Electro-Pneumatic Two Timer Flasher

A replacement relay arrived in the mail today from ebay. This relay was in much better shape and worked out of the box! I wired up the circuit and it appears to be working!

I've got some more learning to do to understand how to use my oscilloscope. In school, I found the nice Agilent/Keysight scopes with physical knobs real easy to use on a DC circuit. But this is an AC signal. And the Fluke Scopemeters don't have knobs. But it does have a battery, and is practical to hold in your hand. It also has wifi, so you can lock it up in a 480Vac cabinet and view the results on your phone.

I ordered the two timing relays seperately from ebay.

The first one I received was in good condition. I hooked up a 120vac cheater cord to it and plugged it in to a GFCI protected kitchen outlet. The relay coil sounded good, and I could hear the click of the time delay contacts engaging.

The second relay appeared used. There were bits of cut off wire sticking out of the terminals which I removed. I connected cheater cord to it, and plugged it in, hopefull that things would go just as smoothly. I was wrong!

The Buzzzzzzz

Clunking relays often buzz and chatter. I'd say it happens to 5-10% of them. Sometimes it an electrical problem, like a race condition or a poor termination. Though often times its a mechanical problem. At work, I'ved developed the fine art of "whacking it with a screw driver" till it behaves. But I could tell that wasn't going to work for this relay. It buzzed no matter what oriention I held it in.  I took of the timer block and removed the contacts. Still no improvement. Welp time to dive deeper.

This is a highly serviceable relay, and the coil is accessible by four screws on the bottom.

I opened it up, and saw lots of rust.

This relay probably had a hard life in an outdoor enclosure that leaked. I saw that the armature was rusty and started cleaning it up with a brass brush. Then a stainless brush. It sounded much better, but still wasn't perfect. 

I moved onto dry lapping with 600 grit. 

Like every rebellious twenty something, I stayed up late lapping armatures.

This got everything nice and clean and it sounded good enough to move forward.

The contacts also needed cleaning to make continuity. After all that, the timer wasn't working :( 

Off to contact the seller on ebay

Hoping the rubber pieces in the pneumatic timer module aren't dry rotted and cracked