Motor Shield Voltage limit?

I have a v1 motor shield that I've been running a 36V stepper with. I had a 9V power supply on the Arduino but the torque was a bit weak at time. I wasn't sure if the LM293 was getting bad or not enough power. There is reference to the motor shield using up to 24V. So I removed the jumper and wired up a 24V supply that I had directly to the motor shield. I powered that up first ..and two capacitors blew! Did I misunderstand something? The arduino seems to have survived.

Schematic / pictures of how you wired it ?

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Haha I love exploding caps. Welcome and share pictures.

Here's some nice before and after pics. But not too illustrative. I connected and disconnected the external power supply between pictures. The stepper in the picture is connected to the M3 M4 terminals.

Previously I had been using the M1 M2 terminals which seemed to work for a while but then it got weak and I figured the M1 quit working based on voltage measurement while running. So I switched to M3 M4 which ran for several months until I got the same result there. Before scrapping it I'd though Id test the theory that it wasn't enough voltage.

Imgur

Check the voltage rating on the remaining capacitors. Some of them are designed for only 10v with caps rated at 16v.

Just rinse the cap paper off under a running tap, with the help of a soft brush.
Then wash the board in warm water with some dish-wash liquid.
Rinse well with clean water, and let it dry for a few days.
You can use a hair drier to speed things up, but still wait a day before using the board.
After replacing the caps, you will find that all is back to normal, but...

This is NOT a stepper motor board.
Only a brushed DC toy motor driver board.

You need stepper motor driver boards for stepper motors.
Which one depends on the type of stepper motor you have (post a link).
Leo..

stoneman30:
I have a v1 motor shield that I've been running a 36V stepper with. I had a 9V power supply on the Arduino but the torque was a bit weak at time. I wasn't sure if the LM293 was getting bad or not enough power. There is reference to the motor shield using up to 24V. So I removed the jumper and wired up a 24V supply that I had directly to the motor shield. I powered that up first ..and two capacitors blew! Did I misunderstand something? The arduino seems to have survived.

The chip is rated to 36V, and the motor supply capacitors ought to be 35V types or higher - is this a
cheap clone board with lower voltage rated capacitors? Or did you connect the 24V backwards?

What is a 36V stepper? Stepper motors are current rated, not voltage.

I must have mixed the chip and motor rating. This says the motor is 24V. But yes this means it should have been drawing less current than a lower V rated motor, right? What are the odds that the LM293s are bad?

MarkT:
The chip is rated to 36V, and the motor supply capacitors ought to be 35V types or higher - is this a
cheap clone board with lower voltage rated capacitors?

Adafruit v1 motor shields (with L293D chips), and the clones, all have AFAIK 16volt supply caps.
Leo..

stoneman30:
https://www.mitsumi.co.jp/latest/Catalog/pdf/motor_m35sp_9_e.pdf

Seems to be a high-impedance motor (400mA or 600mA@24volt).

Most (low-impedance) stepper motors can't be driven by a v1 shield,
but this one can (if you use >=24volt caps).
The L293D chips could get a bit warm though.

The L293D chips are probably fine. It's just that the caps couldn't handle 24volt.
Leo..

Thanks for the encouragement. I did get the caps replaced with 35v and 50V (just what I could find) and the board is working fine now with a 24v supply.

Wawa:
Seems to be a high-impedance motor (400mA or 600mA@24volt).

Most (low-impedance) stepper motors can't be driven by a v1 shield,
but this one can (if you use >=24volt caps).
The L293D chips could get a bit warm though.

The L293D chips are probably fine. It's just that the caps couldn't handle 24volt.
Leo..

The winding resistance for both types is about 13 ohms, so definitely not for 24V L293D use.

These steppers are designed for current control only. The voltage rating is nonsense, but
all motor spec sheets have a field for voltage which people erroneously fill in for steppers.
The only voltage rating for a stepper is the insulation max voltage.

DRV8825 modules would be ideal. And upto whatever voltage the modules can take is
fine, as they control the current.