strobe disk built into the platter & strobe lots o questions

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scrapjack+
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strobe disk built into the platter & strobe lots o questions

Post by scrapjack+ » 13 Jun 2018 18:22

Aa) Backstory
I'm reconsidering an old idea, to use a typical turntable platter for a diy transcription disk player and placing a larger tray on top only when I want to play anything larger than 12". I do rather like the dots on the side of my SL-Q2 and understand they are for the quarts lock speed control. I wouldn't mind using a platter with a built in strobe disk and providing continuous power to a strobe with a prism even if it only serves for visual inspection. Looking at pictures, the Pioneer PNR-114 platter seems to have a nicer shallow slope and 4 sets of dots, I assume for the traditional 4 speeds. However, I also looked at the platter for the Technics SL-235, which also has 4 sets of dots, surprisingly though, the spacing seems different from the spacing on the Pioneer PNR-114 platter. I haven't seen any technical documents in the archive here about built in strobe based speed control, I suspect it was considered a trade secret when a new technology.

Ba) Notes
-I'm traveling so I can't examine my Technics at the moment.
-This site lists 4 types of speed control in the database menus; quarts locked, servo
controlled, electronic(sounds vague), and synchronous.
-If I'm not mistaken strobe disks are dependent on frequency rather than diameter.

Ca) Questions
1) Do these rows of dots have a technical/common/trade name(s)?
2) Can the rows of dots on the side of a platter coupled to a strobe of the mains frequency be used as a traditional strobe disk?
3) Are rows of dots on the sides of platters used for any method other than quarts lock?
4) Are the rows different from one model to the next for any reason, if so why and how do they work?
5) If a platter has 4 rows is it safe to assume they represent each of the 4 traditional speeds, 16,33,45,78 R.P.M.
6) Theoretically could I remove the rubber strip with the rows of dots from two 12" platters and mount them back to back on a custom 20" platter, cutting to fit, to produce a Pathe capable platter with a working built in strobe disk?

Bb) Notes
-Most of my experience with strobes is either re-purposing the pumpkin 3 led light circuit, or with photography strobes, neither of which I suspect are anything like the continuous single bulb strobe circuits in turntables.
-I know camera strobe bulbs often require high voltage to operate and burn out quickly if repeatedly flashed at too fast of a rate.
-Some strobe lamps, aside of course from the lamps on studio strobes, seem to be non-standardized and perhaps hard to find replacements for when they eventually burn out.
-It has been explained somewhere on this site that the strobe light used for a strobe disk should ideally use the same voltage frequency as the turntable motor, not sure how this applies to dc, or spring and kerosene powered tables however, I digress.
-I have no experience with Arduino, I do however have recent experience with MS-DOS and soldering irons, and a variable(mechanical) timer relay

Cb) Questions: The following are assuming I have no qualms about splicing an additional transformer in parallel to the turntable mains input, and devising a way to mount the new transformer internally. If I wanted to use a strobe bulb and prism salvaged from one turntable on a table of a different model for the purpose of using side dots as a traditional strobe disk...
1) If it had long leads and wasn't firmly attached to the table could a quarts lock strobe with prism be used to view a standard paper strobe disk? Could a "built in" strobe and prism designed for a speed control other than quarts lock be so used, if so which types of control?
2) What should I look for in the part chosen, aside from good price of course? :D Is there anything that especially improves some lamps over their alternatives? For example should I limit my consideration to examples with an isolated driver board or a large heat sink, a specific type, shape, size, or voltage of bulb? What is the stuff that would make incorporating it without building/purchasing additional parts easier while permitting a long service life.
3) Do turntable strobe bulbs have a typical voltage/amp range?
4) Do they require anything more than a transformer for their power supply,(regulated power supply or blocking diodes perhaps) or any unique parts (smart programmed driver board as apposed to mechanical blinker relay) to function properly?
5) Does the angle of the strobe prism have to precisely or even closley match the angle of the side of the platter? As mentioned the pioneer has shallow slopes while the Technics looks nearly vertical.
6) Considering all factors (price, availability, longevity of vintage bulbs/parts, etc.) Should I be considering instead to simply use a prism off a turntable and a more common lamp with a focusing reflector, and a generic off the slow boat driver circuit, or simple home made circuit?
7) Was there ever a turntable with a green strobe.
8 ) Were some turntable prisms glass or quartz, or were all of them plastic/acrylic and similar?

