7-6 Adjustments 8525B/8528 Technical Service Manual
Issue 6 Publication No: 15-02036
7.3.2 Voltage Regulators
None of the voltage regulators used are adjustable, so only their output
voltage can be checked. The location and correct output voltages are as
follows:
1. B rail regulator, 10V ±0.2V; IC1 on Motherboard.
2. +5V regulators, 5V ±0.4V.
• IC2 on Motherboard.
• IC7 on Audio and 1650kHz PCB
• IC4 on RF, Mixer, and Dual Synthesizer PCB.
• IC9 on Microprocessor Controller PCB
• IC1 on Mic Amp and Interface PCB (8530 Control Head only).
3. 26V regulator, 26V ±1V; TP7 on RF Mixer and Dual Synthesizer PCB.
4. 9V regulator, 9V ±0.25 Volts; emitter of V1 on RF Mixer and Dual
Synthesizer PCB.
These voltages should be checked with the transceiver in receive mode.
7.3.3 Crystal Oven
The oven temperature cannot be adjusted but should be checked after
allowing a five minute warm-up period. The temperature should be
approximately 60°C.
7.3.4 VCO Adjustments (RF Mixer and Dual Synthesizer
PCB)
These adjustments must be made with the metal shields in place.
VCO1
1. Select 30MHz frequency.
2. Using a DC Voltmeter or CRO, monitor TP8.
3. Adjust C42 via access hole in shield cover for 22.5V ±0.5V DC on TP8.
4. Select 250kHz; check TP8 is at 2V ±1V DC, and the ‘unlock’ LED for
VCO 1 is not lit.
VCO2
1. Select any frequency.
2. Using a DC Voltmeter or CRO, monitor TP9.
3. Adjust C79 via access hole in shield cover for 2.7V ±0.2V DC
To Next Page
Loading...
Need help?
General
