rakort
Hot Rolled
- Joined
- Apr 27, 2011
- Location
- Central Wisconsin
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So cleaned up a bit my rheostat trying to figure out if it is good to go and came up with the following readings. I don't have much to compare it with, but poking around it seems about right. What say ye?
View attachment 228488
Brian,So cleaned up a bit my rheostat trying to figure out if it is good to go and came up with the following readings. I don't have much to compare it with, but poking around it seems about right. What say ye?
View attachment 228488
MUST be out of circuit. Is not complicated.
Either way, be rich or be willing to dig-in and master what yah need to know for a good grade of DIY effort. 10EE are unusual. Uncommon. That ain't quite the same as Voodoo or similar persuasions of black magic.
660 Ohms is correct for the generator rheostat. The motor rheostat rating depends in the resistance of the spindle motor's field windings. 400 Ohms is a good number for a motor with 115 V field. The data plate for the square-dial spindle motor is even stamped 400 Ohms for 2400 RPMs (yet the matching rheostat was marked 390 Ohms and set to a maximum resistance of 275 Ohms). (And no, I don't know if the motor reaches full speed at that resistance--all I have is the MG set and I've never powered it up.)Definitely out of circuit. Always dig and master what I own....kind of a freak show that way. Obviously why I'm here analyzing this stat. Some where in the Rhetoric I think I heard I should be looking for something 400 ohms not the 600 ish I was seeing. I found out my fluke is puke for measuring resistance so I'm trying to retrain myself to operate my micronta (radio shack) circa 1980 that has been horribly reliable, but a finicky analog instrument.
Definitely out of circuit. Always dig and master what I own....kind of a freak show that way. Obviously why I'm here analyzing this stat. Some where in the Rhetoric I think I heard I should be looking for something 400 ohms not the 600 ish I was seeing. I found out my fluke is puke for measuring resistance so I'm trying to retrain myself to operate my micronta (radio shack) circa 1980 that has been horribly reliable, but a finicky analog instrument.
It is right handy and MUCH safer to have as many as 3 even 4 meters pre-hooked-up before running a hands-safely-out-of-danger test on lots of 10EE's ish things.
This ain't no audio gear nor PeeCee motherboard.
Lethal voltages, rather.
660 Ohms is correct for the generator rheostat. The motor rheostat rating depends in the resistance of the spindle motor's field windings. 400 Ohms is a good number for a motor with 115 V field. The data plate for the square-dial spindle motor is even stamped 400 Ohms for 2400 RPMs (yet the matching rheostat was marked 390 Ohms and set to a maximum resistance of 275 Ohms). (And no, I don't know if the motor reaches full speed at that resistance--all I have is the MG set and I've never powered it up.)
[FONT=&]When you get the rheostats out, you'll find that the motor rheostat has a jumper between the wiper and one of the winding terminals. Disconnect the jumper and read the resistance between the terminals at either end of the winding. Compare that reading to the value marked on the rheostat, if any. If you get a reading between the wiper and terminal E2 that's any higher than the resistance of the entire winding, over the travel of the wiper, then something is wrong with the wiper. Look at both wipers and make sure that there is still some meat left on the brushes and that the metal of the arms can't contact the windings.[/FONT]
I would appreciate photos of the rheostats and of the stop, if you get a chance.
Cal
T I am happy with the test results and think the rheostat is in serviceable shape.
Thanks for the insight and confirmation that I'm on the right (600 ohmish) track with the 'stat. Interesting that the pixs will show that I found an OE marking reading 625 which I assume is resistance rating. I do understand that 'stats should be reading from 0 to something then at the half way mark or so the resistance locks in for the other half of the turn as my table showed. In the end, I am happy with the test results and think the rheostat is in serviceable shape. ...
View attachment 228555
View attachment 228556
One thing that is bothering me about this rig is one wiper has some "rotational" slop (5 degrees ish). Not sure how the whole wiper attaches to the shaft with some piece of ceramic and some sort of keyway.
Any one blow one of these up with pixs?
The only way that there can be a factor of four difference in the rate of change of resistance with rotation is if they used different types of wire in the second part of the winding. (I have no idea why they would go to that trouble.) If you look closely, the diameter and/or appearance of the windings should change where the resistance per turn changes, and you should be able to find the splice in the two different types of wire....
So 'stats are swinging from 1ish to 400 ohms and the other from 1ish to 660 ohms. Both swing to the mid point then hold solid the rest of the rotation. As you pointed out Cal there is a decided lesser ramp rate in the early part of the rotation. that point persists after a 2nd round of measurements.
...
The only way that there can be a factor of four difference in the rate of change of resistance with rotation is if they used different types of wire in the second part of the winding. (I have no idea why they would go to that trouble.) If you look closely, the diameter and/or appearance of the windings should change where the resistance per turn changes, and you should be able to find the splice in the two different types of wire.
If you managed to sort out your Ohm-meter problems, do me a favor and check the resistance across groups of five or ten winding turns, over the half of the winding where the resistance changes, and see if you can find the spot where the wire type changes.
Cal
I hear you on the non linear resistance readings. I'm confident on the readings. I have no less that 3 meters to cross reference and reconcile the readings. As I said though my fluke is puke in this regards so results there were discarded. I will do some tests like you suggest regarding resistance between a few turns, but not tonight....its been a day....
For sure as at you look at my windings you see where there were splices made in the wires during the winding process, but haven't tried to reconcile that with the non linear ramp rate.
Cal,
there are four distinct zones (~ 45 degrees of rotation) in half of the E1-F2 winding (~180 degrees worth) Each zone is separated by a slice in the winding
there are three distinct zones in half of the E2-GF2 winding (~180 degrees worth) Each zone is separated by a slice in the winding
There must be a different wire in each zone as the "ramp" rate is different in each one
Resistance Readings as follows:
View attachment 228804
Graphically:
View attachment 228803
Thanks for that! That's new information and very interesting.Cal,
there are four distinct zones (~ 45 degrees of rotation) in half of the E1-F2 winding (~180 degrees worth) Each zone is separated by a slice in the winding
there are three distinct zones in half of the E2-GF2 winding (~180 degrees worth) Each zone is separated by a slice in the winding
There must be a different wire in each zone as the "ramp" rate is different in each one
Resistance Readings as follows:
View attachment 228804
Graphically:
View attachment 228803
Thanks for that! That's new information and very interesting.
I'm confused by your rotation numbers. Are you using the wiper angle, or what? I'm asking because there isn't a full 180 degrees rotation from the middle, more like 160-170 degrees.
Cal
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