Good advices for a newbie (threading tools lathe)

[PJs]

Thanks for the update Stefano. The 813 is a great tube for this I think, very robust and will handle what you have to give it. Many years ago I had a matched pair of RCA 833's with gold grids I used on a transmitter...that's what the HV power supply was for. Later I traded them for a Diamond Back bicycle for my son. Wish I still had them as the prices for them now are through the roof. The Gu81 is similar only a pentode. The 12au7 is one of the all time great audio tubes in my book...Think you will be fine with that.

Nice size tesla coil your friend built! Way fun!

Look forward to your next update. ~PJ

[rendoman]

Hi, small update
I buyed this cheap frequency counter on march 20 (something about 13 euro) , just arrived few hours ago. Very poor packaging, damn chinese seller, poor quality shipping with no tracking number, but al least after 2 months is here. 9v dc supply, I have to make an enclosure for this double pcb circuit. I made a speedy test with the last known coil, tested one month ago with a professional frequency counter Hp (some ghz), I remember the same value one digit after decimal point, that's pretty good for my purpose, I'm happy to have the unit value. For sure there are some powerful mitigations inside the circuit, number are too much stable compared to Hp unit.
In few words: for 13 euro it's a good instrument, it's rated for 0,5ghz and it seems that it works good. I will make a little enclosure to preserve it from damage

[rendoman]

hi! new little update, not for plasma
I buyed today 2 oscilloscope, the first is a tek with calibration certificate (fresh of one month) and the second an old unaohm. Both pretty good, with probes.
Now I have to study a little how to do measure with high current and voltage circuit, then with rf circuit
Hope I will not burn the scopes

[PJs]

Very cool Stefano! Glad you went this route as these will be invaluable I think, compared to your frequency counter...although handy. They will give you the advantage of measuring and checking signal quality throughout your system. These are great choices for what you are doing. Is that older one a Unaohm too? Reminds me of my old Eico but has an HP/Tek look to the case of that era.

I have an old TEK 2645 4ch analog that was used in a University lab (regular calibration) and almost new that I use for analog audio work. Also have a TDS 320 for digital work...both great and you will get used to the Menu system with a bit of practice. I also have a BK 4017B generator that works great for my general needs plus the 4 channel HP8409a I put in the Hawk - DC-600Khz.

Check your probes for quality and any issues with noise...And Definitely ground your probes...You'll be fine! Great find and new additions to your tool box!

Thanks, ~PJ

[rendoman]

Hi all!
Thanks to a friend who gave me the 813 tube, I will try a new plasma "on steroids". I got some troubles with current circuit, first of all I think I need brutal power from amplifier. I don't know how commercial (or free schematic) plasma runs with bu208a or small pentode, my prototype with such power doesn't do even coffee ! I'm thinking about rebuilding a module with amplifier and modulator ( I think el84 ) and trying both gu50 and 813. Currently flame is good enough, maybe needs a little more driving capability.
I'm thinking about use another gu50 as amp, maybe with an ECC family tube. I need to build a good outuput transformer, maybe 5k from 20 to 20k or a "special unit" anode choke up to 200hz ( 1\5 turns ). I got some different voltages from powersupply, excluding 1100/1200 v I can make dc from 250 to 600v, I have to choose a good load and working point for gu50.
I tried also tek scope (not connected to circuit, frequency counter with plasma on, i post some pictures

[rendoman]

Hi! New update
I tried my new Rca audio generator (nos) with plasma circuit, in order to drive it at full power.
Things are better! more volume, sound starts from 100 hz. Making this test is annoying, it's better wear ear protection next time
At least now is sure that I have to change both audio amplifier and double (or change) oscillator tube in order to gain more volume and avoid destroying the tube

[rendoman]

Hi
Better quality of sound, video and new pictures!

Audio generator drives plasma at full power, Volume is pretty good now, but I want more
It's funny to see how flame can change of shape and size with volume and frequency. With very low freq you can see the flame is open with multi point, higher the frequency flame becomes sharp like a candle.
I'm drawing a new circuit with el34 and 6sn7, both octal socket, tight and strong.

