Nicolet 526

The Nicolet 526 is a signal averager that is used in a modified OEMed Tektronix 5110 (5103N/D10) mainframe. The modifications to the mainframe performed by Nicolet include

adding a perforated panel for fan cooling via the bottom panel of the scope,
adding a 12-pin connector on the rear panel of the scope
connected the 12-pin connector to the interface board, connector J604.

The 526 has its own +5V regulated rail. An external source of +7V unregulated DC is routed from thee 12-pin rear connector to the mainframe interface board, and into the plug-in. An LM323 +5V three-terminal regulator is the source of the +5V rail within the Nicolet 526. (Even though the input is marked "+7 UNREG" on the board, it should probably be +7.5V minimum, per the LM323 datasheet.) Since the LM323 is rated for 3 amperes, it is unlikely that the plug-in sinks more than that from the "+7 UNREG" input.

How does the Nicolet 526 get the horizontal signal to the scope if it only plugs into the right vertical plug-in interface connector? In a standard, unmodified 5103, there is no signal path from the right vertical connector to the horizontal amplifier.

Mechanically, the Nicolet 526 is a three-bay 5000-series plug-in. It mates with the center-bay plug-in connector. The Nicolet 526 is made of four boards and a backplane. Connection to the Tektronix mainframe is done via thee backplane. The four boards are:

ADC and Register: The SIGNAL wire from pin 23A on the plug-in interface goes to the inverting input of an LM301 opamp via a resistance of around 165 kΩ. The noninverting input of this opamp is grounded.
Address
Control
Memory

The design makes heavy use of 7400-series digital logic in DIP packages. The printed circuit boards are two-layer. The memory is an array of Fairchild 2102DC MOS 1k x 1 static RAM ICs, DIP, soldered in place.

The wires connecting the backplane board on the 526 to the mainframe interface connector on the 526 are labeled:

H LOCK TRIG (white w/ black stripe), pin 27B of the plug-in connector
TRIGGER (light violet) 26A
RO TRIG (violet) 26B
Y LOCK IN (blue) 25B
FID SIG (green) maybe "FID" stands for "Free Induction Decay" in NMR? 24B
SIGNAL (brown) 23A
RO STUS (yellow) 23B
+7 UNREG (black), pin 22A and 22B of the plug-in connector
+7 UNREG (black), pin 22A and 22B of the plug-in connector
GND (white) 14A and 14B (standard 5000-series pinout)
GND (white) 14A and 14B (standard 5000-series pinout)
-VERT SIG (white w/ red stripe) 13B (standard 5000-series pinout for vert CH2)
+VERT SIG (white w/ brown stripe) 13A (standard 5000-series pinout for vert CH2)
-HORIZ SIG (white w/ orange stripe) 11B
+30 (red) 5A (standard 5000-series pinout)
-30 (orange) 5B (standard 5000-series pinout)
11A is jumpered to 14B at the male plug-in connector of the 526.

The 12-pin rear-panel connector has its pins numbered on the inside of the connector.

Pin	Function	Comment
1
2
3
4
5
6
7
8
9
10	Ground
11
12

Front
Top
Left
Right
Bottom
ADC and Register
ADC and Register
Address Board
Address Board
Control Board
Control Board
Memory
Memory
Rear
Top front
Right front
Bottom front
Mainframe rear connector internal
Mainframe rear connector external
Mainframe rear connector to J604