Ramsey Electronics FR146 Instruction Manual download pdf (Page 10)

SR-1 – 10

shielded transformers can be installed, their internal capacitors need to

be removed. Looking at the underside of these two transformers, you'll

see a tubular part, probably white with a brown band, somewhat like the

resistors in this kit. These are brittle and easily crushed with any sharp

object that can be pressed against them with mild force(small nail,

nutpick, small screwdriver). You'll find these capacitors will easily

disintegrate into particles. DO NOT do anything to the larger dual IF

transformer, L3.

 6. Install L1, which peaks or preselects the signal input from the antenna

through C1 and R1.

 7. Install U1, the NE602 IC mixer oscillator. The marked end of the IC

(band or dot) must face the FRONT of the PC board (the end with the

switch and dials.) If you wish, install an 8- pin DIP socket, still

remembering to orient and install correctly. Please don't be afraid to

solder U1 directly to the PC board, as we have seen more repair

problems associated with DIP sockets than from direct soldering of IC

chips!

 8. Install C2, .01 µF (marked .01 or 103). C2 will bypass pin 2 of the

NE602 to ground. The antenna signal coupled through C1, level

controlled by R1, peaked by L1 is now fed to input pins 1 and 2 of the

NE602. Pin 3 of the NE602 is now connected to ground, as required.

 9. Install C16, a large 100 or 220 µF electrolytic. The positive side must

face towards the NE602. (Note: The prominent stripe on the side of the

capacitor usually designates the negative side, not the positive side).

 10. Install Q4, NPN 2N3904 next to C16. Note the orientation of the flat

side.

 11. Install C3, 100 pF (marked 100 or 101), which goes across pins 6

and 7 of the NE602 IC. This capacitor is a first step in setting up the

resonant frequency of the NE602's internal oscillator, using the resonant

LC circuit to be created along with C4,L2 and the varactor tuning circuit.

 12. Install C4, 100 pF (marked 100, 101 or 100K).

 13. Install C5, .01 µF (marked .01 or 103).

 14. Install Jumper Wire, JMP1, using a scrap of bare wire trimmed from

a previously-installed part. This jumper is an "overpass" which brings +9

volts to the NE602 and varactor tuning.

 15. Near to Jumper 1, install R4, 10K [brown-black-orange].

 16. Before L2 may be installed, its internal capacitor must be removed by

crushing it with a small screwdriver or knife blade, just as for L1. Omitting

this step will prevent the oscillator from tuning the intended frequency

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Ramsey Electronics FR146 Instruction Manual Page 10