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Help needed with old coil circuit

Original poster: peterB <zardoz@xxxxxxxxxx>


I am in the process of restoring an old twin coil portable x ray
apparatus made by Wappler.

It has a strange circuit which doesn't make sense to me (keep in mind I
have limited knowledge of circuits to begin with), but I have seen a
number of old circuits (and new) that are close to this, but this one is

First, I have been in contact with one person who recognized the circuit
but thought perhaps it was wired wrong at the factory (unless it was
tampered with later, though it looks original) (supposed to have worked
as wired though, I was told)

The schematic and wiring diagram I drew from the machine is at:

NOTE: the schematic and diagram of how it is currently wired appears
just below the first two diagrams. The top two diagrams are based on
what this person thought I should change in the circuit.

The actual device (I am documenting its restoration) can be seen at:

(4 pages, although, the general idea of the actual machine can be seen
in the black and white photo on the above page.)

My questions: (refer to the two drawings below the revised drawings)
The primary of the transformer is connected to the secondary. This I was
told was a relatively common practice.

I quote Frank:
"2) The secondary connected to the primary is also a common wiring
this way the components do not need so much insulation. Also, the
transformer is a high current, low voltage type. Probably a max of 2KV
it is easy to tell this by the standard house wire on the secondary.
Not to fear tho, the current is what makes the coils sing!"
He suggested I switch the wires going to the primary, (see photo towards
the bottom of the schematic page) These are the two wires that terminate
at 'a' (spark gap) and 'b' (ac in). This change would result in the
schematic at the top of the schematic page (and the new wiring diagram
just below it.)

Some other info Frank passed along:
"3) As you probably guessed, with the secondary circuits connected to
side of the 110, the shock hazard is very great if you are grounded,
with the set off!

4) The cautery circuit is a true RF type, with the jumper removed, the
circuit is a cap in series with the HV and you get a nice fat arc.

6) The Tesla circuit is with the cap(s) in series with the transformer
the spark gap is in parallel across the transformer output so it is very

important NOT to ever close the gap completely as it will short out the
transformer and pop the fuse.

Now, the way you drew the circuit, the secondary is in series with the
primary and this will not work. I think you will find the RH side of the

gap connects to the common pri/sec side of the transformer and the
switch does not go to the gap. The set cannot work as drawn without
the transformer."

The resulting arrangement shown by the schematic at the top looks like
it would lead to HF leaking into the AC lines, as there is no choke.

My question, if the re-arrangement of wires as Frank suggests is
correct, will there be a danger of HF leaking into the AC lines?

NOTE Diagrams: when the multi position switch is set to 1, 2, 3, or 4, I
could see the voltage regulation coil acting as a choke, but at position
5, which by-passes this coil, there is no choke. Could the strange
wiring as shown in the original schematic and diagram be wired that way
so the transformer would act as a choke? Is it even possible to operate
this apparatus without making the change Frank suggests, or should I
switch the wires and add a choke (if a choke is necessary)?