Heat Coil Presto 1-c

[Simon]

Ok max 3.7 volts

You need to be able to regulate the power - I use a lab power supply

[piaptk]

Ok max 3.7 volts

You need to be able to regulate the power - I use a lab power supply

I do have a power supply (the HP6203B Markrob recommended) and it worked fine and then all of a sudden it didn't work (i had taken out the stylus to check the tip under a microscope) and I found out that one of the wires had broken. So I put in a new stylus (and didn't untangle the wires (may have had the heat up pretty high as well)) and it just flashed, burnt up and disappeared... Is the tangling the problem?

[Simon]

yep you can not short the wires.

[maniman]

Hi to all , Retaking that issue ... is possible get an easy clear schema of what must wire that system (ps board + transformer + heat sink) , where the resistors are wired ?

i must asume the really important is regulated voltage or regulated current ?

the ps pot changes the voltage , but how to change the intensity ?

Sorry for newbie questions , maybe that type of schemas / "how to s" would be a good contributiont to the wiki , not ?

[Serif]

Hi to all , Retaking that issue ... is possible get an easy clear schema of what must wire that system (ps board + transformer + heat sink) , where the resistors are wired ?
...

I have the drawings, here, of The Lathe's Control Panel. The stylus heat control is given a regulated 24 volt source and this is attenuated with a 220k Ohm continuously variable potentiometer. Fwiw, the Vishay Sfernice looks fer-y-nice:

http://www.newark.com/vishay-sfernice/pe30l0fr224kab/potentiometer-220k-potentiometer/dp/24M5762




- Chip Swarf

[markrob]

Hi,

220K sounds way too high of a value. You qre looking to limit current to a value in to 500ma. range. With a 24V supply, that would imply a resistance in the 50 ohm range. Is this pot used in conjunction with a solid state regulator tio set either output voltage or current limit?

Mark

[aussie cutter]

I havn't got schematics but here's a couple pics my heating system on my presto 1-c

http://www.flickr.com/photos/70504575@N03/7252252828/in/photostream/

http://www.flickr.com/photos/70504575@N03/6394545023/in/photostream/

http://www.flickr.com/photos/70504575@N03/6936635943/in/photostream/

I built my heating system using markrobs suggestion of a dc power supply - i also checked out some photos posted in the past by other members and went from there...

I'm not using a pot dial or resistor - i just adjust the current on the supply

What mark says about the value being ideal at around 500ma is bang on the money - when my system is running i'm running it at 500ma and the voltage floats at around 1.5v - the cutting needle gets hot to touch, but not hot enough to burn my finger...

[maniman]

i wanna to put in a 1 x 19" rack , the LM317 based ps seems better option ( at least better than a shoes box size ps ) , i must assume simply short the ps output wires around the stylus shank ? and start to open the regulator pot ?

Thanks.

[markrob]

Hi,

If you want to keep it simple, just use a 6.3Vac transformer of suitable size (say 10VA) with a pot, series resistor (to limit max current) and an analog or digital ammeter. If you assume the stylus runs at about 2V and 500ma. (4 ohm load), and with a 6.3Vac secondary, you want the series resistor to limit the current to 1 amp, then select an 2 ohm 5 watt resistor. The pot would need to be in the range of 50 ohms 5 watt. This would give you an adjustment range of about 100ma to 1000ma. You can play with the two values to obtain a current range that you prefer.

If you go the LM317 route, it would be a good idea to use a circuit with adjustable current limiting (a meter is still useful).

The advantge of the HP supply (or other similar supply) is that when setup correctly as a constant current source rather than as a constant voltage source (the normal way the supply is used), you protect against burnout if the two heater wires short. If the supply is not current limited to a safe value, the short will cause excessive current to flow and a burnt heater results.

Mark

[Serif]

Hi,

220K sounds way too high of a value. ... Is this pot used in conjunction with a solid state regulator tio set either output voltage or current limit?

Mark

Sorry... The value is actually 20 k Ohm. It happens to be R2 in the drawing, and since there was no space between the "R2" and the "20k," it reads like, "R220K ADJ." So, I was thinking I was reading short-hand for, "Resistance: 220 K; adjustable..."

The Spectra Precision pot, itself, does say, 20k, on its body.

Still, too much resistance for I = E/R to produce the target juice...

However, since the ~600 mA current you are wanting to see is quite possible when the multi-turn wiper is moved only about 180 degrees CW, there must be more afoot...

Indeed, the drawings go further and show that the signal at the wiper of the three-pin control panel potentiometer goes into the the card cage and arrives at the base of a 2N 3773 transistor. So, it's ultimately able to get up in the 400-800 mA range without breaking a sweat. Buffered with gain.


