Midway Electronics is doing everything it can to keep the kit prices back at the original 1998 prices Small Wonder Labs had. In doing so we have to shop around for the best component prices without suffering quality.
Some parts may be substituted as follows:
2N3904 -- 2N4401, 2N2222A, PN2222
2N3906 -- PN3906, 2N2907, PN2907
2SC2078 -- 2SC2166, D44
MPF102 -- 2N5457 or any good N-CH FET
SA612 -- SA602, NE602, NE612
1SV149 -- MV1662
1N4001 -- 1N4002, 1N4004 or any 1 amp Schottky diode
42IF123 -- 2u6FC, 3989 but be aware these might not tune the same and they might need different capacitors and they also have a smaller screwdriver slot.
Caution must be noted on the 7.5 volt and 33 volt zeners. They could be clear glass type like the 1N4148 (do not mix them up) or they may have a silver coating on the case. In any case, use a magnifying glass to verify the correct numbers. 1N5236 7.5 V, 1N5257 33V. Do not mix them up! If you do, or want to verify, you can test them simply. See bottom of page in Construction Notes to build a test fixture. Put a resistor, 1k to 4.7k in series with the zener in question and place this across a 9 volt battery or 12 volt power supply. If you measure the voltage across the zener you should get 7.5 volts if it is the 7.5 volt zener. You will get the full supply voltage if it is the 33 volt zener.
Some capacitors have different lead spacing and markings. Take extra care when bending leads as you may separate lead from capacitor body thus destroying it.
DO NOT substitute non NPO capacitors for NPO or C0G temperature stable types. You will experience massive unwanted drift if you do.