Switch wiring on Rong Fu RF30/31 milling machines

[ARC-170]

I thought I would post this here in case anyone else was replacing their switch and came across the same issues I had. I fried the switch on my RF-30/31 and bought a replacement that was labeled differently than the old one. I got help from another member here (@markba633csi ) on connecting it.

I could not find any references to the new switch anywhere, even though it is EXACTLY the same part number and manufacturer.

The post is here (see post 50): https://www.hobby-machinist.com/threads/rong-fu-rf-31-rf31-drum-switch-motor-wiring.90416/page-5

Here is the connections from post 50. Please note that your switch could be totally different. My "adventures" started on post 34, but the whole thread is worth a read.
1 --- U (motor 1)
5 --- V (motor 4)
9 --- 5 (motor 6)
2 --- R (power 220v)
4 --- S (power 220v)
Add jumper wire from 8 to 10

Before you plug it in/fire it up, check across the power plug prongs with the switch in the off position
Should be no continuity- then in both forward and reverse you should see a few ohms resistance (of motor windings)
If you see a dead short nearly 0 ohms there's a wiring error- check wiring.

If this proves useful, please let us all know. Perhaps it could be a sticky thread?

 

[markba633csi]

Be sure not to forget to mention the switch internal diagram (truth table) since that's where the rubber meets the road, so to speak

 

[ARC-170]

Post #47 has the truth table for the switch. If yours matches this one, then the connections above will work.

 

[Deftone]

Mine has this switch. It's wired for 110v.

It worked but would not stay on. I opened it up and the contacts were burnt. Here's how it was wired:

I honestly don't know jack, about wiring but this seemed to make sense to me. The wires on the right side of the pic are power in and the left side go to the motor. Problem is I could not find a replacement that was even close to the original. So I bought this POWERTEC 120/230V Single Phase On/Off Switch with Hardware Kit (71652).....


Will this switch work and what goes where? Thank you!

 

[ARC-170]

Can you get a truth table or a wiring diagram for the new switch?

It looks like it hooks up the same way, but I'd to find out that wasn't the case. Maybe try wiring it to to 12V light bulb and battery so if you hook it up wrong it won't get fried.

Calling @markba633csi

 

[markba633csi]

Looks like the new one has the line and load terminal pairs on the long side of the switch instead of the short side like the old one

 

[Deftone]

Looks like the new one has the line and load terminal pairs on the long side of the switch instead of the short side like the old one

yes sir. Line in and load out (AFAIK). I'll need to connect some leads to lengthen the load side.

I'm concerned about the grounding as the new switch has a plastic mounting plate and the old switch had a metal mounting plate and the ground wires were connected to the screws that held down the mounting plate. But I think (hope) if I connect the ground wires to the head where they were, then run leads to chassis of the new switch, I'll be ok.

Also trying to get in contact with an Electrician friend who might be able to tell me where I can get a better replacement switch and perhaps some assistance.

Can you get a truth table or a wiring diagram for the new switch?

It looks like it hooks up the same way, but I'd to find out that wasn't the case. Maybe try wiring it to to 12V light bulb and battery so if you hook it up wrong it won't get fried.

Calling @markba633csi

I was going to try it with a power strip with a breaker. I'll look for the truth table, nothing cam with the switch.

Appreciate the assistance, Gentlemen.

 

[markba633csi]

To be sure about the switch pinout you would want to ring out the terminals with a ohmmeter for continuity
Most any cheap meter would work for that. You could even use a cordless drill battery and a small 12 volt bulb to make an improvised tester

 

[RJSakowski]

Coincidentally, the power switch on my 40 y.o. RF30 clone failed on Friday. It turned out that the switch contact for the neutral line were burned beyond salvage. The switch on my machine is a 3PST and was wired so that all three lines, load, neutral, and ground were switched. I moved the neutral line to the ground contacts and used the input terminal from the neutral contacts as a tie point for the ground wires. IMO, the ground line shouldn't be switched anyway. hopefully, now good for another forty years.

 

[markba633csi]

It's not kosher to switch the ground
Probably a case of monkey see, monkey do engineering