PCB Sneak Peek

[ErikN]

Hi Everyone,

We've been working on designing a circuit board to make assembling the standard SG circuit easier. I spoke with John B about this about a week ago and he asked me to post some pictures of the prototype board(s). I tested these boards this weekend and tonight and they work well. It's easy to find the sweet spot with the potentiometer, measure it's value and use a fixed resistor(the switch selects the pot or the fixed resistor). The orange jumper in the photos is where a light bulb should be placed. You'll also see I originally placed a fuse in the circuit, however it will not be recommended because it introduces unnecessary losses into the circuit.

Keep in mind, this is a prototype board and is subject to change; the actual boards will be silk screened to aid in component placement.

Erik

[Woody]

Nice!! I will be purchasing!!

-Woody

[Howard Wetsman]

Erik,
I like it a lot. Thanks for doing this. I really like that we wouldn't have to solder the power wires of the coil or the battery connections. I have a few questions.
Are there sockets for transistors the way there are for ICs? Blowing transistors has been a common occurrence and sometimes the traces come away from the board when your taking out blown transistors necessitating the replacement of the board.
How big can the wires to the battery be with those connectors. I understood people to say the bigger the better and was considering bolts for lugs for mine.
The other question I have is the number of circuits. I've seen on this forum that building multi-coil machines we should have 4 circuits per coil. Can you have 4 circuits?
Actually, you can probably forget my questions, because you'll get input from John, and if you build your board the way he says, I'll build my machine to match your board.
thanks,
h

[ErikN]

Howard,

I too have blown my share of transistors, but there are no plans for socketing the transistors; all of John's transistors are soldered. I expect the terminal blocks I used will be alright for small to medium setups, but they don't accept wire larger than about 14ga. A 4 transistor board is also in the works, but I have more work to do on it, including finding suitable terminals that accept larger wire.

Regarding desoldering, I would recommend a solder sucker and some braided copper desolder wick. When I have to replace components, these are lifesavers. If I'm replacing a component I know is bad, I will usually clip all the legs first and then remove each leg individually. After that, you can use the solder sucker or wick to get the remaining solder out of the pad.

Once one starts matching components, especially on a multi-board/coil machine, you'll want to quadruple check all your connections. Blowing a single component in a matched set, means you'll have to search for components that match the rest. This gets increasingly challenging as your machine gets bigger because you need more components.

The picture of the second board (with the heat sink) has 3 matched transistors, each has an hfe of 49 and the 3 base resistors are matched within .002 ohms

Erik

[John_Bedini]

Erik,
It would be possible to use the terminal blocks to screw the transistors in, like the Bata tester I showed you. That way you could satisfy everybody providing they used the MJL or the MJW transistor they would both fit. just an idea.
John

[ErikN]

Erik,
It would be possible to use the terminal blocks to screw the transistors in, like the Bata tester I showed you. That way you could satisfy everybody providing they used the MJL or the MJW transistor they would both fit. just an idea.
John

Thanks John, I'll think on this and see what I can come up with.

Erik