Rapid vertical movement w VR

[jonoaustin]

Wondering if any one has seen this before. I have 3 VR's. Been cutting with 2 of them for about 6 years, I guess. Added the 3rd a couple months ago. One of them started exhibiting this behavior a couple weeks ago - couldn't figure it out so I took it out of commission. Now another one is doing exactly the same thing, so it's dead in the water too. Souri has no idea what could be causing this.

Outer diameter on 12" - outer 1" or so - the cutter head is cutting unmodulated grooves that rapidly go deeper and shallower....like 1-4mil. As the head moves toward the center of the record, it becomes stable. I've swapped out styli, cutter heads, main units, turntables, groove controller on/off, stylus heat on/off, external motor/belt on/off. Plate measures perfectly flat as it rotates with a pressure gauge. The change in depth has happening very quickly - maybe a couple times per inch of rotation.

Anybody see anything like this before?

j

[tragwag]

having a similar issue from time to time over here, it's been due to blanks and too much head weight.
I back off just a touch and it fixes itself.
this problem only happens on my 2nd VR, where the spring/dashpot is in worse shape

[jonoaustin]

Thank you.

[jonoaustin]

having a similar issue from time to time over here, it's been due to blanks and too much head weight.
I back off just a touch and it fixes itself.
this problem only happens on my 2nd VR, where the spring/dashpot is in worse shape

Tried varying weight lighter and heavier - no improvement. Anybody else have any ideas?

[SueDenim]

As you have the luxury of having multiple VRs I'd start by comparing the dash pot on the problem one against the dash pot on the good lathe.
Do they look the same?
Is the spring in the same position, top and bottom of the cylinder?
Is the plunger contacting the sides or is there any additional friction?
Have you tried rebalancing the head from scratch?
I might even try a test cut without the dash pot active at all (after rebalancing the main rear counter weight to give an 11g cutting force of course!) - is the problem still there/the same/different?? etc.

Best of luck!

[jonoaustin]

As you have the luxury of having multiple VRs I'd start by comparing the dash pot on the problem one against the dash pot on the good lathe.
Do they look the same?
Is the spring in the same position, top and bottom of the cylinder?
Is the plunger contacting the sides or is there any additional friction?
Have you tried rebalancing the head from scratch?
I might even try a test cut without the dash pot active at all (after rebalancing the main rear counter weight to give an 11g cutting force of course!) - is the problem still there/the same/different?? etc.

Best of luck!

Thanks. Both DP's are in good shape, seem to be operating effectively.. Good idea though, trying it with disabling the dashpot completely. Will give it a go. Thank you again. J

[2bitcomputer]

You've probably already checked this but is your lead screw well lubricated?
If I let my VR go too long between lubrication, I can see unusual patterns in my grooves.

[trailerparkjesus]

I also have this happening recently on one VR. Tried everything, new oil in dash, rebalancing, more weight less weight, oil screw... still happens every 10 records or so. It will dig deep then bounce out (not out of phase ever). I need to check stability of the bearing inside the TT. Maybe since running a heavy platter for so long its caused some kind of irregularity with the TT. Also check any resonances that might be translating through the mechanics causing a low end spike... my veneers I made were touching my work bench so I lifted them up a bit so there is isolation in case of rogue vibrations. If you havent cleaned your feedscrew, I'd do that and re oil. I just took a cloth and ran the motor while holding it to it then re oil, LOTS of dirt.

[theinhabitant]

What are you guys lubricating the lead screw with?

[jonoaustin]

I also have this happening recently on one VR. Tried everything, new oil in dash, rebalancing, more weight less weight, oil screw... still happens every 10 records or so. It will dig deep then bounce out (not out of phase ever). I need to check stability of the bearing inside the TT. Maybe since running a heavy platter for so long its caused some kind of irregularity with the TT. Also check any resonances that might be translating through the mechanics causing a low end spike... my veneers I made were touching my work bench so I lifted them up a bit so there is isolation in case of rogue vibrations. If you havent cleaned your feedscrew, I'd do that and re oil. I just took a cloth and ran the motor while holding it to it then re oil, LOTS of dirt.

Ok thanks. Did any of this work? I have 2 machines doing it....not every 10 records, but all the time. I’m going to try to clean the screw further. I oiled them once every couple weeks over the last 5 years. Seemed fine. Newest machine (less than a year) doing fine, no problem. The vertical movement is limited to the outer 1” or so and the movement is very rapid. Like a couple cycles per inch. The cut depth seems to vary 3-4 mils. If the weight is light, then 0-3, with heavier weight 2-5, etc.

