Paint Job

After some back breaking working with steel, All the steel (at least what I know is requires) are cut, drilled, taped, ground, de-burred and painted.

This is the hardest part of the whole build as I have to lift serious weight, endure flying sparks, deafening power tools noise, work in dust filled environment, work on my knees, squatting for long hours & drinking 3 litter of water each day for over 2 weeks...

My advise, get a helper....

The dust is intensive, I lost count after I swept up two 50 liter buckets of grind steel dust...

I then decided to paint the steel before welding to avoid the intensive Yoga exercise session if I were to paint the table after the table is completely welded... Can always repair the scratches & welding burnt paint with a tat to extra paint...

Painting is a PITA task, easy to do but takes ages to reach a competent level of finishing...

How much PITA? Before you paint, one has to prepare the steel...

• Firstly, you have to remove loose scale & rust with grade A60 sand paper or power brush with an angle grinder, 
• Secondly, you have to rub down the dust & any oil stain from the surface with solvent, I use patrol for this task as they are great solvent that are easily available & they will evaporate without a trace. There are other practices such as wahing the steel with light detergent but I alway prefer how I did it...

• Then you get to paint...

Now, you can op for spray painting or hand painting... as my body is all sore after the earlier works, I hate to haul all the steel into the open & haul them back to the workshop after they are done... AND its raining season... a bad bad thing for wet or half dried paint...

*ps, It did rain a few time (per day) during the 3 day span of my paint job.

I use 4" paint roller for the job, some how, I can't paint with normal paint brush & roller saves me from the emberresment. AND with rollers, it is easy to control paint thickness & produce a even matted finishing which I like.

My paint selection :- 1 coat of Red Oxide primer & 2 coat of Enemal Alkyd paint (commonly know as Glossy paint).

More painting PITA....

1. Apply the 1st primer coat after the patrol had evaporated & squeaky clean...
2. Wait...... 4~6 hours for the primer to cure enough for the top coat... Too short the curing then the primer will be too wet for the top coat, too long the primer will harden too much for the top coat to "bite" on to the primer coat...
3. Apply the 1st coat, do not brush over the same spot over & over again, this will make the top coat to mix with the primer coat... Nevermind if you can still see the tint colour of the primer coat on this 1st top coat, you can get this corrected with the 2nd coat.
4. Wait..... read the instruction on the paint can, it says 4 hour for touch dry & 6~8 hour to re coat.... I waited 8 hours & they still feel too tacky for the second coat so I left them over night to cure properly...
5. The 2nd coat will be a breeze as you had already 2 coat of practice & finish in no time.

This is what I got

 The laser cut profiles.

The table parts including the rails in black

The table bearer channels 1 1/2 x 3" channels

Close up of the main 3" x 8" channel

The table leg & supporting tube trusses

Not forgetting the rails, with 2 coat of smooth black Hammerite paint...

Arduino

It has been a few years since I’d started to look for a mean to start on micro controllers stuff. PIC is the recommended chips as I was told they are cheap and abondon locally.

Bought many books and spent hundreds of hours surfing the net with no fruitful progress…. These books eventually became my best cure for insomnia… It never fail to put me to sleep in 20 minutes…

Everything which I found require me to build some thing, either a programmer or hardware to actually make the micro chip work… Its too much challenge for me… so the search continue

Found this book while wondering aimlessly in my local book store a month ago.

By Massimo Banzi, co-founder of the Arduino Project. Published by Make Magazine.

The cover cough my eye.

“Arduino” has appeared with increase frequency in my google search for how-to starter packages for electronically challenged beginner like me. I didn’t dig this AVR based board as I was looking for PIC stuff. What a mistake!

This is the only book on MCU which I finish reading in one go… and awake!

I learn what Physical Computing meant, Arduino uses C language, everything is open source, the board contain the necessary hardware to operate and plugin USB.

