Parts Information
For general information regarding where to get parts and suggested part numbers please see
our useful Parts Guide which is linked from the TM3030 project webpage or direct at:
http://www.oakleysound.com/parts.pdf.
Some special considerations for this project
I recommend to use a close tolerance polystyrene for the VCO timing cap, C9. This will give
better pitch stability. Use a cheaper part if you can accept a small drift in VCO pitch with time.
The PCB is laid out to accept the superbly specified 10nF LCR type EXFS/HR series.
Standard axial polystyrene types will fit into the board if mounted on one end. The working
voltage can be quite low, 63V is common.
Other alternatives to polystyrene are polypropylene. But make sure you get low voltage types
like 63V or so. Polypropylene capacitors are also used in suppression and can get very very
big.
The three ceramic capacitors should be ‘low-K', NP0, or C0G ceramic plates or dipped
ceramics. The lead spacing is 2.5mm.
I have also used some axial multilayer ceramics for the power supply decoupling on the digital
sections. These parts can be substituted with ordinary low voltage radial polyesters if you
wish. Watch out for the pitch spacing as the board is laid out to accept 0.3", 7.5mm, for these
devices.
The horizontal preset or trimmer resistors are just ordinary carbon types. No need to buy the
expensive cermet types for these positions. Carbon sealed units have more resistance to dust
than the open frame types. Piher make a suitable type to use here. Pin spacing is 0.2” at the
base, with the wiper 0.4” away from the base line.
The multiturn trimmers are the ones that have the adjustment on the top of the box. Spectrol
and Bourns make these. Some types are 22 turns, while others are 25 turns. Either will do.
They should have three pins that are in a line at 0.1” pitch. Don’t chose the 10-turn ones with
the adjustment on the end, they won’t fit on the PCB.
With the exception of the differential amplifier in the filter (Q36 & Q37) all the transistors
shown as BC549 on the schematic can be pretty much any NPN transistor that corresponds to
the same pin out. For example: BC550, BC548, BC547 etc. However, I recommend using
BC549 or BC550 as these are low noise devices. A BC550 is actually just a BC549 that can
operate at a slightly higher voltage. Quite often you see an A, B or C suffix used, eg.
BC549C. This letter depicts the gain or grade of the transistor (actually hfe of the device). The
TM3030 is designed to work with any grade NPN devices although I have used BC550B in
my issue 2 prototype.
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