Woodbrains
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Re: strobe disk built into the platter & strobe lots o quest

Post by Woodbrains » 13 Jun 2018 18:43

Hello,

To a answer one question, the strobe markings are dependant on the electricity supply you use the table with. 2 are for 60 Hz supply and 2 for 50 Hz supply. You disregard the 2 that you can't use.

Mike.

chiz
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Re: strobe disk built into the platter & strobe lots o quest

Post by chiz » 13 Jun 2018 19:29

On the Technics SL-1200MK2 and similar models (quartz locked) the four rows show normal speed (the big dots) and some percentage values above and below this.

Technics calls them strobe dots in the manual.

The strobe is not the mechanism used to control the speed of the platter, it's just there for a visual indication.
IMG_7982_.jpg

scrapjack+
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Re: strobe disk built into the platter & strobe lots o quest

Post by scrapjack+ » 13 Jun 2018 22:02

chiz wrote:On the Technics SL-1200MK2 and similar models (quartz locked) the four rows show normal speed (the big dots) and some percentage values above and below this.

Technics calls them strobe dots in the manual.

The strobe is not the mechanism used to control the speed of the platter, it's just there for a visual indication.
The attachment IMG_7982_.jpg is no longer available
Interesting, the Technics SL-235 platter has four rows of dots that all look like the same dots, so I found the manual this one has and it is as @Woodbrains said, this model was 50/60 hertz. Neither English manual for my SL-Q2 mentions the dots at all.


the Pioneer PNR-114 does not have a page in the database here, so if anyone has some documentation to expand the database that'd be great.

So some strobe dots are apparently standard strobe disks, and others are percentage error, so several of my questions are answered.
Attachments
strobe dots.jpg
strobe dots.jpg (95.93 KiB) Viewed 131 times

Coffee Phil
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Re: strobe disk built into the platter & strobe lots o quest

Post by Coffee Phil » 13 Jun 2018 22:27

Hi Scrapjack+,

You have a few questions here. First off you don't need to put a tray on top of your player to play large discs. My Mister Disc has a 3 1/2" platter and it plays 12" Lps just fine.

Here is a 14" Pathe playing on my Beogram 3000. As you can see it is a tight fit to the arm pivot and control knob at the left:

[img]32911[/img]

You will need an arm long enough to accommodate the largest disc which you plan to play. I believe transcription discs can be a large as 24" in diameter. You first have to decide on the largest diameter disc you will play and secure a suitable arm.

Are you interested in only transcription discs or legacy discs of all sorts. I believe the bulk of transcription discs will be 33 1/3 or 78.26 RPM. Other old records could be anything. For those you will want a variable speed machine. A non quartz lock direct drive is the easiest to hack to do that although the record you see above is 80 RPM playing on a belt drive. It is seriously hacked however.

The number of marks on a strobe disc depends on the speed desired and the frequency driving the strobe lamp. On this sits are strobe discs which you can print for the standard speed and mains frequencies of 50 and 60 Hz. The actual flash rate for a neon is twice the mains frequency. The strobe in some quartz locked turntable is driven from the quartz clock as opposed to the mains.

