Vectronics VEC-422K - Manual (Page 19)

VEC-422K Owner's Manual SCA Decoder Kit
17
The assembly of the VEC-422K SCA decoder is completed.
TESTING AND ALIGNMENT
Testing: The final test is proving the SCA adapter works with your receiver.
Here are few simple voltage tests to check out the adapter.
Note: Nine volt battery attached and SW1 on (shaft latched inward).
U2 LM386 9 volts at pin 6. About 4.5 volts at pin 5.
U1 XR2211 9 volts at pin 8.
The following tests need only be performed if you have access to the required
test equipment. The advanced test proves that the unit is working flawlessly.
Advanced test: Using a function or audio generator, inject a 60-mV P-P 67-kHz
sinewave into jack J1. Monitor pin 11 of the XR2211 with a scope (.1-volt per
division, AC coupled, 10uS sweep per division). Observe the scope signal while
slowly rotating tuning control R16. The scope pattern should change from a
jittery pattern to a stable triangular waveform (about .3-volts P-P) when lock is
achieved.
Some function generators will accept a VCG input (such as the Wavetek model
III). Apply audio to the VCG input to FM modulate the 67-kHz signal. When
tuned for lock, the modulating signal should be audible in the monitor speaker
(jack J4 output). Adjust the volume control for best level. Vary the signal
generator output from 50kHz to 100kHz in several steps, and tune for lock at
each frequency.
Alignment: There is no alignment required for this project. It is ready to enjoy
when assembly and testing are completed!