Lead-in spec, groove guard issue // VMS 70

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Lead-in spec, groove guard issue // VMS 70

Post: # 29096Unread post prof msg
Sun Feb 23, 2014 9:48 pm

I have an issue on a test pressing with the groove guard causing a sound immediately before the audio starts. I have never adjusted the microswitches. It looks like it might be a bit off.
Also, I've always started the audio in the first half rev after lead-in, but maybe I need to leave more silence. Lead-in end diameter is 293 mm( just over 11 1/2")

I've seen reference here to the Neumann spec but can't find a number.
Checking out other records, I see that most are around 291, but there is some variance. Also seeing a lot of records with 3 or 4 seconds of silence before audio.

So what exactly is the specified diameter?
Does anyone set the diameter further in to avoid issues with swoosh and non-fill?
or manually add lead-in on a case by case basis?
or add silence after the lead-in?

thanks,
-Kevin

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opcode66
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Re: Lead-in spec, groove guard issue // VMS 70

Post: # 29098Unread post opcode66
Sun Feb 23, 2014 10:34 pm

When you say groove gaurd do you mean the safety groove?

Where that starts and where the end of the lead in groove is are two separate events.

First the microswitch in the back is never altered or adjusted in any way. The plungers on the plate that travels across the top of the microswitches are what get adjusted. The manual has clear instructions for this. But, there is a locking nut that you need to unscrew first. If you don't have the correct tool, you can use a sturdy compass. Adjusting the correct plunger will adjust where the safety groove/lead in starts (safety groove obviously being optional). The microswitch is normally closed. When the carriage passes, and it is depressed it opens therefore breaking the flow of 12V from and back to the PS66 Programmer. Inside the programmer is a soldered connection that determines which switch is sent the 12V. In my case, I have a rotary switch that allows me to select various diameters. Original boxes were fixed at one diameter.

I digress, After the 12V is interrupted, there is a very simple RC Delay (resistor/capacitor analog delay) that happens. So, the 12V fades out via the charged cap through a resistor. That delay is speed dependent (33/45). That delay is what governs the amount of time spiraling occurs for the lead in groove. Once fully discharged, normal pitch resumes.

So, if you want to change where this all starts, adjust the correct microswitch. If you don't have the manual, I'll scan and pm you the page. Just ask. If you want to look into a lead in groove that seems too short, I suggest pulling your programmer box and changing the Capacitor that is use for this delay. They go bad and then have incorrect timing. I can tell you which it is.

Finally, it should be noted that though there is a true standard on where the lead-in starts. In reality, you should really check with the plant you will be sending most of your work to. Each has its own implementation of the standard so to speak. The one I work with mostly asked me to adjust my lead-in start just a hair because it was causing issues for them when forming the stamper plate.
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Re: Lead-in spec, groove guard issue // VMS 70

Post: # 29099Unread post prof msg
Sun Feb 23, 2014 11:40 pm

By groove guard I mean the raised bump at the edge of the record. In this case it extends through my lead-in almost to the recording surface.

I hadn't considered that the delay may have drifted - I'll look into that first before anything mechanical.

I will start checking with new plants I'm sending to. In the meantime, I'm still interested in to know what the standard lead-in start/end are, or what diameters people are using most often.

thanks,
-Kevin

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Re: Lead-in spec, groove guard issue // VMS 70

Post: # 29100Unread post opcode66
Mon Feb 24, 2014 12:20 am

My start happens right around 11 3/4 inch.

The mechanical happens first. Then the electrical delay. So, if it is starting at the wrong place, you need to adjust the plunger for the microswitch. Do you have a copy of the manual with the page that explains how to make the adjustment?

I know I have a chart with the standards. Its on the back of a micropoint bulletin.
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Re: Lead-in spec, groove guard issue // VMS 70

Post: # 29101Unread post prof msg
Mon Feb 24, 2014 1:10 am

My start also happens at 11 3/4".

My manual is incomplete. That page would be very helpful.

-Kevin

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Re: Lead-in spec, groove guard issue // VMS 70

Post: # 29102Unread post opcode66
Mon Feb 24, 2014 1:51 am

I've replied with the scan of the page via PM. It should be noted that this page is available in the documents that are on this cd for sale on eBay. It is totally worth the $20.

http://www.ebay.com/itm/NEUMANN-VMS-RECORD-LATHE-OPERATION-SERVICE-MANUAL-SET-/161228816911?pt=US_Other_Pro_Audio&hash=item2589fc820f
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Re: Lead-in spec, groove guard issue // VMS 70

Post: # 29103Unread post opcode66
Mon Feb 24, 2014 3:05 am

Thinking about this. It seems odd. If you have a 1/4" to spare you shouldn't be that far out. The ruler on the front of lathe body is adjustable. Was yours properly calibrated? I.e. How do you know 11 3/4" on the ruler correlates to reality? Have you verified this?
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Re: Lead-in spec, groove guard issue // VMS 70

Post: # 29105Unread post prof msg
Mon Feb 24, 2014 12:03 pm

Yes, I'm measuring the diameters on the disk, not with the ruler on the lathe.
Also the scale on the my lathe is metric (it's from the UK) so I'm converting.

Lead-in start 299mm (11.77")
Lead-in end 293mm (11.54")

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Re: Lead-in spec, groove guard issue // VMS 70

Post: # 29106Unread post jjgolden
Mon Feb 24, 2014 12:56 pm

As a general rule of thumb. It's good practice to stay well clear of the groove guard(s).
You will find different types/thicknesses from different presses and some with none at all.
If you have the test pressing from this particular pressing plant, take note of where it starts and/or mark it on your lathe ruler.
(i.e. United/RTI/Rainbow etc..)
It's also advisable to give a few revolutions prior to audio start. Otherwise, on some automatic turntables the arm/needle will
drop and possibly bounce/skip into the audio instead of an adjacent blank groove.

2 cents :>)
JJG

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