Buying the parts : which, where, equivalents, rare parts, price, BOM, Mouser cart... ?
Corrections : fixes, improvements, differences with other 208... ?
Building : difficulty, help, calibration... ?
Expanding and interfacing : cards, expanders, negative CV... ?
Keyboard : 218 ? tracking, external controllers... ?
Buying the parts
Do you or a third party offer full kits with all the parts needed ?
SAmodular offers parts, kits and bundles.
Should I spend undue money on expensive obsolete rare parts ?
Contrary to what some may believe or claim, there's no magic contained in old electronic parts and the expensive obsolete rare ones can be replaced without impact on the sound or behaviour, details below.
What makes a nice sounding and good working synth is neat build, careful selection on test of some components, precise calibration and basic understanding of how things work. No snake oil or esoteric belief will ever make up for the lack of any of these.
This is valid for all 208 revisions and for all synths in general.
The tips, observations and opinions shared here come from my years of experience building and repairing synths and audio gear.
Of course, feel free to use the parts you want, to experiment and compare by yourself and come to your own conclusions, it's part of the DIY fun.
Can I replace the µA726 / UA726 ?
This part is insanely and unduly expensive, therefore the PCB set includes a pair of pA726, a very good working drop-in replacement. This doesn't affect the oscillator's sound or timbre in any way and the tracking and stability are better than with µA726 / UA726.
The cards 6 and 7 have the original layout, so if you have money to waste and do care more of vintage hype than performance, you can use µA726 / UA726 instead of the pA726.
Beware of the cheap Chinese ones, these are most likely fakes that at best won't work but might also damage other parts in the circuit.
Can I replace the 2N4339, 2N4340, 2N4341 ?
The cheap J201 available on eBay works fine instead of those and doesn't impact the sound or behaviour. Other JFET's selected on test should work as well.
I've seen some J201's in Q1 on card 7 (2N4341) cause the MO to slightly modulate the CO, if you notice this unwanted behaviour, select another J201 on test to fix it.
Only in Q1 on card 8 (2N4339) I couldn't get a proper CO sine with a J201, a selected SMP4339 works fine thanks to this adapter.
Can I replace the 2N3565 ?
The PN3565 works fine and doesn't impact the sound or behaviour. It should be mounted this way.
Can I replace the MC846P ?
Dave Brown explains how to replace it with a 74LS03. This doesn't impact the sound or behaviour.
Can I replace the LS352 / 2N3806 / MAT03 ?
The 2N3807, 2N3810, ECG82... work fine and don't impact the sound or behaviour. Other matched PNP transistors pairs with similar specs should work as well.
Can I replace the 2N1711 ?
The 2N3019 is a drop-in replacement and various other NPN transistors should work, the 2N1711's are used as a LED driver.