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7104: Difference between revisions
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The 7104 uses a switch-mode power supply. | The 7104 uses a switch-mode power supply. | ||
Module A23 (schematic page <14>) contains the mains rectifier, base drive circuitry, and power transistors of the inverter (aka, switcher). | Module A23 (schematic page <14>) contains the mains rectifier, | ||
These transistors produce a 25 kHz waveform that is fed to the primary of T1310, whose secondaries provide the power for the rest of the scope. | base drive circuitry, and power transistors of the inverter (aka, switcher). | ||
These transistors produce a 25 kHz waveform that is fed to the primary of T1310, | |||
whose secondaries provide the power for the rest of the scope. | |||
Module A24 (also on schematic page <14>) contains the inverter control circuit and rectifiers for the secondaries of T1310. | Module A24 (also on schematic page <14>) contains the inverter control circuit | ||
and rectifiers for the secondaries of T1310. | |||
The inverter control circuit uses the [[155-0067-02]] inverter control IC, which is U1275. | The inverter control circuit uses the [[155-0067-02]] inverter control IC, which is U1275. | ||
Module A25 (schematic page <15>) contains the low-voltage regulators. | |||
There as independently regulated and current-limited sections | |||
for the -50V, -15V, +5V, +15V and +50V rails. | |||
Each section has an opamp and a BJT output transistor in emitter-follower configuration. | |||
The opamps need power, too. | |||
To avoid a dependency cycle, the power supplies for the opamps are separate | |||
low-current, low-efficiency zener clamps that in no way depend on the -50V, -15V, +5V, +15V or +50V regulators. | |||
The power supplies for the opamps produce -22V, -5.6V, +5.6V, and +22V. | |||
To avoid exceeding the opamps' limit of 30V total rail voltage, each opamp either gets | |||
-22V and +5.6V, or -5.6V and +22V, depending on whether it needs more output swing | |||
in the positive or negative direction. | |||
The +50V section is produces the reference voltage for the other sections. | |||
It uses a 9V zener diode, VR1412, as a reference. | |||
==Prices== | ==Prices== | ||