RF Test Oscillator (May/June 1996): The PCB overlay diagrams have a number
of errors:
1. C29 (22nF) is incorrectly identified as C30
2. C26 (0.1uF) is incorrectly identified as C29
3. C30 (0.1uF) is incorrectly identified as C31
4. C27 (0.1uF, bypassing pin 5 of U12) is incorrectly identified as C26
5. C31 (0.1uF, between Q7 and Q8) is not identified
6. R39 (180 ohms), is incorrectly identified as R38 and shown as 150 ohms
7. R34 (220 ohms) is incorrectly identified as R35
8. R38 (470 ohms) is incorrectly identified as R34
9. R33 has a value of 15k, not 33k as shown
10. R35 (1M) is incorrectly identified as R39
The parts list also has some errors:
11. R22 is shown twice; the correct value is 47 ohms
12. R39 should be shown with a value of 180 ohms
13. C15 and C16 should have a value of 4.7nF
14. C20 should have a value of 2.2uF
15. C29 should have a value of 22nF
16. U12 is not listed. It's a TL072/LF353
Also the schematics show C4 (2.2uF) on the output side of U10, whereas it's
on the input side as shown on the PCB overlay. Similarly the supply for R13
and the tuning pot is taken from the 'source' side of R24, not the 'load'
side as shown in the schematic.
Note that it may also be necessary to reduce the value of R22 with some
units, to achieve a clean audio sinewave.
Our apologies for the above errors, and our thanks to reader Mr D.J.
Cardwell of Guildford, NSW for pointing them out.