Kenwood FG-273 Service Manual page 7

ADJUSTMENT
SINE WAVE AMPLITUDE ADJUSTMENT
1. Push function switch to "SINE WAVE".
2. Push range switch to 100 kHz, dial scale setting at 1.0
position.
3. Load 50 ohms, ATT switch OFF, amplitude VR MAX.
4. Adjust R75 (sine wave output amplitude) to get
10.4 ± 0.1 Vp-p level from main output and make sure
the waveform do not clip on the top and bottom.
SINE WAVE, FREQUENCY RESPONSE AD-
JUSTMENT
1. Push function switch to "SINE WAVE".
2. Push range switch to 1 M, amplitude VR MAX.
3. Turn the frequency dial to 2.0 position approximately.
4. Load 50 ohms, A TT switch OFF.
5. Adjust C23 (sine wave response) to get 1 0.4 ± 0. 1 Vp-p
level from main output and make sure the signal are not
clipping.
SINE WAVE DISTORTION ADJUSTMENT
Set sweep width VR, rate VR, duty VR, offset VR to mini-
mum situation. Offset VR press in to internal offset position.
1. Push function switch to "SINE WAVE".
2. Push range switch to 100 kHz.
3. Tuning frequency dial to 0.2 position.
4. Adjust R35 make potential equal (within ± 10 mV) be-
tween 05 gate and pin 10 of U5.
5. Adjust R11, R19 make DC voltage equal between pin
2 and pin 3 of both U 1 and U2.
6. Push range switch to 100 Hz, adjust R45 CW to MAX.
7. Adjust R48 to reduce 20 Hz distortion.
8. Readjust R45 to reduce 20 Hz distortion.
9. Repeat step 7 and 8 to minimize 20 Hz distortion for
less than 0.8%.
10. Pu!?h range switch to 100 kHz, setting frequency dial
to 1 .0 position.
11. Check distortion of 100kHz for less than 0.8%.
12. Repeat step 7 to 8 for maintain distortion less than
0.8%.
FREQUENCY ACCURACY ADJUSTMENT
1. Push function switch to triangle wave.
2. Push range switch to 100 kHz, amplitude VR MAX.
3. Tuning frequency VR to 2.0 position.
4. Adjust R7 for a counter display reading 200 kHz.
5. Check all ranges accuracy and function are in full scale
±4.5%.
6. Repeat steps 4 and 5.
7. Tuning frequency VR to 0.2 position.
8. Check all function and frequency except MHz range fre-
quency accuracy are in full scale ± 4. 5%.
9. Repeat steps 3 to 7 to complete step 8.
1 M RANGE FREQUENCY ADJUSTMENT
1. Push function switch to triangle wave.
2. Push range,switch to 1 MHz, amplitude VR MAX.
3. Tuning freqUency VR to 2.0 position.
4. Adjust C8 for a counter display reading 2 MHz.
5. Tuning frequency VR to 0.2 position.
6. Check all function frequency accuracy is in full scale
±4.5%.
7. Repeat steps 3 to 5 to complete step 6.
COUNTER SENSITIVITY ADJUSTMENT
1. Push the counter INT/EXT switch to EXT mode, dial
scale setting at cw max.
2. Set range switch at 1 M range. amplitude VR max,
function switch setting at triangle.
3. Adjust R159 to make reading '
1 .0"
with no signal in-
put to EXT counter input BNC jack.
4. Check counter sensitivity by 10 MHz 30 mV RMS.
5. Repeat step 3 and 4 to maintain both sensitivity spec
and repress interfere of signal generator circuit.
COUNTER ACCURACY ADJUSTMENT
1. Warm-up the instrument at least thirty minutes.
2. Input 10 MHz 30 mVrms sine wave to EXT counter
BNC connector.
3. Push the range mode switch to 1 k range (gate time
1 s) adjust C43 SVC to 000.000 kHz (OVER LED lights
on simultaneously).
LOG SWEEP WIDTH ADJUSTMENT
1. Pull rate control VR and turn C.W.
2. Connect oscilloscope input to TP1.
3. Adjust R176 (470 ohm) to get
+
13.5/-0.5 V log
wave form.
7