Spookydad
Plastic
- Joined
- Dec 15, 2011
- Location
- Houston, Texas
I am working on a '62 Round dial that belongs to a friend who is currently working out of state. Pardon me if I don't have all the Monarch lingo down just yet.
It has been working fine for the past year or so. It is on straight 3 phase power so no VFD. When it arrived originally, one of the wires on the largest vacuum tubes was broken off and the tube was replaced. A couple of tubes were purchased on ebay but only the one with the broken wire needed to be replaced. It ran fine.
Recently the replaced tube blew. On inspection it appears the heater coil is blown. The old tube had charred wiring around where the one wire broke off. We replaced the blown tube with the other tube that was purchased on ebay. It didn't glow or get warm. We swapped the positions of the tubes and the tube that was original to the machine (when we got it) works in either position. The replacement doesn't work in either position but the heater coil seems to work and there is comparable resistance on the heater circuits of both tubes.
We have someone who builds tube based Guitar amps that has tested some of the smaller tubes and gone over the various resistors and capacitors on the main panel. Everything seems to check out.
The spindle will start with only one working tube but it is obviously not getting enough power and will trip the breaker after less than a minute. When the machine starts there is a buzzing coming from above the forward/reverse contactors. The actual contacts on the contactors were badly pitted but were cleaned up as best as we could when the machine arrived. There appears to be some arcing going on now. Continuity was tested on all the cloth covered wires on each contactor. If the machine is started in forward, the buzzing seems to be coming from the coil above the contactor on the left, and if it is started in reverse the coil above the contactor on the right appears to be buzzing.
The machine will just barely start on belt drive but will start reasonably with the back gears, although the motor seems to be running faster than normal.
There is oil in all the sight glasses and the oils have all been drained and replaced regularly. We are getting the common leak from the chuck reservoir into the main reservoir. The spindle turns freely and runs as quiet as only a Monarch can. (Well it was until the tube blew.) The machine gets light but regular use and we have a South Bend for medium work, and a 16" Leblond for heavy work.
Would it be possible to put some solder on the surface of the contactor nuts to level out the surface? The pitting is almost 1/8" deep on some with a groove that matches the 1/2 round shape of the floating part of the contactor. I don't think this will solve our problem as the pitting is mostly on the forward contactor and the symptoms are the worst when trying to run it backwards.
What should I check next?
It has been working fine for the past year or so. It is on straight 3 phase power so no VFD. When it arrived originally, one of the wires on the largest vacuum tubes was broken off and the tube was replaced. A couple of tubes were purchased on ebay but only the one with the broken wire needed to be replaced. It ran fine.
Recently the replaced tube blew. On inspection it appears the heater coil is blown. The old tube had charred wiring around where the one wire broke off. We replaced the blown tube with the other tube that was purchased on ebay. It didn't glow or get warm. We swapped the positions of the tubes and the tube that was original to the machine (when we got it) works in either position. The replacement doesn't work in either position but the heater coil seems to work and there is comparable resistance on the heater circuits of both tubes.
We have someone who builds tube based Guitar amps that has tested some of the smaller tubes and gone over the various resistors and capacitors on the main panel. Everything seems to check out.
The spindle will start with only one working tube but it is obviously not getting enough power and will trip the breaker after less than a minute. When the machine starts there is a buzzing coming from above the forward/reverse contactors. The actual contacts on the contactors were badly pitted but were cleaned up as best as we could when the machine arrived. There appears to be some arcing going on now. Continuity was tested on all the cloth covered wires on each contactor. If the machine is started in forward, the buzzing seems to be coming from the coil above the contactor on the left, and if it is started in reverse the coil above the contactor on the right appears to be buzzing.
The machine will just barely start on belt drive but will start reasonably with the back gears, although the motor seems to be running faster than normal.
There is oil in all the sight glasses and the oils have all been drained and replaced regularly. We are getting the common leak from the chuck reservoir into the main reservoir. The spindle turns freely and runs as quiet as only a Monarch can. (Well it was until the tube blew.) The machine gets light but regular use and we have a South Bend for medium work, and a 16" Leblond for heavy work.
Would it be possible to put some solder on the surface of the contactor nuts to level out the surface? The pitting is almost 1/8" deep on some with a groove that matches the 1/2 round shape of the floating part of the contactor. I don't think this will solve our problem as the pitting is mostly on the forward contactor and the symptoms are the worst when trying to run it backwards.
What should I check next?