Phil

scrapjack+ wrote:Aa) Backstory
I'm reconsidering an old idea, to use a typical turntable platter for a diy transcription disk player and placing a larger tray on top only when I want to play anything larger than 12". I do rather like the dots on the side of my SL-Q2 and understand they are for the quarts lock speed control. I wouldn't mind using a platter with a built in strobe disk and providing continuous power to a strobe with a prism even if it only serves for visual inspection. Looking at pictures, the Pioneer PNR-114 platter seems to have a nicer shallow slope and 4 sets of dots, I assume for the traditional 4 speeds. However, I also looked at the platter for the Technics SL-235, which also has 4 sets of dots, surprisingly though, the spacing seems different from the spacing on the Pioneer PNR-114 platter. I haven't seen any technical documents in the archive here about built in strobe based speed control, I suspect it was considered a trade secret when a new technology.

Ba) Notes
-I'm traveling so I can't examine my Technics at the moment.
-This site lists 4 types of speed control in the database menus; quarts locked, servo
controlled, electronic(sounds vague), and synchronous.
-If I'm not mistaken strobe disks are dependent on frequency rather than diameter.

Ca) Questions
1) Do these rows of dots have a technical/common/trade name(s)?
2) Can the rows of dots on the side of a platter coupled to a strobe of the mains frequency be used as a traditional strobe disk?
3) Are rows of dots on the sides of platters used for any method other than quarts lock?
4) Are the rows different from one model to the next for any reason, if so why and how do they work?
5) If a platter has 4 rows is it safe to assume they represent each of the 4 traditional speeds, 16,33,45,78 R.P.M.
6) Theoretically could I remove the rubber strip with the rows of dots from two 12" platters and mount them back to back on a custom 20" platter, cutting to fit, to produce a Pathe capable platter with a working built in strobe disk?

Bb) Notes
-Most of my experience with strobes is either re-purposing the pumpkin 3 led light circuit, or with photography strobes, neither of which I suspect are anything like the continuous single bulb strobe circuits in turntables.
-I know camera strobe bulbs often require high voltage to operate and burn out quickly if repeatedly flashed at too fast of a rate.
-Some strobe lamps, aside of course from the lamps on studio strobes, seem to be non-standardized and perhaps hard to find replacements for when they eventually burn out.
-It has been explained somewhere on this site that the strobe light used for a strobe disk should ideally use the same voltage frequency as the turntable motor, not sure how this applies to dc, or spring and kerosene powered tables however, I digress.
-I have no experience with Arduino, I do however have recent experience with MS-DOS and soldering irons, and a variable(mechanical) timer relay

Cb) Questions: The following are assuming I have no qualms about splicing an additional transformer in parallel to the turntable mains input, and devising a way to mount the new transformer internally. If I wanted to use a strobe bulb and prism salvaged from one turntable on a table of a different model for the purpose of using side dots as a traditional strobe disk...
1) If it had long leads and wasn't firmly attached to the table could a quarts lock strobe with prism be used to view a standard paper strobe disk? Could a "built in" strobe and prism designed for a speed control other than quarts lock be so used, if so which types of control?
2) What should I look for in the part chosen, aside from good price of course? :D Is there anything that especially improves some lamps over their alternatives? For example should I limit my consideration to examples with an isolated driver board or a large heat sink, a specific type, shape, size, or voltage of bulb? What is the stuff that would make incorporating it without building/purchasing additional parts easier while permitting a long service life.
3) Do turntable strobe bulbs have a typical voltage/amp range?
4) Do they require anything more than a transformer for their power supply,(regulated power supply or blocking diodes perhaps) or any unique parts (smart programmed driver board as apposed to mechanical blinker relay) to function properly?
5) Does the angle of the strobe prism have to precisely or even closley match the angle of the side of the platter? As mentioned the pioneer has shallow slopes while the Technics looks nearly vertical.
6) Considering all factors (price, availability, longevity of vintage bulbs/parts, etc.) Should I be considering instead to simply use a prism off a turntable and a more common lamp with a focusing reflector, and a generic off the slow boat driver circuit, or simple home made circuit?
7) Was there ever a turntable with a green strobe.
8 ) Were some turntable prisms glass or quartz, or were all of them plastic/acrylic and similar?

scrapjack+
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Posts: 204
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Re: strobe disk built into the platter & strobe lots o quest

Post by scrapjack+ » 14 Jun 2018 01:38

Coffee Phil wrote:Hi Scrapjack+,

You have a few questions here. First off you don't need to put a tray on top of your player to play large discs. My Mister Disc has a 3 1/2" platter and it plays 12" Lps just fine.

