547: Difference between revisions

{{Spec | Bandwidth | DC to 50 MHz (−3 dB) with fast plug-ins ([[1A1]], [[1A2]], [[1A4]], [[1A5]]) }}

{{Spec | Rise time | 7 ns with [[1A1]] }}

{{Spec | Line voltage | 90-136 V or 180-272 V, selected via primary voltage selector (inside cabinet) and voltage range selector (on rear panel), 50/60/400 Hz }}

{{Spec | Sweep Rates | 100 ns/div to 5 s/div}}

{{Spec | Trigger Coupling | AC, DC, AC LF Rej}}

{{Spec | External Horizontal Input | 100 mV/cm to 10 V/cm, DC to 400 kHz}}

{{Spec | CRT | [[T5470]], 10 kV acceleration, 6x10 cm viewing area }}

{{Spec | Calibrator | ~1 kHz, 200 μ V_p-p to 100 V_p-p }}

{{Spec | Power consumption | 510 W }}

{{Spec | Cooling  | AC Fan }}

Rather than potting the HV transformer in wax, as was done up to that point,  

the [[120-0308-00|547's HV transformer]] was potted in epoxy.

Unfortunately, this epoxy turned out to absorb moisture over time,  

particularly when used in humid climates.

The mod he was taught by [[Jim Willams]] involves replacing the [[5642]] tube rectifiers with NTE517 diodes.

However, this this reduces the load on the regulator circuit by about 1 Watt due to the lack of tube heater filaments.  

This forces the regulator past its design limit and can result in lack of regulation, until the transformer heats up and more power is required due to losses.  

After changing to semiconductor diodes, it will be seen that grid pin 7 of V814 will be about 0 volts (fully on, with no swing to regulate)  

in an attempt to force its anode (pin 6) to about +55 V, which is the screen input of the 6AU5 (pin 8).  

The 547 has a five-stage BJT vertical amplifier that is fully differential from the plug-in

connector to the CRT vertical deflection plates. There is one tube in the vertical signal path,

a [[12AT7]] acting as a unity-gain buffer between the plug-in connector and the vertical amplifier.

The plug-in bay of the 547 has a "spoiler switch" that only enables the full bandwidth of the 547's

vertical signal path when certain relatively modern plug-ins are used, such as the [[1A1]], [[1A2]], [[1A4]], and [[1A5]].

* [[Media:Spoiler switch rationale from Tek 547 544 546 tech instr and training.pdf|Spoiler switch explanation excerpted from Tek 547 544 546 Technical Instruction and Training (PDF)]]

* [[Media:Spoiler switch rationale from Tek 547 notes.pdf|Spoiler switch explanation excerpted from Tek 547 Notes (PDF)]]

The 547's power supply provides regulated outputs of −150 V, +100 V, +225 V, +350 V, as well as a +325 V unregulated output for CRT HV section.

Multiple secondary windings feeds diodes for rectification for different voltages, using both center-tap and bridge configurations. The regulator section uses no transistors, only tubes.

There are multiple 6.3 V secondary outputs for heaters, some elevated to different voltage levels based on the section/tube that is supplied, in order to keep the heater-to-cathode voltage level within limits.

Most other power supply sections in the 547 replicate the same basic design, except slight changes in tubes used: the +225 V and +100 V regulators employ a [[6080]] as the pass element, and +350 uses a [[6CW5]].  

The plate voltage delay circuit is similar to that found in many may other Tek scopes of the same era.  A [[6N030T|6N030T delay tube (P/N 148-0021-00)]] controls a relay that switches plate supply voltages on only after the tubes are warmed up.