Re: [TCML] Terry Filter for OBIT's

["Paul Brodie" <pbbrodie@xxxxxxxxxxxxx>]

Good point Matt but you still didn't address the need for a filter with this 
type of transformer. I am assuming, from your other comment about using a 
Terry filter to Andrew, that you espouse the use a filter with all 
transformers???

In regard to the cost factor, I failed to mention that OBIT's are almost 
always available on eBay for about $20 plus $10 for shipping and this still 
makes replacement quite a bit less than the full cost of building a Terry 
Filter.

This leads to my next question. About 5 years ago, I had two previous TC's 
based upon neon sign transformers and out of ignorance never used anything 
but safety gaps and never used a filter at all. One was a 15kV 30mA TC and 
the other one was based on a 12kV 30mA neon sign transformer and both used 
multiple spark gaps with very conservative gapping. I didn't run my coils 
for long periods of time, usually not more than a few minutes at a time, and 
I never had a transformer failure. I have had several other types of small 
Tesla Coils but they were based on very small power supplies and I do not 
feel they are relevant to this discussion.

So, my question is whether you believe a filter is an absolute necessity 
with all but pole pigs or is it simply added insurance? Please note that I 
have no opinion or even a dog in this fight. I am just asking.
Paul
Think Positive

----- Original Message ----- 
From: <mddeming@xxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, January 02, 2010 9:09 PM
Subject: Re: [TCML] Terry Filter for OBIT's




I finally got in my "OBIT" and it isn't an OBIT at all. It also isn't 9000 
volts and 50mA. It is actually a power transformer built similar to a large 
MOT and is 6000 volts and 50mA. I'm pretty sure the 9000 volts was a typo. 
The guy I bought it from just would deliberately give the wrong information. 
It is also a very hefty, 21 lbs. The core measures about 4" by 4.5" by 6" 
and it is apparently wound with the primary underneath the secondary, as 
there are two wires that go from the primary binding posts to the center of 
the windings and the secondary binding posts are mounted on top of the 
windings. It is NOT wound like most MOT's I've seen with the primary and 
secondary windings separate. The secondary is also center tapped.

Since I now have very little to go by about how substantial this transformer 
is, I think it may be wise to simply go ahead and use a filter but since I 
only paid $20 for it, I'm having difficulty justifying the expense to do so. 
Maybe I should just use a safety gap?

The justification for a Terry filter is not what you paid for your 
transformer, but rather the cost you will have to replace that transformer
with another if and when it fries. If you won a car on a $1 raffle ticket 
would you not put good brakes on it because they cost more than you paid for 
the car?

Matt D.


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