VMS-70 // SX-74 Cutterhead Release Problem

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phax
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VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28146Unread post phax
Thu Dec 19, 2013 10:50 am

hi folks,

i have a weird phenomenon right now.
the sx-74 cutterhead from my neumann vms 70 doesn't release anymore automatically.
neither when the head hits the microswitch nor when i'm hitting the stop-button....!?!?
i've tried to change the PS-66 "release" setting but nothing happened.
i've already cut 4 lacquers today on different diameters and rpm's and it worked quite normal.
but now... :?

any suggestion about this?
it would help me out alot!!

thx in advance ;)

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tragwag
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28147Unread post tragwag
Thu Dec 19, 2013 11:01 am

I know Dietrich has encountered this problem on and off a lot lately. I'll let him chime in with any info
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opcode66
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28149Unread post opcode66
Thu Dec 19, 2013 12:11 pm

You need to replace one microswitch in your suspension box.

It is the one rated for 27volts. It is a different part number than the other.

It controls flow of current to the solenoid
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mossboss
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28151Unread post mossboss
Thu Dec 19, 2013 2:10 pm

Alternative or also, check that the flat part of the fiber cam does trigger the micro
Remove the plate on the side of the suspension box check it out
There are two red paint dots on the head of the screws if they have been broken it means that someone had a go at them in the past
So it is not unlikely that they may have moved or the flat spring blade lost some of its tension or that the flat part of the cam is somewhat worn or that it needs some slight adjustment
Easy enough to check it out
You would need some decent jewelers/watchmakers screw drivers though, not the cheap nasty ones from the basket at the local hardware store as they tend to damage the heads of the screws
Rarely these micros go bad to need replacement
See how you go and do lets us know
Cheers
Chris

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mossboss
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28152Unread post mossboss
Thu Dec 19, 2013 2:25 pm

Forgot to mention the solenoid that keeps the head down I have yet to see one of them go bad but there is a rather poorly made bracket with a spring that holds the lever down
This can also go out of kilter particularly of the lever is pushed up without pressing the release button up the top first
The solenoid gets activated and keeps the head down once it is lowered into the cutting position
When the stop lever at the end of the carriage travel, is hit or the release button is pushed current is cut off so the solenoid is De-activated
This solenoid pushes a catch out of the way so as to release the head
It is simple enough to remove and put back into shape
Hard to explain but once the cover is out a simple observation of how it works by lowering and releasing the head you can see what needs to be done
If it is out of shape it needs to be removed and put back into shape
That can happen when someone has put enough pressure on the lever attempting to lift the head off without pressing the release button
So here is another source of trouble that you want to have a close look at
Cheers
Chris

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phax
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28155Unread post phax
Fri Dec 20, 2013 5:46 am

thx for your feedback.
i hope i did understand your advices. when i turn down the head the microswitch and the springs are ok. they do their job.
but even when the side of the suspension box is open, it's hard for me to see what special mechanical "thing" locked the head in his downposition.

i made 2 pictures...

Image

Image

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opcode66
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28173Unread post opcode66
Sat Dec 21, 2013 12:47 pm

Well, I had this exact same issue. No automatic head release. It was fixed by replacing the microswitch that passes voltage to the solenoid. You cant see the mechanism because it is obscured. You have to drain the dash pot and open the bottom panel to see it. But, you don't have. I am pretty certain it is the switch. Not to contradict Mossy, but I've had to replace mine. Dietrich replaced his. I know of at least one other who did the same. They go bad after a number of cycles. Did you actually meter the switch while moving the lever???

Also, fyi, the diode and calacitor soldered to the switch is not standard. Someone else added those...
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mossboss
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28175Unread post mossboss
Sat Dec 21, 2013 3:03 pm

Its OK to contradict me Todd
So long we get there at the end its fine
Its only what I know from what Ive been running for years
Having 4 of them over the years, 2 currently, while maintaining them I never encountered this issue but all of the other issues I have come across, the ones I mentioned
By the looks of the photos this head suspension had a few goes at it
You are perfectly correct the diode/capacitor are not standard they should not be there either
It seems that this system had issues dropping the overload on the rack when the head was moved down due to surges or spikes
So rather than look at the O/L module a quick fix was done as the photos show
Back to the point
One can check if the solenoid is working by moving the lever slightly downwards after the head is down
If the solenoid is not energized the head will be sitting on the lever catch it will have slight movement past the catching point as you move the lever
You can tell than if the solenoid is holding the head rather than it sitting on the catch on the lever
There will be a little movement on the lever but not the head if it is held down by electromagnetic force if not you see it moving
I am sure you get the idea
Not hard to check it out
But than again all this could be just hot wind!!!
I have seen stranger things with these systems so anything is possible
Cheers
Chris

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opcode66
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28182Unread post opcode66
Sat Dec 21, 2013 6:50 pm

The doide/cap across the poles of a switch are usually done to debounce a switch.
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gold
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28192Unread post gold
Sun Dec 22, 2013 11:50 pm

If you lower the head without being in Start you sent more current through that microswitch than it is rated for. They go bad all the time. They are easy to find and replace.

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phax
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28195Unread post phax
Mon Dec 23, 2013 5:52 am

thx for all your help and advices!

i've replaced the microswitch and now it works fine again!

THANK YOU ;)

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opcode66
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28196Unread post opcode66
Mon Dec 23, 2013 10:10 am

I told ya so.... No one wants to listen to me though....
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dietrich10
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28225Unread post dietrich10
Thu Dec 26, 2013 9:38 am

Late to the party. Glad you are back cutting.

My solenoid went bad because when we took it out to repair another issue(unrelated to the microswitch the 'lever' needed tiny realignment after decades of abuse). One of the wire ends on my solenoid was so brittle with age and current damage that it became impossible to reuse thus a new solenoid had to be wound . If we did not have to take the suspension box apart it would of last another decade even in that state.
cutting lacquers-vms70 system

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opcode66
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Re: VMS-70 // SX-74 Cutterhead Release Problem

Post: # 28227Unread post opcode66
Thu Dec 26, 2013 12:13 pm

I am winding some nice coils these days. Hit me if you need a solonoid rewind, a mono cutterhead repaired or any other VMS lathe tech work done.
Cutting, Inventing & Innovating
Groove Graphics, VMS Halfnuts, MIDI Automation, Professional Stereo Feedback Cutterheads, and Pesto 1-D Cutterhead Clones
Cutterhead Repair: Recoiling, Cleaning, Cloning of Screws, Dampers & More
http://mantra.audio

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