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Maintenance
MT930B
Service Manual
Page 6-45
Audio IF Filter Check
Check Conditions:
•
Input: 6.8 MHz CW at –20 dBm
•
Output: JB01.
•
#2 BW: 880 kHz
•
#3 BW: 880 kHz
•
Subcarrier frequency: 6800 kHz
Check Procedure:
1. Connect the DC voltmeter between pins 1 and 4 of JA41 for #2, and note
the signal meter voltage.
2. Increase the carrier wave level 3.0 dB more than noted in step 1.
3. Vary the carrier wave frequency, and find the frequency equivalent to the
signal meter voltage noted in step 1.
4. Calculate the difference, and set to a –3 dB bandwidth.
5. Increase the carrier wave level 20.0 dB more than noted in step 1.
6. Vary the carrier wave frequency, and find the frequency equivalent to the
signal meter voltage noted in step 1.
7. Calculate the difference, and set to a –20 dB bandwidth.
8. If the values calculated in steps 4 and 7 do not satisfy the latest specifica-
tions, adjust LC41, LC42, and LC43 for #2 or LC71, LC72, and LC73 for #3.
Audio 880 kHz Filter Adjustment
Perform the following adjustment if the bandwidth does not satisfy the specifica-
tions when the BW is 880 kHz for AUDIO #2 or #3.
Adjustment Conditions:
•
Scalar Network sweep frequency: 6.8
±
2 MHz
•
Scalar Network output level: 6
±
2 dBm
•
BW: 880 kHz
•
Subcarrier frequency: 6800 kHz
Adjustment Procedure:
1. Set the variable attenuator to –39 dB, and connect a detection probe after
passing through an amplifier to perform any correction.
2. Connect the output of the variable attenuator to JB01, and set the attenua-
tion level to 0 dB.
3. Connect the amplifier input to JB42 and JB72 for #3.
4. Adjust LC41, LC42, and LC43 for #2, and LC71, LC72, and LC73 for #3.
Содержание mt930b
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Страница 10: ...General Information Page 1 4 Service Manual MT930B THIS PAGE INTENTIONALLY LEFT BLANK ...
Страница 22: ...Controls and Connections Page 3 4 Service Manual MT930B THIS PAGE INTENTIONALLY LEFT BLANK ...
Страница 86: ...Options Maintenance Page 7 2 Service Manual MT930B THIS PAGE INTENTIONALLY LEFT BLANK ...
Страница 90: ...Drawings Page 9 2 Service Manual MT930B 10264 Figure 9 1 MT930B Block Diagram 1 ...
Страница 91: ...Drawings MT930B Service Manual Page 9 3 10265 Figure 9 2 MT930B Block Diagram 2 ...
Страница 92: ...Drawings Page 9 4 Service Manual MT930B 10266 Figure 9 3 MT930B Block Diagram 3 ...
Страница 93: ...Drawings MT930B Service Manual Page 9 5 10267 Figure 9 4 MT930B Block Diagram 4 ...
Страница 94: ...Drawings Page 9 6 Service Manual MT930B 10268 Figure 9 5 MT930B Head Phone Schematic ...
Страница 95: ...Drawings MT930B Service Manual Page 9 7 10269 Figure 9 6 MT930B RF PC Board Schematic ...
Страница 96: ...Drawings Page 9 8 Service Manual MT930B 10270 Figure 9 7 MT930B Converter Module Schematic ...
Страница 97: ...Drawings MT930B Service Manual Page 9 9 10271 Figure 9 8 MT930B Main PC Board Sheet 1 of 3 ...
Страница 98: ...Drawings Page 9 10 Service Manual MT930B Figure 9 9 MT930B Main PC Board Sheet 2 of 3 ...
Страница 99: ...Drawings MT930B Service Manual Page 9 11 10273 Figure 9 10 MT930B Main PC Board Sheet 3 of 3 ...
Страница 100: ...Drawings Page 9 12 Service Manual MT930B 10274 Figure 9 11 MT930B Power Supply Schematic ...
Страница 101: ...Drawings MT930B Service Manual Page 9 13 10275 Figure 9 12 MT930B IF Filter Block Schematic ...
Страница 102: ...Drawings Page9 14 Service Manual MT930B 10276 Figure 9 13 MT930B Audio IF PB01 Schematic ...
Страница 103: ...Drawings MT930B Service Manual Page 9 15 10277 Figure 9 14 MT930B Audio Out Schematic ...
Страница 104: ...Drawings Page 9 16 Service Manual MT930B 10278 Figure 9 15 MT930B Audio PW01 PC Board Schematic ...