Adjustment - Kenwood FG-273 Service Manual

ADJUSTMENT
CASE DISASSEMBLY AND ASSEMBLY
1. To open the case, turn the unit upside down with the
rubber feet facing up. (See Fig. 2)
2. Remove the four screws from the bottom case.
3. Carefully separate the two halves of the case and
recalibrate the unit following the prescribed procedure.
SCREWS
Fig. 2
4. To close the case, lower the bottom case and guide the
front and rear panels into thier slots. Position the rub-
ber feet as illustrated and screw the two halves of the
case together.
Do not overtighten screws.
100/120/220/240 VOLT CONVERSION
This instrument operates from a 100 V, 120 V, 220 V or
240 V AC, 50 to 60 Hz line-voltage source. The applied vol-
tage is indicated on the rear panel. To convert from the
specified voltage to other line voltages, replace the voltage
plug position on PC Board, referring to the figure below and
change the rear panel applied voltage indication. Also, be
sure to replace the fuse to correspond to the line voltage
0.3 A slow-blow fuse for 100 V to 120 V operation and
0.2 A fast-blow fuse for 220 V to 240 V operation. If it is
not wired to your local line voltage, set the power trans-
former wiring as shown below. (See Fig. 3.)
II I I
II I I
TRANSFORMER I
6
~ 100V
120V
220V
240V
Fig. 3
TEST EQUIPMENT REQUIRED
• Digital Multimeter: KENWOOD DL-707 or equivalent
• Osilloscope: KENWOOD CS-1 022 or equivalent
• Frequency Counter: KENWOOD FC-756 or equivalent
• Distortion Analyzer: Y.H.P 334A or equivalent
• DC Power Supply: KENWOOD PD 1 8-1 0 or equivalent
AMPLIFIER INTERNAL DC OFFSET AND TRIAN-
GLE WAVE AMPLITUDE ADJUSTMENT
1. Push function switch to OFF position, load 50 ohms.
2. Push range switch to OFF position, ATT switch OFF.
3. Amplitude to minimum.
4. Adjust R88 to get - 5 mV at the main out BNC jack.
5. Push function switch to "TRIANGLE WAVE", setting
amplitude VR at maximum.
6. Push range switch to 100 kHz.
7. Tuning the frequency dial to 1 . 0 position approximately.
8. Adjust the resistor R91 to get 10.4
±
0.1 Vp-p main out-
put level and make sure the wave form are not clipping.
9. Check all range except MHz that triangle wave output
amplitude more than 10.25 Vp-p.
10. Re-adjust resistor R91 to obtain 10.25 Vp-p output at
any critical frequency point.
11. Repeat step 1 to 4 to maintain 5 mV DC voltage at
main output BNC.
TRIANGLE WAVE FREQUENCY RESPONSE AD-
JUSTMENT
1. Push function switch to "TRIANGLE WAVE".
2. Push range switch to 1 MHz, amplitude VR MAX.
3. Tuning the frequency dial to 2.0 position approximately.
4. Load 50 ohms and A TT switch OFF.
5. Adjust the C 13 to get 10.4
±
0.1 V main output level
and make sure the wave form are not clipping.
SQUARE WAVE RISE & FALL TIME ADJUSTMENT
1 . Push function switch to
I I
SQUARE WAVE", amplitude
VR MAX.
2. Push range switch to 100 kHz.
3. Tuning frequency dial to 2.0 position.
4. Load 50 ohms, A TT switch OFF.
5. In maximum output amplitude condition, adjust C25 to
reduce over shoot phenomenon.
6. Push range switch to 1 MHz, check rise/fall time for less
than 100 ns.
7. Repeat step 5, 6 to minimize over shoot and maintain
rise/fall time.
SQUARE WAVE AMPLITUDE ADJUSTMENT
1. Push function switch to "SQUARE WAVE".
2. Push range switch to 1 MHz, amplitude VR MAX.
3. Tuning frequency dial to 2.0 position.
4. Load 50 ohms, A TT switch OFF.
5. Adjust R79 (square wave output amplitude) to get
10.4
±
0.1 Vp-p main output level.