Kearsarge foot pedal grounding question....

Patrick Robert James · Feb 3, 2018

I recently picked up a Kearsarge 402 timer which is great but I don't have a foot switch for it. I do have an old Omega foot switch that is two pronged and is spaced right for the Kearsarge plug, although I will have to trim it. The question I have is if I need to worry about the third prong which appears to be a ground on the Kearsarge.

Here is the outer side of the plug. I'll only be using the bottom two inserts and the top is the ground.

Here is the backside of the plug. The green wire on the left appears to be the ground since it goes straight into the actual cord to the wall. The two green wires on the right in the shadow are the grounds from the outlets for the safelight and the enlarger. Looks like they all go through/around this foot pedal plug.

Here is the plug on the foot switch. Two prongs, no ground.

So my question is do I need to be worried about the ground? Or can I just adapt this foot switch to the timer and go?

After I took these pictures I pulled apart the plug to check if one prong had a ground on it, but they are standard black/white wires. One prong is larger than the other, the larger one being black.

Any suggestions/advice?

Thanks for your help!

AgX · Feb 3, 2018

In case your pedal has an isolating casing and best is even splash-water tight you will not need an earthing.

Instead of showing the timer you should show us the pedal.

ic-racer · Feb 3, 2018

What are the red and orange wires? Do you want to connect them? This may release the magic smoke from inside the device and it will no longer function.

Patrick Robert James · Feb 3, 2018

Magic smoke? Ha.

Here are where the red and orange wires go. The ones on the right are from the pedal outlet (you can clearly see "foot switch" on the circuit board) and the others go to the speaker, so they don't matter here.....

The pedal is just a standard pedal. Not waterproofed or anything.... It is an Omega foot pedal for an Omega timer, or at least I think it is....

AgX · Feb 3, 2018

There is a reason Kearsarge installed an earthed connector, at least with the original pedal in mind.

AgX · Feb 3, 2018

Install a 30mA residual-current-switch in your lab and we can end further discussion. (Unless you move your pedal to another darkroom...)

mshchem · Feb 4, 2018

Don't ruin a nice timer. If you electrocute yourself, well,that's one thing, just don't fry the nice timer

jim10219 · Feb 4, 2018

if It were mine, I wouldn’t worry about it. The chances of something going wrong in a foot switch that would cause it to shock you aren’t good. Plus, I wear rubber soles shoes and have never had an issue with water pooling up in my darkroom floor. Furthermore, all of my outlets are GFI protected.

That being said, it’s always a good idea to ground the chassis of high voltage electronics. And it would be easy to do. You just secure the grounded wire to the chassis of the foot switch on a screw with a star washer to hold it in place. Also make sure the paint is removed from the spot of the connection. The hardest part would be finding a plug the correct plug.

Hilo · Feb 4, 2018

I have two Kearsarge 301 timers (I believe since the mid eighties) and indeed they're great. One of my foot switches came without a cord & plug. I installed that myself and since I could not find this three prong plug I forgot about the earth.
These foot switches in my case are "hand" switches as I place them on the table next to the base board of the enlarger. For me that works much better than placing them on the floor.

AgX · Feb 4, 2018

jim10219 said:
The hardest part would be finding a plug the correct plug.

One can always substitute the connector for a more available model, or even use a fixed cable.

ic-racer · Feb 4, 2018

Sometimes the 'ground' is there for a reason other than 'ground.' For example the unit for this foot switch has pin #3 grounded. Without the ground the switch does not work. Fitting a different foot controller to this unit that connects the other wires together does not do anything (other than release smoke when the pedal is pressed...).

Patrick Robert James · Feb 4, 2018

I appreciate all the responses so far!

Here is a picture of the backside of the connection on the circuit board if this sheds any light on anything. Orange is on the left and yellow is on the right at the F5 location.

jim10219 · Feb 4, 2018

Pictures of the circuit board won’t likely be of any use. A schematic or pictures of the inside of the original pedal might help. As IC Racer pointed out, sometimes the ground is necessary for operation. Though, usually when it it, they don’t route it directly to the chassis like in the picture. However, there are two other wires grounded there as well, which is odd. It could be a part of a Star ground setup, which is uncommon for something like a timer that doesn’t require an ultra low noise circuit to function properly. It’s far more common in hifi audio equipment and such, where people want to remove every tiny bit of static from the signal. Or, it could have been designed by someone who knew electronics, but didn’t know common practices, so they just did it in a nonstandard way.

If you can find a schematic or pics of the inside of the original footswitch, we’ll know for sure. We need a reference point to know what the switch is supposed to do to find out what works and what doesn’t.

jim10219 · Feb 4, 2018

Actually, I have a Zone IV Lektrlab footswitch (without the timer). It appears to use the same connection. I don’t know if it’s compatible with the Kearsarge, and I don’t think it even works (my multimeter doesn’t show the switch doing anything) but at the very least, the plug and cable might be worth repurposing. I have no use for it myself. PM me if you want it and I’ll send it your way for the cost of shipping.

Patrick Robert James · Feb 4, 2018

Thanks Jim! Lots of good info there. And thanks for the offer. I'll pm you....

Kearsarge foot pedal grounding question....

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