Dissappearing grooves!

[punkrock]

Again, I'm having a problem with my Vinylrecorder:

Maybe you know what's happening...

When I cut a Lp (33 r.p.m.) problem happens on the first few grooves of the record. The first 2 or 3 grooves completelly dissappear just on one small sector of the record, maybe just a 10º space, the other 350º of the record are perfect. The next 10 - 20 grooves are cut much more superficially than the rest on that same sector.
Always the same sector of the vinyl. Then, the rest of the record is perfect. I've checked the turntable and it's perfectly balanced, the cutting needle weight is set at the required weight, the record temperature is above 40 º celsius, I'm spreading the surface denoiser liquid ALL over the record, I'm not missing any space...

This morning I tried to cut a 45 r.p.m. 7i. This time happens at the end of the record. The beggining is perfect then on the last few grooves a small section dissappears! Always the same section!

I can't find the mistake/problem/whatever. Any ideas?

Could it be that the cutting needle isn't set at the correct angle?

[The Shank]

Maybe some unflexibility around your dashpot. It must be able to move and very flexible (up and down and a bit left/right too)

[tragwag]

what material are you cutting?
extruded polycarbonate should be totally (mostly) flat
pressed PVC has a contour to it. search the RIAA standard for pressed records to see the dimensions.
keep this in mind!

[punkrock]

what material are you cutting?
extruded polycarbonate should be totally (mostly) flat
pressed PVC has a contour to it. search the RIAA standard for pressed records to see the dimensions.
keep this in mind!

I already thought this... Apparently they're completely flat, but I guess something like half a millimeter or less is hard to see at normal sight.

I'm cutting Souri's blanc records, I've had them for two years now at home. Stored them vertical.

I'll try three things tomorrow: a) First I'll try to set again the cutterhead and stylus just in case it's an "angle" problem. This afternoon I remembered I once set a cartridge on a Linn Akito tonearm in a slightly wrong angle and it would play Lp's but when playing 45's it would violently bounce back. I suppose it was because of the centrifugal force (not the anti-skate).

b) I'll try a new stylus. The one I'm using now looks perfect anyway.

c) Just received a few blanks last week. I can try one of those.

[punkrock]

Maybe some unflexibility around your dashpot. It must be able to move and very flexible (up and down and a bit left/right too)

By dashpot you mean the cutterhead attachment? Seems to be perfect, I even re-lubricated the moving parts just in case. But there's one thing which annoys me, Souri gave me a dinamometer to set the correct weight for the cutting stylus. As it a quite imprecise method I'm actually using a precision balance... If I try to check the weight ten times in a row I NEVER get the same value twice, it can vary up to two grams or more each time!

[audadvnc]

I ran into a similar situation last year that was a combination of the lacquer not sitting flat on the turntable and upward pressure from the vacuum hose (from having been inserted too far, thus pulling back on the head). Once I reseated the vacuum hose and found the cause of the non-flat lacquer (a smidge of scotch tape on the turntable) everything was back to normal.

A dashpot is a piston mounted between the head and head arm chassis that is filled with oil, designed to act similar to a shock absorber on a car. I've never used the dashpot on my Scully/Westrex machine, it's in place but not filled with oil.

[SUNBEARS]

Are you using Souri's automatic switcher?? Sometimes the sensor gets too close to the counter weight arm.. Especially if you are switching thicknesses.. For example from a 2mm disc to a flexi... Counterweight arm goes up higher and the sensor for auto switcher can limit the range of vertical movement of the cutterhead..

Good luck!

[punkrock]

Are you using Souri's automatic switcher?? Sometimes the sensor gets too close to the counter weight arm.. Especially if you are switching thicknesses.. For example from a 2mm disc to a flexi... Counterweight arm goes up higher and the sensor for auto switcher can limit the range of vertical movement of the cutterhead..

Good luck!

Nope, I don't have it. Everything manual...

I think I discovered the reason I had this problem: I bought those blanks a couple years ago, the last ones seem to be a bit warped, very little, but they're warped, specially on the outer rim. So, when the cutting needle gets to the top of the warp it will sometimes "fly" instead of keeping in touch with the record and groove will dissappear.

[SUNBEARS]

More weight!! Unless it's super drastic!

[punkrock]

Sure! I already thought that, but I'm cutting without the extra motor, I'm only using my Technics turntable. If I add weight to the cutting stylus the Techhnics motor will slow down and distortion will appear.

This, in my opinion is the biggest problem with Souri's cutter: the basic equipment will make cutting more difficult. I'm not a pro, I just bought the Vinylrecorder because I'm record collector, turntable collector and vinyl enthusiast en general, so I don't do this for a living but as a hobby. But once I have 1000 euros to burn I'll definitely buy that equipment.

[The Shank]

Add a 1,5 ohm resistor into the turntable and your problem is gone ^^

[punkrock]

Add a 1,5 ohm resistor into the turntable and your problem is gone ^^

My electronics knowledge is virtualy zero... That will add torque? Where should I add it? Won't it ruin my turntable in some time?

[Gus]

Maybe your platter wobbles.
Dissappearing grooves remembers me my own Stanton ST-150 with wobble platter too.
First of all check the platter of sl-1200

https://www.youtube.com/watch?v=gM3S-owyPNQ


if it wobbles then check this video maybe helps you to solve the problem

https://www.youtube.com/watch?v=qLOjUADMNlE

[Gus]

for modification to add more torque into Technics mkii

check this thread, but do not try it if you don't have the basic knowledge of Electronics

http://www.lathetrolls.com/viewtopic.php?f=9&t=4709

[duomo]

perhaps its your damping. the little metal disc should sit completly in the oil, without air bubbles. the head is a little stiffer than and can not jump so easy. you need 15- 20 grams then.
good luck