VR pvc blank shelf life

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VR pvc blank shelf life

Unread postby okpanda » Wed Aug 09, 2017 5:36 pm

i'm having trouble cutting a groove on my VR everything worked perfectly a few months ago, until i took everything apart and changed my setup. i've calibrated everything i can think of but when i try to cut an unmodulated groove, the playback needle won't even stay in it, it hops out and slides across the record. i'm using a brand new stylus, weight is set properly, disks are heated to 40C using an infrared lamp, cutterhead and stylus are properly aligned, etc. i even thought it might be my playback needle, so i got a new one. my blanks have been sitting in a hot garage, is it possible that they have gone bad? the only other variable that has changed is my lamp, since i switched from a white bulb to an infrared reptile bulb from the pet store. could the infrared light possibly be damaging the surface of the disk? i know it's a stretch but i'm out of ideas, please help!
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Re: pvc blank shelf life

Unread postby SueDenim » Wed Aug 09, 2017 6:04 pm

What does the unmodulated groove look like under the scope?
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Re: pvc blank shelf life

Unread postby okpanda » Wed Aug 09, 2017 6:47 pm

it's hard to describe, but i see little white spots, which i fear might be bubbles or something in the vinyl. the grooves themselves look normal i guess, just straight lines since they are unmodulated.
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Re: pvc blank shelf life

Unread postby SueDenim » Thu Aug 10, 2017 5:01 am

OK, well if you're absolutely sure that everything else is set correctly (e.g. weight, angle, stylus) then the next thing to do is buy a few more new blanks and try again.
I think that's the only way to rule out the blank as the problem.
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Re: pvc blank shelf life

Unread postby TheCrates » Thu Aug 10, 2017 8:02 am

To be sure, try a new one like Sue recommend, always worth a try.

Does your playback tonearm skip/jump with older cutted records, and tried another turntable with both records? In case it does, check your your tonearm playback setup/calibration once more.

Image how much scratching you can do before a needle skips, there must be a huge visual difference in the groove somewhere.
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Re: pvc blank shelf life

Unread postby The Shank » Thu Aug 10, 2017 1:38 pm

Gavin, you would be my best technical support ever. I have tons of questions for you everyday hahaha!
http://www.myshank.com
skype : steven.myshank

* Diamond cutting stylus officials/prototypes
* Resharpening services
* Blank records
* Cutting lathe
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Re: pvc blank shelf life

Unread postby SueDenim » Thu Aug 10, 2017 3:22 pm

Just telling it like it is Steven ;)
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Re: pvc blank shelf life

Unread postby okpanda » Sat Aug 12, 2017 1:43 pm

just wondering if there's anything else i can rule out before the blank, or if it's even realistic to wonder if the blank is the issue.
i just noticed my platter is not very front-to-back level, maybe that's the problem.
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Re: pvc blank shelf life

Unread postby tragwag » Sun Aug 13, 2017 3:04 pm

uneven platter would certainly cause that.
have you checked your cut on other turntables? and compared it to your last successful cuts under the scope?

I've kept some blanks for over a year, they were either test blanks, or large hole that I sat on for a while until I wanted to offer them.
Had no issues in either case.
making lathe cuts on a Presto 6N, HIFI stereo cuts on vinylrecorder
at Audio Geography Studios, Tallahassee, FL USA
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Re: pvc blank shelf life

Unread postby okpanda » Wed Aug 16, 2017 8:41 pm

the platter was about a centimeter off from being level but i balanced it out. the grooves look good under the microscope. i can play commercially pressed records without any problem, so i assume my playback turntable is fine. really at a loss as to why i still can't cut a playable groove :(
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Re: pvc blank shelf life

Unread postby SueDenim » Thu Aug 17, 2017 4:34 am

when i try to cut an unmodulated groove, the playback needle won't even stay in it, it hops out and slides across the record

If you watch the playback stylus closely, does it actually jump out of the groove as though it has hit something, or is it more like it slides but never loses contact with the record?
The latter would suggest a groove depth issue which you should be able to see through the scope I would have thought.
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Re: VR pvc blank shelf life

Unread postby tragwag » Thu Aug 17, 2017 3:46 pm

does the chip pickup ok? if it does, I would think your depth and stylus are somewhat in a good range.
If you have dropped chip you may be losing contact with the disc (not enough depth) or the stylus is in bad shape, misaligned, or something else
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Re: VR pvc blank shelf life

Unread postby okpanda » Sat Aug 19, 2017 4:35 pm

the playback stylus just slides across. the grooves look fine, not broken or anything. no way of measuring how deep they are but weight and heat are at known good settings. i guess i could increase my weight for deeper grooves but that doesn't seem right. i set my cutterhead weight to 45g/~16g as suggested for a new stylus. blanks are heated to 40C and treated with souri spray. cutterhead is parallel and platter is level. stylus is straight and firmly inserted. what am i missing?
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Re: VR pvc blank shelf life

Unread postby okpanda » Sat Aug 19, 2017 4:36 pm

chip suction is fine. i have followed the vr tutorial on myshank's page (thanks for that, steven! invaluable!) and upgraded to a real vacuum pump. everything seems like it should be working really well.....
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Re: VR pvc blank shelf life

Unread postby handcut » Sun Aug 20, 2017 6:22 am

okpanda wrote:platter is level.


Sorry for the possibly silly questions but is your lathe level? Not the platter, but the base of the lathe itself. Have you checked that the dashpot is not 'bottoming out'? Also, when did you last strip and re-grease your TT bearing? That last one can catch you out, with the Technics 12xx TT's at least... An unhappy bearing can cause subsonic resonances which in turn can activate tonearm resonance.
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Re: VR pvc blank shelf life

Unread postby tragwag » Mon Aug 21, 2017 4:47 pm

you gotta get a microscope to see what's really going on. and double check your head weight, I'm usually closer to 20 grams for a 2-3 mil groove
making lathe cuts on a Presto 6N, HIFI stereo cuts on vinylrecorder
at Audio Geography Studios, Tallahassee, FL USA
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