Start up problem with m/G machine?

[SRoe]

I recently fired up my 1948 square dial after 1 1/2 years of storage.
I made the mistake of running it in the wrong rotation and of course the spindle would not turn !
once i figured that out, i flipped 2 of the phases (220V 3 phase input) and Vole` it ran...
but, as i started to increase the speed, it suddenly kicked off off then started to pulse on off on off at the 3 contact breaker inside the electrical metal box.
Is anyone familiar with this problem ? If i hold the breaker bar closed with my hand it sounds fine and RPM go up and down normally, but when i let go it kicks off, tries to restart and kicks off again.
hoping there is an easy fix for this??

 

[Cal Haines]

I recently fired up my 1948 square dial after 1 1/2 years of storage.
I made the mistake of running it in the wrong rotation and of course the spindle would not turn !
once i figured that out, i flipped 2 of the phases (220V 3 phase input) and Vole` it ran...
but, as i started to increase the speed, it suddenly kicked off off then started to pulse on off on off at the 3 contact breaker inside the electrical metal box.
Is anyone familiar with this problem ? If i hold the breaker bar closed with my hand it sounds fine and RPM go up and down normally, but when i let go it kicks off, tries to restart and kicks off again.
hoping there is an easy fix for this??

Welcome to the club!

This is a common problem with square-dial MG machines. The 2000 Ohm resistor (B-E) in the upper right corner of the panel is probably bad. The two 1600 Ohms resistors (A-B) should probably be replaced as well:


The 1600 Ohms resistors are not a stock item. Since they are connected in series a 3000 and a 200 Ohm resistor can be used instead.

You can order them from Newark for $7 to $9 each. Here’s what I would order:
L50J2K0E (2000 Ohm, 50W, 5%) Newark #64K5003
L50J3K0E (3000 Ohm, 50W, 5%) Newark #64K5013
L50J200E (200 Ohm, 50W, 5%) Newark #64K5007
I haven’t checked Digikey or Mouser, but they are also options.

Cal

 

[SRoe]

Welcome to the club!

This is a common problem with square-dial MG machines. The 2000 Ohm resistor (B-E) in the upper right corner of the panel is probably bad. The two 1600 Ohms resistors (A-B) should probably be replaced as well:
View attachment 76511

The 1600 Ohms resistors are not a stock item. Since they are connected in seires a 3000 and a 200 Ohm resistor can be used instead.

You can order them from Newark for $7 to $9 each. Here’s what I would order:
L50J2K0E (2000 Ohm, 50W, 5%) Newark #64K5003
L50J3K0E (3000 Ohm, 50W, 5%) Newark #64K5013
L50J200E (200 Ohm, 50W, 5%) Newark #64K5007
I haven’t checked Digikey or Mouser, but they are also options.

Cal

Hi Cal, Thanks, I do love my 10EE. Really appreciate very much your advice and information. What a great resource you are !
i will order those parts and hope it cures the problem, i did see a small chip on the ceramic of the 2000 ohm resister. Thx for the picture, it was very helpful !!
the machine actually ran fine again this morning, which i was happy to see, it did run too long but it didn't kick out while i was testing it....hmmm Maybe the temperature could effect this also?

BTW Does running the machine backwards do any harm? I would think not but wanted to check with you

Steve

 

[Cal Haines]

... i did see a small chip on the ceramic of the 2000 ohm resister. Thx for the picture, it was very helpful !!
the machine actually ran fine again this morning, which i was happy to see, it did run too long but it didn't kick out while i was testing it....hmmm Maybe the temperature could effect this also?

BTW Does running the machine backwards do any harm? I would think not but wanted to check with you

Hi Steve,

Both temperature and humidity can cause a bad resistor to act intermittently. Also if the machine is run at low speed, say below 400 RPM, the AP (anti-plugging) relay will stay closed and a bad resistor won't matter. You can run the machine until the resistor can be replaced by placing a jumper around the 2000 Ohm resistor (terminals B and E). This defeats the AP relay, so be careful to let the spindle stop before changing directions.

Unlike the spindle motor, the brushes on the generator and the exciter aren't set up to allow it to run in either direction. Running the MG backwards can damage the brushes. As long as you don't see arcing on the brushes or dark streaks on the commutator you're OK. You should only see a single tiny spark and the edge of each brush.

Cal

 

[SRoe]

Hi Steve,

Both temperature and humidity can cause a bad resistor to act intermittently. Also if the machine is run at low speed, say below 400 RPM, the AP (anti-plugging) relay will stay closed and a bad resistor won't matter. You can run the machine until the resistor can be replaced by placing a jumper around the 2000 Ohm resistor (terminals B and E). This defeats the AP relay, so be careful to let the spindle stop before changing directions.

Unlike the spindle motor, the brushes on the generator and the exciter aren't set up to allow it to run in either direction. Running the MG backwards can damage the brushes. As long as you don't see arcing on the brushes or dark streaks on the commutator you're OK. You should only see a single tiny spark and the edge of each brush.

Cal

Thanks Cal, i think i'm okay. Appreciate your follow comments
Steve