2-3 amps for one motor, 5-6 amps for two.

Here ya go...$2.08 each. $1.88 each if you buy ten.

This is an NTE 53001 Bridge Rectifier rated at 10 amps. That gives you a little more "headroom" on the current rating.

They are 5/8" square, with 3/4" long leads, and a hole for a #6 screw in the middle. Easy to work with.

Note that to reach anything close to the 10A rating, that rectifier is normally screwed to a chassis for heat dissipation.  If you actually have 10 amps flowing through the bridge, it'll be dissipating around 7 watts, that size of a part package will be hotter than a firecracker.

GRJ, I figured they could mount it to the chassis somewhere with a #6 screw if they want to heat sink it.

Even if it’s not heat-sinked to the chassis, it’s not going to handle anywhere near 10 amps running a single can motor. At only 3 amps (30% of its max current rating) it will be quite cool.

@gunrunnerjohn posted:

..

If you actually have 10 amps flowing through the bridge, it'll be dissipating around 7 watts, that size of a part package will be hotter than a firecracker.

At any given time, two (2) diodes of a 4-diode bridge rectifier are "ON."  Hotter than a firecracker to say the least!   I think you can buy a 10 Watt soldering iron - as in hot enough to melt solder.

@Rich Melvin posted:

...

At only 3 amps (30% of its max current rating) it will be quite cool.

3 Amps running thru 2 diodes (~0.7 Volts each) is just over 4 Watts.  One would have to be pretty thick-skinned to characterize 4 Watts "quite cool."  I've burnt my finger touching a component dissipating a measly 1 Watt.

@stan2004 posted:

At any given time, two (2) diodes of a 4-diode bridge rectifier are "ON."  Hotter than a firecracker to say the least!   I think you can buy a 10 Watt soldering iron - as in hot enough to melt solder.

Right, I guess I should double that, 14 watts!

@Rich Melvin posted:

GRJ, I figured they could mount it to the chassis somewhere with a #6 screw if they want to heat sink it.

Even if it’s not heat-sinked to the chassis, it’s not going to handle anywhere near 10 amps running a single can motor. At only 3 amps (30% of its max current rating) it will be quite cool.

Yep, a can motor probably isn't going to draw more than an amp or two at the most.  That's likely not a problem, I was just addressing the maximum load.

Since the rectifier is going to pull only as many amps as the motors require, is there any downside in having a rectifier that is oversized?

I recall looking at the rectifier in one of the early Williams motors and it appeared to be pretty "light duty".  Of course only an amp or two doesn't take much.  My recollection is that the rectifier wasn't attached to a heat sink., it was just held up by the wiring.  Of course that was a while ago so my recollections may be pretty foggy.

Thanks for your help.

@CArolina Shagger posted:

Since the rectifier is going to pull only as many amps as the motors require, is there any downside in having a rectifier that is oversized?

No.

No downside, just a larger part.  Here's a TSC TS4K40-A 4A bridge that will more than do the job for a can motor, $0.81/ea., First Class shipping is $4.99 for any reasonable quantity.

Thanks all for your replies.  I tell my buddies that have the fancy new locomotives that when the boards fail, I'll get them going again for a couple of bucks.  Sure no features but at least they won't be sitting on a shelf.

I should add that I have installed some ERR stuff and the installation was straight forward.

Thanks again.