oneTesla

A couple of observations from someone who does PCB repair for a living:

In the assembly instructions pertaining to mounting the two fibre-optic connectors, it seems to suggest that you solder them first and then nut-and-bolt them to the board. It's normally done the other way around, because unless you've got the component perfectly in contact with the board when you solder it, you'll stress the solder joints and PCB tracks when you do the nut and bolt up. I would always nut-and-bolt it first, and then solder the legs to the board.

The big heatsink isn't (it appears) mechanically secured to the board, relying instead on the legs of the transistors to keep it in place. Over time, vibrations from operating the tesla coil are likely to cause the solder joints to crack. Additionally it's vulnerable to damage in transit once the board's assembled.

Looks good otherwise - I'm eagerly awaiting delivery of my kit. We'll see how much trouble I get into when I take it into work....


Paul

The fiber optic receiver and transmitter have some play between the legs and the case, it should be fine. For a while I didn't even have a nut and bolt on there

The heatsink is right up against the board and the bus capacitors, and the IGBT legs are thick enough that it isn't a problem.

Good luck with your build!

paulm1234,

Bolting down the fiber optic connectors before soldering them to prevent straining the device is a good suggestion. There is some slop in the case and the leads which makes it usually OK to solder and then bolt down, but it's better practice to do what you say.

Regarding the heatsink, it's secured this way in order to make servicing easier. You're probably going to want to replace the bridge at some point, and just desoldering the IGBTs to do so makes it easy.

On a simialr note ,your instructions say to trim the leads after making the join , which will put stress on the join

I just read all through the manual and it seems the most glaring error is the lack of a schematic and parts placement diagram. How the heck are we supposed to understand how this thing works without a schematic? Pictures are nice, but the top view of the main board on page 27 (rev 1.33) does not help you verify correct parts placement after they are installed.

Also the gate drive transformer instruction page needs a schematic representation of the toroid transformer indicating phasing. My kit came with pre-twisted wire which is a nice touch, but there were 4 (FOUR!) wires which really threw me off. I had not wound a toroid transformer before and would have appreciated a bit more in the way of a tutorial on the design and theory.

The full schematic is on the web page. Click "downloads" and it's right there. I agree that a full schematic would have been nice in the manual as well, but at least it's available.

The component placement is very clearly printed on the board, with component numbers and values, but yes, I would have appreciated a printed 1:1 scale version in the manual as well. The Eagle files on the web page are of no use to me, because I lack the proper software to read them. I think a PDF version of the PCB layout would be a good addition to the "downloads" section.

After having some discussions with Bayley on performance problems, I would suggest that you add some more detailed instructions in the manual on how to properly solder the IGBTs on both sides of the board. It is good advice to tell people not to rely on the through plating to carry the large peak currents through the C and E connections for the IGBTs. In another forum thread (the thread that exploded, I fear it is done for), he suggested soldering the C and E pins on the upper rail IGBT and the C pin on the lower rail IGBT also on the top side. I see no mention of this in the manual. If soldering with through plating works the way it should, solder should flow through the hole to the front and connect with the pad and the pin on both sides of the board, but because of the high thermal conductivity of the IGBT traces, this did not happen for me. Also, when desoldering the IGBTs, the through plating often gets damaged or drops out of the hole completely.

Soldering on the front side of the board is a bit tricky, but the order of assembly I would recommend is this:

Do not mount the GDT before the IGBTs. It gets in the way.
Attach the IGBTs to the heatsink, but do not use the sil-pads and the thermal paste just yet.
Solder the IGBTs on the back of the board.
Remove the heatsink from the IGBTs to have some more room.
Solder the IGBTs on the top side.
Reattach the heatsink, using sil-pads and applying thermal paste.
Last, mount the GDT.