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500 Series plug-in interface

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Plug-in pinout from 535 schematic - click to enlarge

The plug-in interface of the 500-series scopes is a single 16-pin Amphenol connector.


Pin Function Comment
1 +Signal 100 mV/cm, bias +67.5 V ±2%
2 Ground
3 −Signal 100 mV/cm, bias +67.5 V ±2%
4 Int Trig GND 544, 546, 547, 549,
556, late 555 only
5 Int Trig + 544, 546, 547, 549,
556, late 555 only
6 Sawtooth 556 only, others n/c
7 Slave Pulse out 547 only
8 Multi-trace sync Cathode; grounded by CA,
M etc. in Alt Trace mode
9 −150 V min. 3.8 mA, max. 60 mA
10 +100 V min. 4.5 mA, max. 50 mA
11 +225 V min. 16 mA, max. 75 mA
12 +350 V min. 0 mA, max. 20 mA
13  6.3 VAC plug-in AC heater supply,
max. 2.8 A
14  6.3 VAC return for pin 13
15 +75 V min./max. 150 mA for DC
series heaters and LV supply 
16 Multi-trace sync Anode

Pin group function legend

 DC power and ground
 AC and heater power 
 Deflection and Trigger Signals  
 Control Signals 

Internal Trigger signal

In early 500-series systems (e.g., a Type C plug-in in a 535 mainframe), the mainframe's triggering is based on the main vertical signal (pins 1/3).

In these scopes, changing the vertical position control on the plug-in interacts with the trigger level setting if the scope is set to a DC trigger mode.

In somewhat later 500-series systems (e.g. Type 547), the plug-in (e.g. Type 1A1) provides the mainframe with a separate trigger signal on pin 5 whose DC level is not affected by the vertical position knob. In multi-trace setups, this allows consistent triggering from a specific input channel independent of which channel is currently being drawn on CRT.

For backward compatibility, the 547-era scopes have two types of INT triggering, taking the trigger signal either from the main vertical plug-in output (1/3), or the trigger output (5).

Although the Type 1A1 has two input channels, they are not identical - the pin 5 internal trigger signal is always taken from channel 1. Even later 500-series plug-ins (e.g., the Type 1A4), have a knob for the selection of which input channel's signal supplies the trigger signal. |}