[trailerparkjesus]

I just separated the veneer from touching so time will tell on that. First biggest thing to check is the precision platter (platter run out), make sure there are no sudden slope then drop in the level when testing with the pressure gauge. Do you order from MyShank? Maybe we all are experiencing a bad batch of records that are effected by some lathe set ups? No offense steven, just ruling out everything!

Tyler might be right in maybe we need to test doing the weight differently on some set ups, maybe lighter counter weight.

Also make sure all moving points are clean and oiled. One to check is the ring that the copper spacer slides into on the dash, if that is sticky from old oil or residue that can cause the dash not to operate consistently.

These are all checks Ive done and it doesn't happen as often anymore, hoping next stylus change eliminates completely. We always wish we could just do the "have you tried restarting the computer/router?" trick with the t560

[jonoaustin]

it's happening w both shank and souri blanks. black, clear, etc. so I don't think it's the blanks. with regard to platter - I check level of the carriage arm and then the platter each day. Getting no runout, etc., and the grooves are perfect after the first outer inch. It just seems like it has to be something in the screw at the first-inch location...some grime or something? Going to keep cleaning there and see of that helps.

[trailerparkjesus]

My thought too a couple weeks ago, maybe i didnt clean mine enough. Was thinking it hits a spot in the screw with crud and digs then lifts up. I noticed it in a similar region on my discs too.

Let me know if/how it goes away!

[2bitcomputer]

Maybe you guys have already tried this but, repositioning the "screw cylinder" in the uprights might help rule in or rule out the problem of a "bad screw area".
If you loosen the uprights you can slide the "screw cylinder" an inch or so further Left - if the screw is the problem, then the head oscillations should move the same amount further into the disc.

Seems like you might have something binding somewhere...?

[jonoaustin]

That’s a really good idea. Thanks!

[tragwag]

Maybe you guys have already tried this but, repositioning the "screw cylinder" in the uprights might help rule in or rule out the problem of a "bad screw area".
If you loosen the uprights you can slide the "screw cylinder" an inch or so further Left - if the screw is the problem, then the head oscillations should move the same amount further into the disc.

Seems like you might have something binding somewhere...?

Oh wow I never thought of that! I took one of my VRs apart because the pins holding the halfnut fell out
Now that I'm looking, I put it back together with the screw cylinder 2-3 inches offset from my other VR

[rubenr]

try whit diferent degree inclination.. I haved this problem to, 2 week before. And was that.

[e3sa934]

@jonoaustin ... did you resolve this?

I think I might have a similar problem, getting groove patterns like this, then ending up with a swarf spill. No music being cut, just the cutting head moving over the blank:





I've swapped diamonds, lubricated the screw, applied De-oxit to the groove controller pot, and recalibrated the cutting head. I'll try repositioning the screw cylinder as suggested by @2bitcomputer tomorrow.

Otherwise, any further thoughts, please?

[handcut]

@jonoaustin ... did you resolve this?

I think I might have a similar problem, getting groove patterns like this, then ending up with a swarf spill. No music being cut, just the cutting head moving over the blank:





I've swapped diamonds, lubricated the screw, applied De-oxit to the groove controller pot, and recalibrated the cutting head. I'll try repositioning the screw cylinder as suggested by @2bitcomputer tomorrow.

Otherwise, any further thoughts, please?

Try cleaning & relubricating the turntable bearing. This looks a lot like a resonance issue I had some years ago. I replaced the bearing and it fixed the issue, but then a couple of years of heavy cutting later it came back and strip, clean, relube fixed it. The thrust pad on a 12xx is prone to pitting, especially if you use the prescision platter.

[e3sa934]

@jonoaustin ... did you resolve this?

I think I might have a similar problem, getting groove patterns like this, then ending up with a swarf spill. No music being cut, just the cutting head moving over the blank:

I've swapped diamonds, lubricated the screw, applied De-oxit to the groove controller pot, and recalibrated the cutting head. I'll try repositioning the screw cylinder as suggested by @2bitcomputer tomorrow.

Otherwise, any further thoughts, please?

Try cleaning & relubricating the turntable bearing. This looks a lot like a resonance issue I had some years ago. I replaced the bearing and it fixed the issue, but then a couple of years of heavy cutting later it came back and strip, clean, relube fixed it. The thrust pad on a 12xx is prone to pitting, especially if you use the prescision platter.

Hmm, I'm running with a brand new 1200GR with no precision platter - do I need to adjust? Further to my initial post I've re-lubricated the screw and applied more De-Oxit to the groove control pot, and also moved the screw cylinder 4cm to the right - just about as far as it will go. I've also fitted a brand new diamond stylus and recalibrated ... and now I seem to have cured the problem (touch wood)