- Reed B. Tweane

[uvoscillator]

hi ! only electrical parameters here, do anyone try to measure or calculate temperature that needed ? thanks

[Serif]

Hi, I'd like to know this, too. You could try shooting the wire with a temperature-sensing laser guided thermometer. Otherwise, the probe would sink some of the heat. Calculations seem to require knowledge of the NiCh mass, specific heat, change in electrical energy (kinetic) in Joules, and results given in Kelvin. However, the length and gauge used is so similar, since it is usually already mounted by Transco or Adamant, that ball park charge flow rates are effective when fine-tuned by ear.

As long as the record hiss gets quieter and the need for diameter eq is minimized, let the stylus heat be minimal.



Check out what Robt. Runstein writes, in _Recording_Techniques_:

"...Heating the stylus has virtually eliminated the need for diameter eq because discs cut with a hot stylus exhibit losses of only 2 dB at 8 kHz on inner grooves. This is a small loss as opposed to the 6- or 8-dB loss at the same frequency and groove diameter with a cold stylus, without diameter eq. Some cutting rooms (B.W.?) still use diameter eq even with hot stylus cutting in order to recover the last 2 dB of high frequencies otherwise lost on the inner grooves.
"The smoothing effect of the hot stylus produces a signal-to-noise ratio which improves as groove diameter decreases. The signal-to-noise ratio of a disc cut with a cold stylus, on the other hand, worsens with decreasing groove diameter. Discs cut with a hot stylus are 2 dB quieter than discs cut with a cold stylus at the outer grooves and 18 dB quieter on the inner grooves. In addition, the smoothing action virtually eliminates groove modulation noise... A hot stylus cuts through the lacquer coating of the recording disc much easier than a cold stylus, facilitating the cutting of lacquer discs that have hardened due to age. A cold stylus would produce inferior grooves called "dry cuts" on a hard disc. The stylus heat also eliminates the horns caused by the elasticity of the lacquer. Horns are raised edges on the sides of the groove which are easily broken and can cause the groove walls to break or crack when the finished record is removed from the press, resulting in increased surface noise. If horns occur on a disc, they are removed by polishing the molds used on the presses. Since horns limit the level that can be cut on a disc, higher levels can be cut with a hot stylus.
"Stylus heat must be carefully set because too much heat can cause horns to form and the wrong amount can reduce the signal-to-noise ratio. Heater current is set by listening to the cutting head feedback outputs (or pickup riding in the just-cut groove, during the disc recording) and adjusting the current for minimum sputtering noise. Since groove velocity is constantly decreasing as the disc is cut, the heat applied per unit area progressively increases. As a result, lowest noise occurs only at the groove diameter at which the current was set. Ideally, heater current should decrease as the disc is cut. The signal-to-noise ratio of a lacquer master made with a hot stylus and a negative feedback cutting head is about 70 dB, but the plating process used in manufacturing of the finished records degrades this figure by adding ticks and pops to the signal."


Adam Ain't

[uvoscillator]

wow, thanks for details, can you upload this book or tell what is exact edition, I've google, but only modern editions anywhere

[Serif]

Hi, This book is very neat, but I haven't seen it around. Somebody gave it to me. It was first printed in 1974, but I have the eleventh printing version from 1983.

ISBN: 0-672-21037-1.

Library of Congress Catalog Number: 73-90292.


I know it's expensive, but I assure you that it's well worth the 100 pennies plus shipping:

http://www.abebooks.com/9780672210372/Modern-Recording-Techniques-Runstein-Robert-0672210371/plp

The author was Chief Engineer and Technical Director of Intermedia Sound Studios, Boston, probably in the '70s.

I thought it interesting that he mentions the starting spiral (6-10 LPI) as distinct from the Lead In. One to three revolutions recommended for ss. This helps auto-dropping pickup styli find the path. He then wants a "Lead In" to follow, having unmodulated Base Pitch for at least one rev.


This reminds me of the difference between the word, Entree, in French and American usages. The Americans think the Entree is in the middle of the meal. But the French know that it is merely the "entry" to the meal. The main course is le plat principal, oui?


Also, Runstein describes a Lead Out groove, at Base Pitch for one rev, followed by a "spiral out," which is what he calls the fast groove that leads to the locked groove.

The LS-76 calls the starting spiral, the Lead In, and the spiral out, the Finish, which includes out-spiral and locked groove. The LS method works, but I like Runstein's grooviness.

The other must-have book is the two part AES Anthology on Disk Recording. Also, it's great to look at the book, Basic Disk Mastering, by Larry Boden (from here in Cincinnati - where he was at Rite Records until just after the SX-68 appeared) which I have on .pdf format.



Andre

[uvoscillator]

Thanks Andre, I'll create list to find and read !