7104: Difference between revisions

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7104 (view source)

Revision as of 14:23, 8 April 2018

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Module A23 (schematic page <14>) contains the mains rectifier,
Module A23 (schematic page <14>) contains the mains rectifier,
base drive circuitry, and power transistors of the inverter (aka, switcher).
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,
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.
whose secondaries provide the power for the rest of the scope.


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Module A25 (schematic page <15>) contains the low-voltage regulators.
Module A25 (schematic page <15>) contains the low-voltage regulators.
There are independently regulated and current-limited sections
There are independently regulated and current-limited sections
for the -50V, -15V, +5V, +15V and +50V rails.
for the -50 V, -15 V, +5 V, +15 V and +50 V rails.
Each section has an opamp and a BJT output transistor in emitter-follower configuration.
Each section has an opamp and a BJT output transistor in emitter-follower configuration.


The opamps need power, too.
The opamps need power, too.
To avoid a dependency cycle, the power supplies for the opamps are separate
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.
low-current, low-efficiency zener clamps that in no way depend on the -50 V, -15 V, +5 V, +15 V or +50 V regulators.
The power supplies for the opamps produce -22V, -5.6V, +5.6V, and +22V.
The power supplies for the opamps produce -22 V, -5.6 V, +5.6 V, and +22 V.
To avoid exceeding the opamps' limit of 30V total rail voltage, each opamp either gets
To avoid exceeding the opamps' limit of 30 V total rail voltage, each opamp either gets
-22V and +5.6V, or -5.6V and +22V, depending on whether it needs more output swing
-22 V and +5.6 V, or -5.6 V and +22 V, depending on whether it needs more output swing
in the positive or negative direction.
in the positive or negative direction.


The +50V section is produces the reference voltage for the other sections.
The +50 V section is produces the reference voltage for the other sections.
It uses a 9V zener diode, VR1412, as a reference.
It uses a 9V zener diode, VR1412, as a reference.


The dependency relationship of the supplies is:
The dependency relationship of the supplies is:
* The -50V, -15V, +5V, and +15V sections depend on
* The -50 V, -15 V, +5, and +15 V sections depend on
** the +50V supply for reference voltage,  
** the +50 V supply for reference voltage,  
** the opamp supplies for to power their opamps, and
** the opamp supplies for to power their opamps, and
** the A24 semi-regulated rectifier outputs
** the A24 semi-regulated rectifier outputs
* The +50V depends on
* The +50 V depends on
** the opamp supplies (+22V and -5.6V) for to power its opamp,
** the opamp supplies (+22 V and -5.6 V) for to power its opamp,
** the A24 semi-regulated rectifier outputs (-54V and +54V)
** the A24 semi-regulated rectifier outputs (-54 and +54 V)
* The opamps supplies depend on
* The opamps supplies depend on
** the A24 semi-regulated rectifier outputs
** the A24 semi-regulated rectifier outputs
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