SC-1 Question "electronic"

Hello W&S people,

I have a question I feel only a W&S service
tech guy would know, I have a W&S SC-1 that I
program, repair, run, and own, a wile back I
had the small index motor go bad so I got another
one and installed it, then I tuned the servo
board as per the factory papers, then as per a
recommendion of a repair person I carefully
cleaned the insides of the TWO potientiometers
that has something to do with position of that
big turret. I cleaned some sort of "gunk" out
of it as the repair guy said to do.. but now
when the the turret index's its a bit clunky
and I am sure its a electric problem.. my
question is: was this "gunk" a special grease
that has to be in the pot or was it just 30
years of goo the built up in the Potientiometer?

Any Help in keeping my old 1-SC's running
is greatly appreciated.

Dave.

I can help you with that but need a better description of the movement than "a bit clunky." Is this perchance the machine someone was here with earlier where they replaced the index motor with a treadmill motor? I always avoided taking those pots apart but perhaps you had nothing to lose. They are expensive as hell if you have to buy them and G & L is probably the only source. The course pot selects the correct turret position and the fine pot selects the final position. If they are not set correctly there may be a roughness near position when the control board switches which pot it is looking at. Too little tach voltage will cause the turret to osscilate when it is trying to stop at final position. A substitute motor may not have a suitable tach voltage.
Am I correct to assume this is an old GE 7542 with an index control board on the mag panel door?
Be sure both the unclamp and relief solenoids for the turret located by the X axis motor are operating as expected. If the relief solenoid does not pick the turret may still rotate but is hard to turn and it won't respond correctly.

Tell me what you have.
John

Hi Mike,

No im not the guy who put a tredmill motor
on a machine, "I didnt know that was possible"
what I have is a spair servo motor thats correct
off a junked SC-1. The origional motor got so
weak I swaped it with my spair, and I tuned and
and cleaned the index boards plus cleaned the
index "pots" the curvic coupling seprates
right, and the turret spins to the correct place
like it should, but instead of a smooth position
it pops and jerks a bit wile in rotation. So I
cleaned, added new bearings, and brushes to the
origional index motor and placed it on the 1-sc
now the motor runs well but still the same jerky
rotation just not quite in the same way.. but
i still use the machine... Now just last month
I got another 1-SC and currently getting it up
and running, and i found out it has the same
problem as my old 1-SC.. it would be nice if I
could get both machine's indexing smoothly as
it was a few months back... also both of my
machines have GE 7542 controls... M-5000 machine

PS: the "POTS" have a non contact point in them,
could the grease give it a bit of conduction and
smooth the resistance as it goes from high to
low ???


any help is very much appreciated,

Thanks
Dave.

Hi John,

Sorry about the name mix up in the above
post, its early and im still half asleep...


Thanks
Dave.

Hi Dave,
No error observed, wife calls me Mike.
What usually happens to the pots is that they end up sitting in one of 12 spots on the course pot and the same spot all the time on the fine pot. You could try switching the course and fine pots with each other although that involves repinning the gears on the pot shafts and require another realignment. That would get you new spots on the pots to locate on. When the turret is looking for position it is only looking at the course pot so bad spots on it might make it jerky.
Roughness during rotation could be due to uneven output from the index motor tach. In Houston we used to have a lot of trouble, more so with the axis motor tachs, becoming corroded which caused the output to go down or become uneven. Decreasing tach voltage raises the gain until the axes became unstable and they wouldn't sit still in position affecting the surface finish. We had some little commutator polishing stones that we used to clean tach commutators with but the index tach is different and probably can't be cleaned. A typing eraser is a good substitute for a tach cleaning stone. Just jog the axis slow and polish the comm as it rotates.
Back to the pots, the non-contact point you spoke of must be surface corrosion or burning on the surface of the restive material. I don't know if you can see it or polish it off gently or not. The pot isn't burned out or it wouldn't work at all. When I was selling my time fixing 1-SC's it was more economical for my customers to buy the pot than pay me to mess with one so I haven't dug into them much other than a forensic disassembly to see if I could see what killed one. A lot of times it involved coolant.
Did you check out the solenoids? A relief solenoid not picking will make the turret turn rough.
You can run your index motor on a car or fork truck battery and scope the tach voltage to see if it is smooth and also see if the motor runs smooth. All of the servo motors on a 1-SC are permanent magnet motors that can be damaged if not disassembled correctly despite what you may have read on this forum. Pulling the armature out of the case may weaken the magnets and reduce the available torque. I am not a motor repair specialist but have heard it recommended to slide steel shim stock into the motor around the armature before pulling the armature out. This would be a large piece of shim stock, enough to surround the arm..
Take the top cover off of the turret box and make sure the turret bar is getting oil. There is a spray lube line in there that should be spraying the turret bar. On an old worn machine you may not see oil there while sitting with the spindle stopped because of excess leakage from old headstock clutches which are both energized when stopped. If you run the spindle or go to free spindle in manual mode the oil should come back. If not you have a bigger problem.
Write if you get some more info.
John

Hi John,

Ok ill look and work on it this weekend
and get back to you.

Thanks for the help.

Dave.

Dave,
I also forgot to mention that the problem could be in the servo drive itself. It is a 3 phase drive with 3 SCR's firing in each direction. It will still run with one or maybe even 2 SCR's not firing but may have a 60 cycle hum and will have reduced torque. Usually with 2 out it will trip a circuit breaker which will be the good phase overloaded. Most of the failures will be a 709 or 741 op amp.. Also popular are those 8 caps on the right end of the PC board, 47 or 50 MFD if I remember right.
John

Hi John,

Thanks for the info, I cleaned and rebuilt
the servo motor and now it runs fine! I will
still tune it up, but now its much smoother.

Thanks for the help.
Dave.

Hello All,

Well guys I think I messed up big time on my
SC-1 After I Tuned up my Index drive with the factory procedure from W&S The turret worked fine. Then I went to tune up the X-axis and
Found out that the pre-amp boards are different from the one in my Other SC-1. it seems that my factory procedure for tuning up the Drives starts at machines M-5000 Lot-567 and my machine that I am fixing up is a older M-5000 Lot- 561 So since I fiddled with The amp board, the x-axis now runs worse than before! What I Really need now is the Alignment Procedure for the older Lot-561 Machine that uses the pre-amp board # 8940-754 Does anyone
Know of anyone who might copy or sell me one?? I am going to Call around to my sources and see, but any help is very greatly Appreciated.

PS: How about it John? Do you have any old info on this ???


Thanks
Dave.

I almost certainly do but will have to dig for it. I will get back to you.
John

Hi John,

Hope you can find it, all of my sources
dont have it...

Dave.

Check your e-mail Dave. I just need to know how you want it.
John