Arduino is “ready-to-go”, no need to know about bootloading, I/O connections, I2C, USB chip, communication chip... etc etc which I couldn't care less, so that noobies like me can get our claws right into the fun part.

There is a growing community such as
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl
Seriously fun ppl.

and their web page is packed with great stuff such as ready made codes/programs, meaning we don't have to reinvent the wheel!
http://www.arduino.cc

The potential application is only limited by your imagination! We can do useless thing with it such as teaching our flower to call for help when they get thirsty, lights off in the absent of occupant, control an autonomous robot, intelligent home system, track the sun, control an miniature UAV, feed the monkey, skin the fish.... all of which you can jump straight in as long as you know what make things tick, perfect toy for tinkerers.

Just placed an ordered a "clone" Arduido starter pack, (wanted to go for the real thing but they have the best shipping charges.) should arrive by next week, can't wait to blink some LED....

Tube Curves is Your Friend

Common stereotype misconceptions that tube design is for tube gurus with in-depth tube knowledge, Master Yoda-ish character and is one-with-the-force; In reality, anyone who is competent in prevent/avoid electrocution while working with high voltage and still remembers Ohm’s Law is competent enough. All you need is the data sheet. Allow me to demonstrate.

Firstly we get hold of the 6DJ8 data sheet as follows:-







You can start by determine the max and min safe work condition, gain, Rp, rp, plotting the best loadline… etc.

BUT I WON'T!! I will reserve that for your self-amusement during your dreary hours…

Use the Data Sheets recommendations and get straight to it before the irrational impulse of building a tube preamp subsides.

From the #Page 1 of the Data Sheet we have
Filament voltage, Vf = 6.3V,
Filament Current, If = 365mA
From this, we calculate the power required by th filament Pf = Vf x If = 2.3W

#Now write down this on your shopping list, “ 6V, >2x365mA (1A is common),transformer”

At the end of #page 2, "maximum rating, absolute value"
Series grid Resistor = 1 megohm max

you will find "Typical Charateristics" and the followings

Plate Voltage, Vp = 90V, This is the voltage across the anode and cathode
negative grid voltage, Vg = 1.3V, this is be the Bias Voltage
Plate Current, Ip = 15mA, with triode, Ip= Ik, cathode current

Now some maths,

Find Rk, using Ohm's Law,

V=IR
R=V/I
Rk = Vbias/Ik = 1.3/0.015 =87 ohm #

Determine B+,
We will use Isolation Transformer, In my part of the world, main power is 230V AC,
Using Isolation Transformer with a bridge will yield,

Raw B+= Sqrt(2) x 230 = 325V,
we will filter raw B+ to 300V

VLoad = 300V - Vp - Vbias = 300V - 90V - 1.3V = 208.7V #

RLoad = VLoad/Ip = 208.7V/15mA = 13,913 ohm we can choose 15K resistor.

Well after all this hard work, I need to get my regular coffee fix.... We'll continue on the next installment

How to Sound Like Tube Guru 101

How to Sound Like Tube Guru 101

Common Cathode CC is name as such because its Cathode is connected to the Common Ground.

The CC is good at Voltage amplification, i.e., magnify signal; this is generally the strength of glassware.

It has high input impedance of easily a few hundred thousand ohms; in plain English, it is very sensitive to input signals and very easy to drive.

Fairly high output impedance, which means it is not so good at driving difficult or less sensitive loads such as Solid State Amplifiers and Loudspeakers without some neat tricks but its sufficient to drive another tube stage.

Biasing, to get the tube into operating condition, we set the DC bias or quasient state, its like getting your car on idle speed; When AC signal (yes, signal can only be AC, that includes noise signal too) is applied, its like stepping on the accelerator, and the engine will respond accordingly to how hard you step on it

There are 2 biasing methods in general, Fixed-Bias and Self-Biasing. My emphasis will be on Self Biasing as IMHO they are easier to tinker with and better sounding too.

Self Biasing means we put something (resistor, LED, Diode, Battery or Constant Current Sink) between the tube’s cathode and the ground so that it can generate the required bias voltage by themselves, hence Self Biasing.

