100% correct stylus heating

[andybee]

hi Laquer cutters!

yesterday, I noticed a small problem with my stylus heating circuit,
and finally, I am not sure if it works 100% correctly.
As far as I know, there must be a voltage of 5V DC with an amperage
of approx. 0.4-0.5 Ampere (adjustable). (so, approx. 2 Watts)
But, I measured only 2Volt @ 0.5 Ampere, that´s only 1 Watt.
If I raise the amperage/voltage up to 0.8Ampere @ 2.4 Volt (approx. 1.9 Watts),
the groove is not looking clear anymore. (the valley looks more white)
Then, I leveled the ampere down to 0.2, I had a clear groove...
All was done with transco stylus and apollo laquers.

I am interested in the original regulation circuit for the laquer styluses, anybody
has them? I think, with mine, is something wrong...

Thanks for your help!

[Nickou]

I use 12 v and 0.45 amp
The vms66 we have is totaly original and the voltage is 12 volts
on the am32b , we use a DC power supply wich can give 2A at 12 volts,

[andybee]

thanks, oh that´s a lot more voltage!?

Do you really have the 12V voltage at the stylus?
or is it just the voltage from the power supply, that is running
through a variable resistor?
With 12V and 0.45 A, there will be 5.4 Watts, Adamant says 2.025 Watts
for the stylus heating, this is a huge difference...

still confused about that...

[Nickou]

Hi andy


Yes , around 12 volt at the head on the vms 66
I check years ago on a a vms80 , and it was also a voltage of 12 volts

I still used this voltage and a current of around 0.5 amp

if you want to use only 2 watts , you can still make tests with less than 0.2 amps .. personaly I use around 0.45 at the begining of a lp and finich around 0.55

try it ! I use transco stylus now , but with adamant it works the same

[Serif]

Hi Andreas, The Westrex manual indicates that the power required for heating the Westrex heated stylus (P9843-1) is ~6V (AC or DC) at ~0,5 Amperes. So, 3 Watts for the name brand Westrex. In fact, they say one can substitute this heater for a home made one which uses a 5 mils dia. NiChrome (32 Ohms per foot) wound 7,5 times around a no. 54 drill bit. However, for the home brew heater, they recommend 12 Volts at 1.2 Amperes. So, up to 15 Watts is not unthinkable, depending on the setup. Also, the circuit can be as simple as described, or can include, say, a transistor. The Scully LS-76 uses a 2N3773 NPN transconductance varistor which has a lot of current boost on tap.

Since there is a broad range of heater current which makes the hiss of the blank's unmodulated grooves more quiet than when using no current, and since too much heat is bad since it not only risks burning the chip and making it stick to the lacquer but can also make horns form that vex electroforming, it is best to tune the heat by ear, rather than by numbers.

Drop the tonearm in the newly forming unmodulated groove (whilst heated suction cutting is happening) and listen to the stereo turned up somewhat loud. Then add heat until the audible hiss from the stereo speakers drops considerably in level. Pull back the current to the setting to the knob deflection where this drop in hiss begins and leave it there (or move it a little lower, even, after 2/3 or so the way through a long side).

Bonne chance,
Serif

[opcode66]

The voltage is relatively irrelevant. It is the current that you are driving across the load (in this case the resistance of the nicr wire.)

The current and resistance combine to create heat in the nicr wire. 0.5 amps is the standard amount of current for all cutting systems I'm aware of.

[andybee]

Hi! thanks for your input!
The voltage is also important, because without voltage, no amperage,
very simple, and with a higher voltage there is less amperage needed
to get the same watts....
I will try the 12V with my powersupply...

If somebody has the circuit for the "commercial" styluses, like adamant or transco
please let me see
thanks again!

[opcode66]

What I was trying to say is that 0.5 Amps is the number you want to get at. Since V = I x R and I is the number we want to be 0.5, depening on the volts will vary depending on your load. I = V/R. You want I = 0.5 Amps.

[andybee]

one brandnew stylus killed. super!

[opcode66]

What?!?! How?

FYI, Neumann uses a 12V line for the stylus heat. I'm not sure about the schematic. I think I have it. I would have to look.

[opcode66]

Here are the relevant parts of the Neumann documentation.

[andybee]

yes, my fault, too much amperage...
12V with 0.5A is simply not possible directly at the stylus, it burns!
The Stylus has only 3.5 Ohm...
If I calibrate the amperage to maximum 0.45 ampere, the voltage
doesn´t move over 1.8Volt, and the stylus gets hot, if I touch it.
But it is a difference, if you cut with 33RPM or 45RPM outside or inside,
normally best thing would be a variable amperage.
I have also ordered the "famous" VMS DVD from ebay, it must be
included there, so I will see....

[andybee]

aaah, thanks!
as you can see, the 12V are NOT directly at the stylus, there is the regulating
resistor + amperemeter inbetween.
thanks, anyway

[opcode66]

Yes, precisely. The potentiometer is meant to trim the voltage going over the load. 0.5 amps at 12 volts with the trimmer in serial before the ammeter. That's it. There are no other resistors. Just the one pot acting as a trimmer. Both images that I put together are from the VMS DVD sold on eBay. I can't suggest it enough!!!!

[Nickou]

Andy

I check and check again and I have 12 volt and it is fine with 0.45 amp

and it si the same on all the 3 neumann lathe I can check and 2 of them are with with original heating power supply .

so there is a problem of metering somewhere ... here , but I don t beleive my multimeter is not right , or with your meter ...


to burn the styus I have give more current than 2 amp

[andybee]

Hi!

Thanks for all the input, yes, supplied voltage might be 12V, but at the
stylus there is only 1.5 or up to 2 Volts, more will cause more amperage -> overheating
of the coil.
The rest of the voltage is at the variable resistor 50 Ohm/10Watts or more.

The VMS 80 provides variable stylus heating, can be adjusted, let´s say
from 0.45 A outside to 0.75 A inside.
There is no difference between 45 and 33 RPM.

This is a nice feature!

[gold]

Hi!
The VMS 80 provides variable stylus heating, can be adjusted, let´s say
from 0.45 A outside to 0.75 A inside.
There is no difference between 45 and 33 RPM.

I have never heard of varying stylus heat from the outside diameter to the inside diameter. I always figured that if I adjusted the heat for lowest noise near the outside diameter then more heat would risk getting horns. No?

[andybee]

a VMS 80 customer told me that, maybe an optional upgrade?
but, this makes sense!

[Nickou]

Hi!
The VMS 80 provides variable stylus heating, can be adjusted, let´s say
from 0.45 A outside to 0.75 A inside.
There is no difference between 45 and 33 RPM.

I have never heard of varying stylus heat from the outside diameter to the inside diameter. I always figured that if I adjusted the heat for lowest noise near the outside diameter then more heat would risk getting horns. No?

No idea if it is a option, but the only VMS80 I worked with had this possibility.

For all the cut I do, I begin with 0.45 and finish with 0.65

To do get horns , you have to heat a lot more , more than 1,5 amp I think.

[boogievan]

Paul is right. The heat should be set by ear at the outside, and, if anything, the current should only be slightly reduced during the side (not increased), since the heat is building on its own through imperfect dissipation. Watch for horniness. If the heat was sufficient fully to be pulled during the starting spiral (often conflated with lead in, which is really one full revolution at base pitch after the starting spiral), it should be adequate for the packed grooves.

As for Amperes, one can actually keep the source voltage and load impedance the same yet get additional current by supplying a tripping voltage to the depletion zone of a mid-stream transconductance varistor.



- Tim E.