◊ PCB Documentation

144 Dual Square Wave Oscillator

Two independent oscillators in one unit. Frequencies are continuously variable from 5 cps to 20 kc and may be controlled internally or with externally applied voltages. There is provision for wide band amplitude and frequency modulation.

• Dual Squarewave Oscillator Schematic.
• Mike Peake's build notes with PCB artwork from his Ebolatone blog.
• FPD front panel file (New!)

PCBs are $25.00 @ — ORDER HERE

Bill of Materials (value/qty)

• Resistors
  • 10R x 2
  • 1K x 2
  • 10K x 18
  • 1K5 x 4
  • 15K x 4
  • 2R2 1/2 watt x 2
  • 220R x 2
  • 2K2 x 12
  • 22K x 6
  • 220K x 2
  • 330K x 2
  • 3K6 x 4
  • 470R x 2
  • 4K7 x 6
  • 47K x 4
  • 68K x 4
  • 900R x 2 (or 910R)
  • 1K trimmers x 8
  • A50k audio taper potentiometers x 4
  • B10k linear taper potentiometers x 2
• Capacitors
  • 47pf x 2
  • 100pf x 4
  • 910pf x 6 (can sub .001uf)
  • .001uf x 2
  • .0022 x 2 (polystyrene)
  • 1uf x 2 (tantalum)
  • 15uf x 4 (tantalum)
  • 56uf x 2 (tantalum; can sub 47uf)
• Semiconductors
  • 1n457 x 10
  • 2n5550 x 4
  • 2n4916 x 4
  • 2n3391 x 2
  • 2N5020 2N5460
  • 2n3565 x 6
  • J201 x 2
• Misc.
  • .156" 4-pin power header x1

*Errata/Notes

• Note: In the original schematic, there is an error in the expo-converter section, first identified by the inimitable Don Tillman (nice circuit analysis there, too). On the schematic, R38 (47Ω) is shown tied from Q8 to several of the other transistors; it should instead be tied from Q8 to V+. This correction is made on our PCB.
• Transistor substitutions:
  • Q1/Q2, NPN matched pair: IT-122 is unobtainium - substitute 2n5550 (a matched pair of 2n3904 may also be used)
  • Q3/Q5, 2N4916 PNP: technically obsolute but pretty easily available NOS; 2N5401 would be a recommended replacement (check pin-out)
  • Q4, 2N3391 NPN: currently available from Mouser
  • Q6, P-channel FET: U47 is unobtanium, substitute 2N5020 2N5460 (thanks Mike Peake for the updated recommendation)
  • Q7-Q12, 2N3565 NPN: currently available from Mouser as PN3565
  • Q15, N-channel JFET: E101 is unobtanium, substitute J201
• Some builders have substituted 2n3904 for all NPN and 2n3906 for all PNP transistors, across the board; I've not tried this yet myself.