[David G4EBT]

I've got three transistor testers:

Peak Atlas DCA50, which thinks JFETS are diodes
Peak Atlas DCA55 (bought cheap when on offer from Maplins). Sees it as a JFET, and states 'drain and source not identified' but correctly identifies the gate.
Cheapo Chinese jobby, which obligingly gives three options according to which test lead is connected to which pin!

Basically, none are any use whatsoever in this regard, so I relied on datasheets from which I concluded that the correct orientation is as shown in the diagram below.
I get the impression that provided the gate is correctly identified, either of the two other leads will work as source or drain so to that extent, can be considered identical.

The second pic shows an actual BF256C with the maker's pinout I.D. markings.

The third pic clarifies which lead is which on the cicuit diagram.

The fourth pic shows the PCB artwork which Ian Liston Smith, the designer, kindly provided. I assume that it was created in software intended for commercial PCB production, which doesn't lend itself to homebrew as the tracks are rather too thin and the pads too small, so I used (plagiarised!) Ian's layout to create a design which was more suited to homebrew PCB production. Though the PCB may look quite different from the original, all of the pinouts and positioning of components are identical - the only difference is that I added a current limiting resistor, which I called 'R9' to power an LED as a reminder when the Mini Mod is switched on.

When my Mini Mod didn't initially work, I eventually resolved the problem by changing over the leads of the BF256. Three years down the line, it still works a treat.

I've since made a few others as presents for friends, which have worked straight off.

I know that few are equipped or inclined to make homebrew PCBs, but many people have had success in using the laser printer 'iron on' technique, which obviates the need for a UV light box or developer. Thus, if the artwork below is 'flipped' to reverse it, and if it's printed on a laser printer onto glossy paper so it comes out 'the right way around' when ironed on. If the paper is then soaked off, it should leave the toner in position ready for etching the PCB. The worst that can happen if the process fails is that you wash off the print from the PCB, clean the board and have another go. There are countless youtube videos showing how to do it, though I'd stress that I have no personal experience of using the technique.

I hope that helps a bit.

Good luck in your endeavours Nick.