Fixing my back-gear lockout solenoid

[Mr_CNC_guy]

The back-gear lockout solenoid on my '61 modular 10ee was burned out and had been removed. I have the bad solenoid, and it is clearly burned out. I picked up an apparently good solenoid and was going to install it. However, it does not work. Testing the circuitry, there is 120V AC applied to the coil to pull it in. That is controlled by the AP (anti-plug) relay. The solenoid has no copper shorting ring that I can see. That seems to say that it is a DC solenoid.

A solenoid that is going to run on AC must have a copper shorting ring that acts to maintain the magnetic field during the AC sine wave. Otherwise, they will buzz loudly. Relays with an AC coil have a copper shorting ring.

The solenoid measures 2K ohms, so it is not open circuited. I tried using a full wave diode bridge rectifier to drive the solenoid, and it pulled in OK.

This is a mystery! The schematic that I have shows no rectifier for this solenoid. Actually, the schematic glued to the door shows no back-gear solenoid at all, but the lathe did have a lockout solenoid. The schematic that I have that does show the solenoid, but there is no rectifier. I can make this work by adding a rectifier, but I would like to know how it worked originally.

 

[daryl bane]

I am so ignorant electronically, but it looks like this solenoid is indeed DC. According to my schematics, the backgear solenoid is powered off of wires C7 and F1 coming off of the DC panel. I hope this in anyway helps.

 

[Mr_CNC_guy]

The circuit is a little confusing to me too. It is connected in parallel to the shunt field winding in the schematic that I have. If I measure the voltage with the lathe in forward, but the speed set to zero, I get 54 volts DC with my meter set to DC. If I set the meter to AC, I get 120 volts AC. So there is both a DC and AC component.

Connecting the solenoid directly will not pull it in. If I put a full wave rectifier between the circuit and the solenoid, it pulls in when it should. Clearly there is something funny about this, the schematic does not show any rectifier.

I bought the solenoid with the cast iron mount which contains the locking pin. It looked identical to my original, but it was subtly different. The slot for the belt idler pulley was narrower. The solenoid mounting screws were longer. I had to use my original block with the new solenoid. Perhaps it was from a newer lathe that had a solid state drive.

 

[Jdub63]

If I remember correctly, I discussed the same solenoid with the team at Monarch, they reviewed the diagrams for my 57 WIAD machine and told me the relay was controlled using 120volts DC.

 

[Mr_CNC_guy]

I installed my new solenoid with my original casting, and I used a full wave rectifier. I added a 82uF electrolytic capacitor to the DC side of the rectifier. This raised the DC voltage and caused the solenoid to pull in with a better "thump". It seems to work OK now. I have no idea of how the original (burned out) solenoid worked.

 

[Jdub63]

I installed my new solenoid with my original casting, and I used a full wave rectifier. I added a 82uF electrolytic capacitor to the DC side of the rectifier. This raised the DC voltage and caused the solenoid to pull in with a better "thump". It seems to work OK now. I have no idea of how the original (burned out) solenoid worked.

What part number did you use and where did you find one?

 

[Mr_CNC_guy]

I bought it on eBay. It did not have a part number, it just looked like an exact fit. Clearly the casting was exactly the same, it was just machined a little differently. I could have machined the features that were different, so it would have been functionally identical.

This is the listing;

Monarch 10EE Lathe Pulley Block Bracket w/ Untested Electrical Switch Unit | eBay

Find many great new & used options and get the best deals for Monarch 10EE Lathe Pulley Block Bracket w/ Untested Electrical Switch Unit at the best online prices at eBay! Free shipping for many products!

www.ebay.com