Here is a 14" Pathe playing on my Beogram 3000. As you can see it is a tight fit to the arm pivot and control knob at the left:

[img]32911[/img]

You will need an arm long enough to accommodate the largest disc which you plan to play. I believe transcription discs can be a large as 24" in diameter. You first have to decide on the largest diameter disc you will play and secure a suitable arm.

Are you interested in only transcription discs or legacy discs of all sorts. I believe the bulk of transcription discs will be 33 1/3 or 78.26 RPM. Other old records could be anything. For those you will want a variable speed machine. A non quartz lock direct drive is the easiest to hack to do that although the record you see above is 80 RPM playing on a belt drive. It is seriously hacked however.

The number of marks on a strobe disc depends on the speed desired and the frequency driving the strobe lamp. On this sits are strobe discs which you can print for the standard speed and mains frequencies of 50 and 60 Hz. The actual flash rate for a neon is twice the mains frequency. The strobe in some quartz locked turntable is driven from the quartz clock as opposed to the mains.

Phil
I am interested in "legacy discs of all sorts," I have 16" records and records that have audio recorded down to 1" from the spindle. I've only seen transcriptions between 10-16" in diameter. As far as I was aware the largest "records" were 20" Pathe disks from sometime prior to 1925, I doubt I'll be able to ever be able to get a hold of one, however I like keeping my options open. I have only seen 33.3 and 78 rpm transcription disks however some are vertically cut. As I understand these can be played with a double pole double throw switch and a stereo cart.

I'd like to use a linear tracking tone arm as at one point I figured it would solve allot of problems with such a large playing range. I am having difficulty planing a tone arm of that size, several materials I've purchased proved to be less suitable than I hoped.

I know strobe disks are available here, I also have the program to create unusual speed strobe disks, however having the dots on a sloping platter side I thought was a nicer look than a vertical wall of plain steel like my extra platters are.

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Re: strobe disk built into the platter & strobe lots o quest

Post by gridleakrick » 14 Jun 2018 11:48

Also, note that some/many quartz lock turntables do not flash their strobes at the AC line frequency (50 or 60 Hz.). Rather, they use a quartz crystal oscillator to drive the strobe which, therefore, has no reference to the line frequency at all. In that case, the dots on the edge of the platter are specially spaced for the particular oscillator frequency and will not work with a neon bulb driven from the AC line.
Rick

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Re: strobe disk built into the platter & strobe lots o quest

Post by scrapjack+ » 15 Jun 2018 22:22

So I think all my questions about the marking have been answered. technics calls them strobe dots and they vary from model to model within brand, can be proprietary quartz lock based patterns, or standard strobe dots, not necessarily related to speed control. 4 rows of dots is more likely to mean it's patterned for 50 and 60 hertz as apposed to being patterned for 4 speed players, and the patters likely change with diameter so they cannot simply be laid back to back.


Ca) answers
1) Technics calls them strobe dots, other names might exist.
2) Some dots work with the mains strobes some will not.
3) Yes, some are purely strobe disks without effect on motor speed
4) Yes, some have percent error dots, some have 50/60 strobe dots, some are odd proprietary patterns based on quartz control.
5) 4 rows is often just 33/45 at 50 & 60 hertz respectively.
6) ---Probably not

I can't create rubber molding or print on machine parts. So salvaging it from another platform was ideal. Looking at some other strobe disks I found that the lines are actually wedges so the spacing will change with diameter.

One example.
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strobe wheel.jpg
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