Input signal, lets consider CD player output signal of 1Vrms, that means 2.83V peak to peak. V max of +/-1.414V.

You don’t need an input capacitor solder in your circuit as CDP already has an output cap to do the job.

Output coupling. We are going to use Capacitor coupling. This capacitor will ensure only signal voltage is delivered to the next stage. That’s all you have to know for now.

Recite the above to your pal is enough to impress your tube ignorant buddies.

Common Cathode Amplifier

Common Cathode Amplifier

Glass-tech is over a century old…. How hard can it be????

To cut short the chase, we will pay exclusively attention to triode for now. This should spare us from pages upon pages of boring tech-loaded content. Jumping straight to Common Cathode Amplifier (CC from here on), will speed up the whole process even further.

There are more then ample articles written on the basis theory in the net, spend some effort to google will reap fruitful return. I'll leave this to the readers to decide.

CC has its strength and weaknesses, but hey, it constitute vast majority of audio circuit in its plain or modified form, that speaks strength for itself.

Tinkering 6DJ8

6DJ8 is the tube of choice, small signal triode, with 2 triode encased in one glass envelope.

It has a large family which is fully compatible, namely,6922, 6N1P,6N11, ECC88, EC88C, E88CC, E188CC, E288CC, .

Plenty of tube rolling opportunity.




It is good sounding, wide applications. It's high Gm, medium gain and low Plate Resistance. With some circuit tinkering, we can build quality Pre-amp, Buffer-amp, driver for small power SE amp, headphone amp... etc

IMHO the only tube which will sound normal when connected as cascode.

There are plenty of NOS (New Old Stock) available, as well as current production.

Circuit Theory for Tinkerers

Like it or not, we need some basic Circuit Theory for tinkering in electrical and electronics gadgets.

BTW, changing a plug, replacing a wire, spay some paint does not count as tinkering in my book. When I tinker, I dig deep.

Where did I picked up the circuit theory know-how?

All Engineers took electrical classes somewhere along the academic route; We enter the classroom, went through the motion of listening to the teach/lecturer, collect all the handouts, do some tutorials and off we go to the exams… to return the knowledge in written form. Hopefully, some of these knowledge will residual in our brain. In my case, Ohms Law, power and summation of component value calculation stayed….

Lucky me, enough for tinkering and be dangerous.


Ohms Law

V = I · R

V is for voltage, V is the unitI
I is for current Ampere, A is the unit
R is for Resistance, Ω ohm us the unit.

From here, we can derive the following equations

I = V / R

R= V / I

Power

P = V · I

Where,
P for Power or Watt, W is the unit
V for Voltage across the component
I for current running through the component

Summation of Resistance

Series Connected Resistor,

R_total in series = R₁ + R₂ + R₃ + … + R_n

Where,
R_total is the resulted total Resistance of the series connected resistors
R₁, R₂….Rn are the Resistance of individual resistor

~handy tips,

When connecting same value resistor in series,

Use This --> R_total = R_individual x Pieces of resistors

Parallel connected Resistor,

R_total = ((R₁)^-1 + (R₂)^-1 + (R₃)^-1 + …. + (R_n)^-1)^-1

Where,

R_total is the resulted total Resistance of the connected resistors

R₁, R₂….Rn are the Resistance of individual resistor

~handy tips

When connecting identical value Resistor in parrallell

R_total = R₁ / pieces of resistor

How to use them?

• Ohm’s Law enable us to figure out how much voltage is across the component and how much current going through the component.

• We use this as the minimum required ratings, i.e. current, voltage and watt rating of the components. *PS* For Power rating, give it at least a double,I triple when I have the chance.

• Summation of resistor allow us to add/reduce R_total in the circuit. By changing the R_total, when use with Ohm’s Law, we can figure out how to adjust the current and voltage of the circuit and/or components. Which is an essential know-how for tinkering.