[Toolmaker51]

Rendoman;
Guess I haven't looked at this post. Nice shop buddy!
I don't recognize what brand of lathe you have. I know/ used Cazenueve, Nardini, HES, TOS, Rambaudi and Graziano. That quick change toolpost is what I use. Those widely spaced vee's can really take the power. I associate them of Italian and Swiss design, hard to find here. They aren't impossible to duplicate, that is on the list. They might have been introduced by Enco when they imported good tools [ when no one cared where China even was]. I'll find something I can send on tool grinding. Good choice on convertible mill too. Vertical might be preferred simple setup thing, but horizontal is REAL milling! Is it 40 or 50 taper? You have multi-collet tool holders and rigid holders too?
Photo 6 tells me 'troncatrice a disco lento' is a 'cold saw' = coolant/ hollow ground blade and straight teeth/ swiveling vise [almost a milling vise] and direct drive.
That's a super blacksmith's post vise too. If you're only going to have one vise, then make it a post vise! Flat shear, bender, welders...When Jon asked what your next project was, you could say "Anything I want".

[rendoman]

Thank you very much!
it's from few years that I collect old equipment, for two reasons: the first is the low price, and the second is that here in Italy is almost impossible to find a not chinese tool running with home main voltage. Industrial type 380v 3 phases are really expensive. Old shops throw old equipment, with a bit of fortune is possible to find good pieces, I need only patience

My lathe unluckily lacks of the label, I searched in every part but not a name impressed on cast iron. It should be an old " Grazioli Fortuna 150 model " . Base,head and legs are from old type leather external belt but transmission is internal with triple trapezoidal belt and 3 gears. I maybe be wrong, but It can be a lathe of a transition period, maybe 50\60. I Had for very low price from a friend, but I restored many parts like gear bearings, rebuild a shaft of internal auto transmission and other things. Luckily old owner changed some months ago big bronze bushings. 3hp- 2.2kw 3phases engine with 120uf capacitor, run very good with normal 230v monophase voltage, never run hot, even after long use.

Milling machine is a old type Cst, factory is still alive, it is maybe 25km from my town. Morse 2 taper unfortunately, but it's old. I got vertical head and horizontal shaft with spacers and some tools, but I use really a little this. I got a multi collet, er25 if I remember correctly, and a couple of 20mm mills with 2morse taper fixed, imho better to use.

Thanks for the name "cold saw", it was difficult to find the correct name of this machines.
I'm thinking about making a portable table with post vise, grinders and welders, useful to do things in different parts of house, free some space in my poor little garage and provide some tool support inside. I remember the day I buyed my first ac welder, owner told me to see if there was something else I desire, for 5 bucks I buyed the post vise! good times!

My biggest problem is that I need more skills, I'm only an amateur self-taught that try to make things, sometimes good , sometimes bad... like Yesterday, when i do a bad move and I crushed my finger It appeared a face of my nail! Hope in few days to have less pain

[PJs]

Hi Stefano, Great job getting this dialed in. Personally I think you are there with the power and the 813 (Great old Tube) will be overkill (400W) and may cause some issues with your plasma electrode design and your Horn to handle it. Also keep in mind, your horn will amplify and directionalize the sound you already have...and You already need ear protection.

Glad you got a frequency generator too...Is it an old Tube Type? It's the only way to really look at the input versus output. 18-20k is pretty impressive but noticed you may have been running it on Square wave not Sine??

I watched the videos a couple of times and not quite sure what to say about the differential flame shape. My gut is telling me it is a distortion at specific frequencies or maybe some type of harmonic resonance/dissonance.

My thoughts at this point are: When I built the Hawk and was testing the transducers I used a program called TrueRTA (Real Time Audio Spectrum Analyzer). It's about $100 for the 24 octave version and used it with the ECM800 mic and a 48khz sample rate, phantom power, mic amp. Newer amps are good to 96khz+ sampling. The software has a built in 2 channel scope but what I wanted was the Data in spreadsheet form. Basically I output from the software, 24 octaves by frequency and Db to look at the harmonics and what the real frequency range was based on the Db output...plus the scope has a capture feature. To drive the transducer (your plasma) I used the HP8409a in sine mode with a 4-5 second sweep from about 8-35khz...you can do this by hand with your FG and just sort the data a little finer in the spreadsheet. What this will give you is as true a picture of your input to output (by frequency/Db and harmonics) as is doable without a lab and high end gear. Distortion can be looked at using the scope in the software but it needs to be at specific frequencies, like when you flame splits or within the range you want your "Flame" system to run at.

Another thing to keep in mind with the ECM8000 mic is the distance from the flame but also to shield it from any 50-60hz hum from the other equipment or extraneous room noise. I used a 2m mic cable to keep it away from everything else and on a mic stand to isolate it more. I might also consider putting your glass tube housing on if that is where you are going with it....good time to test that too.

I am super impressed how far you have come and what you have accomplished on this project and can't wait you see you box it up for use!!! Thanks for sharing all of this with us.

~PJ