Re: tesla coil does not work...

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Qndre Qndre" <qndre_encrypt@xxxxxxxxxxx>

Hey.

Let's check your circuit step by step. Since this 
issue can be caused by almost anything we'll 
check each and every single component till we get 
the one which is not functional. This can be much 
of work but since the issue seems to be pretty 
hard to locate, I don't see any alternative to this method.

1. Wiring: If it's a center-tapped secondary with 
the center tap connected to RF-ground (NO 
connection to mains-ground!!), midpoint-grounded 
like you said, you can NOT ground one end of the 
secondary as well as this will short out half of 
your secondary winding. Do not ground any of the 
hot wires but only the center tap which will give 
you two hot wires, each having 5 kiloVolts in 
reference to ground being 180° out of phase, 
having 10 kiloVolts between both hot wires. Now 
connect these two hot wires to the main spark gap 
(with a Terry-Filter in between if you want to 
protect your mains transformer from the RF). Now 
wire primary coil and primary capacitor in series 
forming the LC-circuit which should then be wired in parallel to the spark gap.

2. Mains transformer: You should be able to get 
an arc between two pieces of wire connected to 
the high-voltage output if distance is close 
enough. If you get an arc, we're going to check the next component.

3. RF filter / NST protection / etc.: Hook up 
your protection circuits to your transformer but 
nothing else. Power it up and see if they have 
internal shorts etc. which will make your 
transformer hum or the faulty component burn. ;)

4. Spark gap: This should not be conducting 
unless it's firing voltage is reached. Hook the 
spark gap up to a low-voltage power-supply. You 
should not have any current flowing through it. 
If current flows, you have an internal shorting 
(electrodes touching each other) or a carbonized 
path somewhere. If it looks OK at low voltages, 
hook it up to your mains transformer together 
with your current-limiting. The voltage should be 
high enough to make it fire. If not you have to 
reduce the distance between the electrodes. If it 
fires we're going to check the next component.

5. Capacitor: If using an MMC you can try to 
charge every single cap using low-voltage DC and 
measure it's voltage to see if it holds it. Don't 
forget to discharge every cap after this since 
you have many caps in series in your MMC so you 
can get hazardous voltages across the whole 
circuit since the voltages of all the caps in 
series will sum up. Also remember that caps can 
regain charge from dielectric memory. If all the 
caps hold the charge properly we're going to 
check the next component. This measurement can be 
a bit harder if you have bleeder resistors across your caps.

6. Primary coil: This should be rather 
conductive. If it isn't, there's something wrong with it.

7. Secondary circuit: If you still don't get any 
output, there's something wrong with the tuning, 
the coupling, the secondary is broken somehow or 
doesn't have a good connection to RF-ground and 
the topload capacitor. Check your secondary 
circuit. If you are absolutely not sure if you 
manage to achieve resonance between primary and 
secondary circuit you can try to measure the 
resonant frequencies of both using a frequency 
generator and an oscilloscope. The coupling is 
usually increased until you get racing arcs, then 
it's decreased a bit to achieve "perfect" coupling.

Regards, Q.

----Original Message Follows----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: tesla coil does not work...
Date: Thu, 12 Jan 2006 19:35:57 -0700


Original poster: "Langer Giv'r" <transworldsnowboarding19@xxxxxxxxxxx>

its a double pole xfrm with mid point ground 
connected to the ground on my safety gap, and the 
two hot wires are connected in series with the LC 
ciruit, and in paralell with the main spark gap