I posted has some possible explanations for this error and solutions. Unfortunately, Shopsmith no longer repairs or replaces the Gen 1 so you may have to upgrade to the Gen 2 unless you can repair the power supply yourself. See link below:

viewtopic.php?p=271294#p271294

On a normal shutdown of a PP1 it takes roughly 10 or 12 seconds from the time I turn power off until the time that the display goes blank. Nothing happens for the first two seconds or so, then Low Voltage is displayed for the last 8+ seconds. From this, I would conclude that the PP is not directly monitoring line voltage. The behavior is of a slow capacitive discharge of a DC voltage with a DC threshold for triggering Low Voltage. Or at least that's my guess based on never having seen the schematic.

The problem with actually checking line voltage is that it would be most meaningful measuring at the Power Supply input and under load. Because that is essentially what the detector is doing. Conductors, including your shop wiring, the SS power cord, the internal headstock wiring, even the switch, exhibit a normal (but potentially abnormal) voltage drop that increases with current. If you are using an extension cord, it will have a voltage drop that will be worse the longer the cord is and the smaller the conductors are.

The intermittency makes this difficult. Is there any correlation that you can observe between the Low Voltage warning and how hard the machine is working? Higher speeds and heavier cutting would generally correlate with higher current on the input power, and therefore the possibility of excessive line voltage drop. But in my mind this is the least likely of the three possible causes RFGuy provided.

- David

I don't know if this is at all helpful, but on PP1 there are some parameters you can monitor while the machine is running. I use this 'hidden gauge' feature sometimes to monitor the heatsink temperature (in degrees Celsius) when I'm using the machine enough to be concerned about internal temperature. There are a couple of Voltage parameters as well, but I don't know the PowerPro internal design well enough to know what exactly they represent. I do know what is normal, limited to a sample of one.

CAUTION: Monitoring gauges while actively cutting is a bit like texting while driving, a distraction that is not recommended. A second set of eyes of a video recorder that will let you review the readings after the cut is a safer choice.

While the machine is running at the desired speed, simultaneously press LOCK and 9500 to display a parameter in addition to measured RPM. You can then toggle through six parameters using the RPM Up and Down keys. The explanation in parentheses is my opinion or best guess as to what they mean.)

1) T htsnk = xx C (xx is the heatsink temperature in Celsius.)
2) Err = xx rpm (Evidently the difference between commanded and actual speed.)
3) LIREF = xx % (This looks important, but I don't know what it is.)
4) CurLim = xx % (Current Limit, maybe? Mine says 100% and unlike all other parameters I don't see real time changes.)
5) Vd = xxx V (Some intermediate PS voltage? Mine varies over a narrow range from 358 to 360 V.)
6) V Err = xx V (Another voltage? Mine varies over the range of 58 - 60 V.)

- David

David,

My best guess based on the time I spent working on power management (switched mode power supplies), is that "LIREF" is the inductor IREF (reference current) from the power supply (most likely an asymmetric bridge converter since the PowerPro is a switched reluctance type motor design). "Vd" is likely the drain voltage of the power FET's in it. I hope this helps.

It would be nice if Shopsmith made public what the design target is for these parameters, i.e. what is the expected range for each of them. With this, PowerPro owners would have more information for troubleshooting. I mean when you own a car, you can scan and check items through the OBD-II interface. Similarly you should be able to have access to basic information on the PowerPro design, not for reverse engineering, but for basic debug and troubleshooting. JMO.

RFGuy wrote: Mon Jul 06, 2026 10:59 am My best guess based on the time I spent working on power management (switched mode power supplies), is that "LIREF" is the inductor IREF (reference current) from the power supply (most likely an asymmetric bridge converter since the PowerPro is a switched reluctance type motor design). "Vd" is likely the drain voltage of the power FET's in it. I hope this helps.

That seems useful to me, most of my power experience precedes the time when switching power supplies took over the world, at least in my line of work. I started to include what L and I commonly refer to, and decided it was too much guessing to be useful. Based on your thinking for LIREF I scanned it at various 'unloaded' speeds. From experience, we know that the mechanical portions of the headstock create a mechanical load that varies with speed. (With apologies for the table formatting.)

SPEED (RPM) LIREF (%)
500 8 - 12
900 10 - 12
1350 11 - 12
2000 12 - 13
3450 15 - 17
6000 22 - 25
9500 46 - 50

Vd and V Err, on the other hand, don't vary much on my machine at all. But I have excellent power in this case with a very short AWG 12 run on a 20 Amp circuit from the Circuit Breaker Panel to the outlet. My largest line loss would take place in the machine's power cord. So I think it is still possible that the OP will find a correlation between one or both of these and the Low Voltage Error he is experiencing. And I believe that checking T htsnk would allow him to reasonably rule out the Probable Cause of "Control Board or Motor are overheated." (As far as I know there is no direct monitor of motor temperature, and I believe the purpose of all wires to/from the motor are known. But the heatsink in question sits directly above the motor so a hot motor will directly contribute to a hot heatsink.)

- David

I saw your post after reading the notice on ShopSmith's site about the Gen 1 PowerPro headstock's power supply obsolesce. I hope you can find a solution through a third party tech.

Many times I wanted to buy one, but I wasn't confident of the long term reliability to cost ratio. I think I will stick with the mechanical headstock.

Good Luck,