Hi there!
Point 1:
Can certainly do this, there are also additional resistors in the charging brick, there are some pictures on my blog but i will draw out a schematic for you. The charging circuit is very simple, just the transformer, rectifier and current limiting resistors. I am interested to know how often the transformer is switched on as it is switched by two SSRs.
I am away until tomorrow so will follow up when i get a chance
Hi again Dexter.
It would be great that you could create a schematic for it.
I have just used tinycad (downloadable here
http://sourceforge.net/projects/tinycad/) to create a brief sketch of what I understood of the circuit so far based on your videos.
I'm attaching the schematic file in case you want to edit your findings there.
In particular, I would like to have learn more information on the following aspects, in descending order of importance:
1) Grounding of the device.
Is the device connected to mains earth? If so, to which components does the ground line exactly connect inside the device? Only to the box chassis (in case it has a metallic chassis inside?). I am currently assuming that the ground line does not connect to either the transformer and the capacitor, (Kindly check this), as I'm guessing the secondary of transformer and all connected components should be floating, to avoid accidental closed loop through the patient.
2) The relative placement of the series diodes and the SCRs.
In my tentative schematic, I have placed them how I would expect them to be theoretically, but I'm not sure if this is correct or not. I have placed the diodes in anti-parallel with the SCRs as their function would be to conduct on the negative cycle of the LC tank, i.e, while the magnetic field collapses. (I have attached a drawing I made to describe the 4 quadrants on a LC tank). According to the specs of Magstim 200 the pulse is monophasic which would mean that the diodes would conduct on the second quadrant, reversing the voltage of the capacitor.
Theoretically it would make no sense to interrupt the current at the end of quadrant 1, considering the law of continuity of the magnetic field (guess it's related with Gauss' Integral Law of Magnetic Flux), so I assume the 2 IXYS diodes are actually placed to conduct the reversing current while the field collapses and not to block it. Kindly check how this is actually connected to confirm or refute this, reflecting any necessary corrections in the schematic. (checking the discharge current in the scope through your current transformer should shine a light on this too)
I believe Ben Krasnow used diodes in anti-parallel in his experiment, although I was never able to understand from his scope readings how exactly the current was extinguished.
Maybe in Magstim 200 they simply cut out the magnetic field while it's at its maximum, without allowing it to collapse? (Now my big doubt here: could a magnetic field on a coil be extinguished without letting a reverse current to be established? This is currently a paradox to me)
3) The charging module.
If possible, try to replace the charging module (the black box) in my schematic with the elements you found inside and the connections between them.
You mention a rectifier in the charging circuit. Is that rectifier inside the charging module or is it apart not shown in your videos? I got very curious too on how that charging module is working as seems to be the tricky part (wondering if they have a patent on this part of PSU) You mention the SSRs are switching the transformer, so if that's the case, my tentative schematic will have to be quite modified. Please mess up with it as needed.
4) The trigger module.
This is the less important, but I'm guessing if they use pulse/isolation transformers there or other components (like opto coupler maybe? too sophisticated for a 90s machine maybe?), am wondering if it has other functions there, like reading the capacitor charge level, or other functions, but if you can figure out the connections and the components types (assuming that you won't be probably able to retrieve most of their values), would be a nice to have.
Sorry if I'm giving you too much work. Thanks so much for your help.