Rapid vertical movement w VR

[handcut]

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

Bizarrely, I'm now having this exact problem.... Only with black blanks. None of the usual tweaks seem to be getting rid of it. Very strange.

[handcut]

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)

Very unlikely to be the bearing then. The top image is almost identical to the resonance problem though. The bottom one looks more like the moire pattern one gets from rumble though. Still, you've fixed it now - congratulations!

[Ibai]

I have been with problems for a few days and I cannot solve it, neither by cleaning, lubricating or giving more weight and less weight...is this related to the same problem?

[PMST]

I have been with problems for a few days and I cannot solve it, neither by cleaning, lubricating or giving more weight and less weight...is this related to the same problem?

Have you tried changing the dashpot oil? I had the same issue, i tried everything, but in the end i took the machine apart, cleaned the dashpot out and put fresh oil in and it went away, i assume the oil was changing viscosity when old, hot and used a lot. Also have you tried ruling out the blank? i actually had a batch of blanks that had issues which really made things confusing!

[Ibai]

I’m waiting for a new oil, I think I read about type (SAE50) in some post of you
The oil is the same since the first customer boughts the VR, about 7 years, so I hope that change will benefit.
And yes, I’m discarting a lot of warped blanks, cause when they are flat there is no problem. Do you think heating them in a hot flat marble will flatten blanks?

Thanks for answering PMST,

Have a nice day all.

[PMST]

If the oil is that old i would 100% change it, mine was only 18 months old, i cut around 100 records per week and the oil had turned brown already, new oil is a good shout i'd say. I had a few records like yours where the head lifted at the same point on every rotation, but after changing to a new set of blanks that went away so could definitely play a factor, along with the dashpot oil, i think anyway from what i went through.....

What i have started doing is using blanks from the bottom of the pile, as they will be the flattest (i assume)...... Seems to work for me anyway

[tragwag]

definitely continue what you're doing already, but double check the head weight. slightly too much head weight has caused that problem for me before