Ramsey Electronics Treasure finder TF-1 Instruction Manual page 11

18. Install C18, a .01 uF mylar capacitor (marked 103). We chose to use
a mylar cap in this position because mylar caps show greater stability
than standard ceramic disc caps; and since this is used in the oscillator
frequency determining section we wish to keep this value as "rock solid"
as possible.
19. Install U1, the NE602 mixer oscillator IC. Make sure to align the
notch or dot associated with pin one with the notch shown in the parts
layout diagram. Also check to be sure all 8 pins are through the board
before soldering the IC in place. This IC is responsible for the local
oscillator and mixing circuits and replaces a few dozen discreet
components.
Great job! Take a moment now to check your previous solder joints for
"opens" where the solder did not completely flow around the connection or
solder "bridges" between closely spaced pads or IC pins. The best time to
identify this type of problem is now when you're focused on this section of
the board, saving you from problems later on.
Let's continue with the search coil oscillator section of the treasure finder.
20. Identify the small signal transistor Q1 (three leads marked 3904).
Notice that there is a "flat" side of the component. Install transistor Q1,
being sure to mount the flat side as shown in the parts diagram.
21. Install R8, 270 ohm (red-violet-brown).
22. Install C7, a .01 uF mylar capacitor (marked 103). Again, being an
integral part of the oscillator circuit we are installing a high quality mylar
type.
23. Identify and install C5, the .0015 uF disc capacitor (marked .0015 or
1500K). Keep those leads as short as possible.
24. Install C3, .1uF disc capacitor (marked 104).
25. Install R3, 10K ohm (brown-black-orange).
26. Install R2, 120 ohm (brown-red-brown).
27. Install R5, 10K ohm (brown-black-orange).
28. Install C6, .01 uF disc capacitor (marked .01 or 103 or 10nF).
29. Install C11, .1uF disc capacitor (marked 104).
30. Install R6,1K ohm (brown-black-red).
TF1 • 11