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[TCML] Re: Finally finalizing my 304er VTTC

Very nice setup there Chris! One of these days I'll have to post my GU-81M VTTC too. I've been having some trouble getting my staccato controller to work so I should probably think about getting back to troubleshooting that thing.
Thanks for the inspiration!
Matt Lewis, Fairlee VT

-----Original Message-----
From: Chris Reeland <chrisreeland@xxxxxxxxx>
To: tcml@xxxxxxxxxxxxxxx
Sent: Fri, Apr 23, 2021 10:26 pm
Subject: [TCML] Finally finalizing my 304er VTTC

Hi all,

Fairly recently, I have decided it is finally time to get this finalized,
inspired by others here :^) and will share this. This project will take
some time and will update as I go. This is a single tube Eimac 304 and a
single MOT with a level shifter with 120V input from a variac. This has
been a great running little fella.

Some goals also so far are:

- To have this completely and very easily portable and light as possible.
- Very simple setup, just a single plug to any 120V outlet, to power
everything. One slight exception is the accessory 120V cord plug coming out
the unit to power my several different kinds of interrupters I have and the
"trigger" wire connector from the interrupters. I do not want to be limited
to one type built in.
- To have this coil be as high performance as possible, but very reasonable
power draw. VTTC's can be horribly inefficient vs. arc length output.
- To take advantage of the heatsinking capabilities of the whole aluminum
enclosure and use a single fan to help take this heat away cooling stuff on
the way out. I want to be able to do VERY extended run times, with
everything staying "happy".
- To take advantage of some of the shielding this enclosure should provide.
It will be at ground potential. Everything thing iron/steel will be inside.
This will also greatly simplify several connections.
- And of course, look great hopefully!
- Still thinking of others :^)

I will admit that I am torn some here on an enclosure, I normally prefer
everything out in the open at times, but the advantages that I want
outweigh the "open". I am planning to make sure that I can get the top
cover off with the minimum of hassle to show off "under the hood".

Here is a link below to some pictures of it's current state after a quick
run testing it before starting to taking it all apart and the new aluminum
enclosure nearby.
Also a video taken oh... about a month ago...I did not take any video
today, but nothing has changed, so this is how it runs with one of my
interrupters now. Yardstick hanging in back as a reference.

There are going to be some changes here also... this is not a direct
transfer of everything...so the hope is not to have less performance!
I will try not to mess things up with some ideals I have.

And well, this is also a repair project, as the secondary is slightly
damaged for quite some time now. Down in the primary area the windings are
buckled some. Got over heated some, during some extreme testing I did. The
acrylic is now warped some. The epoxy coating can only do so much...
Kind of bummed to retire the coil form...been in use since about the early
to mid 1980's. For those that don't know, this VTTC has changed quite a bit
over the years especially the last 3-4 years from it's origins in the 80's.
Several different tubes, transformers, variacs, capacitors, secondary
rewound several times, primaries, etc. Somewhat surprised the secondary
works pretty good still with damage, even if though not really much voltage
in the windings here.
I will take some close up pictures when fully apart.


Oh...this is all I can think of currently...and I will think of more as I
go and post. There will be some tests along the way and I will also give
some numbers and specs.

Oh...a few numbers to start, the new/old surplus enclosure I found is
17"x17"x6". The old platform board is 20"x20". (Actually, this platform
board is the second one for this coil. Original much smaller, ran out of
room with changes. It has a lot of "bullet holes" as does this current
board from several changes experimenting as seen in one picture of the

Make some Sparkys all if you can :^)

Chris Reeland
Ladd Illinois USA

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