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| == Power Supply and Filament Supply Regulator == | | == Power Supply and Filament Supply Regulator == |
| The external power supply unit generates all the B+ Voltages (-150,+100,+225,+330,+350 and +500V) required by the indicator unit. | | The external power supply unit generates all the B+ Voltages (–150, +100, +225, +330, +350 and +500 V) required by the indicator unit. |
| This is fed to the indicator unit through the interconnect cable.
| | These are fed to the indicator unit through the interconnect cable. |
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| | There are two transformers inside the power supply unit – one to generate heater voltages (except for the tubes noted below), the other to generate all the B+ plate voltages. |
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| The heater/filament supply for all the tubes inside the indicator unit are generated by a transformer inside the indicator unit. | | The heater/filament supply for all the tubes inside the indicator unit are generated by a transformer inside the indicator unit. |
| Output of this heater/filament transformer is regulated by the external power supply unit by controlling the primary voltage to it.
| | A saturable inductor, located in the power supply unit, is connected in series with its primary as the control element of an AC regulator circuit. |
| | | One 6.3 V winding from the indicator unit filament transformer is fed back through the interconnection cable (part number [[012-032]]) |
| There are two transformers inside power supply unit. One to generate heater voltage for all the tubes which dont get a regulated heater voltage from Indicator unit.
| | to supply heaters of specific tubes in the power supply unit (V624, V634, V664, V684, V694). Moreover, a regulator Tube (2AS-15, a |
| Second transformer is used to generate all the B+ plate voltages. There is also a saturable reactor inside the power supply, which is part of AC regulator for heater transformer inside indicator unit.
| | Temperature Limited Diode) is used to sense this filament voltage and derive a control DC current through the saturable inductor, |
| | | thereby signal closing the control loop. |
| Regulation of the filament supply happens as follows:
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| The power supply sends and control AC to the primary of the filament transformer in the indicator unit through the interconnection cable .
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| There is a feedback loop that is formed between the indicator unit and the power supply unit. This is achieved by sending one 6.3V winding output of the heater/filament transformer in the indicator unit through the interconnection cable (part number [[012-032]]) back to the power supply unit.
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| This performs two functions.
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| First, it is used to heat the cathodes of specific tubes in the power supply unit - V624,V634,V664,V684,V694.
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| Second, this filament voltage is the feedback signal to a filament voltage regulator in the power supply.
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| A regulator Tube - 2AS-15, a Temperature Limited Diode - is used to sense this filament voltage and uses it to control DC current through a saturable reactor.
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| The voltage to the primary of the heater/filament transformer in the indicator unit is fed through this saturable reactor and send to the indicator unit via interconnection cable (part number [[012-032]]). This forms a closed loop to regulate heater voltage in the indicator unit.
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| One of the consequences of this scheme is that it the power supply unit will not energize the plate voltages (except +100V) without the indicator unit connected.
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| This is because of the following reasons:
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| 1. Heater to V624,V634,V664,V684,V694 are taken from the 6.3V feedback line coming from filament transformer in the indicator unit. Even though the main series pass (6080s and 12B4s) are heated from a local heater transformer, the 12AX7 comparators and 6AU6 error amplifiers are heated from the indicator unit.
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| 2. The Primary of the plate voltage transformer inside the power supply unit is looped via the thermal cutout in the indicator unit. So the plate voltage transformer in the power supply will not get power unless the indicator unit is attached.
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| Even if you try to power up power supply itself by bypassing the thermal cut-out and applying local heater voltages to the tubes which gets heater voltage from indicator unit, the power supply will not regulate as the design employs shunting resistors across the series pass tubes. Hence without load, it will not be able to provide regulation.
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| | One of the consequences of this scheme is that it the power supply unit will not energize the plate voltages (except +100 V) |
| | without the indicator unit connected, because |
| | * the 12AX7 comparators and 6AU6 error amplifiers are heated from the indicator unit, so the main series pass tubes (6080s and 12B4s) are not driven even though they are heated from a transformer in the power supply unit; |
| | * The primary of the plate voltage transformer inside the power supply unit is looped via the thermal cutout in the indicator unit, i.e. the plate voltage transformer in the power supply will not get power unless the indicator unit is attached. |
| | Even if one were to power up the power supply itself by bypassing the thermal cut-out and applying local heater voltages to the tubes normally supplied by the indicator unit, the power supply will not regulate as the design employs shunting resistors across the series pass tubes, and can therefore not regulate without a load. |
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| == Vertical Amplifier == | | == Vertical Amplifier == |