Rybett Controls WebDoc 201 (Copyright 2008) Return to [Index]
Numeritronix Execs are edit and display terminals that connect to older NC machine tools via a BTR (Behind the Tape Reader) interface. They were built by Rybett Controls and marketed by Numeritronix. The Execs were packaged in a rectangular cabinet with either a simple LED display (Exec 150) or a 9" monochrome CRT display (Exec 1501) and a vertically mounted keyboard. A key-switch on the side acts as a power switch and editor lockout. The Exec is usually mounted on top of an NC control and connected via a flexible conduit to a uP cable and BTR card. Browse or click a topic: [LED/CRT] [Display] [Keyboard] [BTR]
Exec LED displays are mounted on a printed circuit board which plugs into the keyboard behind the front panel. When replacing a single LED digit, make sure that its brightness matches the other digits to yeild a uniform look. Never clean an LED digit with harsh degreasing fluid; isopropyl alcohol is safe.
Exec CRT displays have a horizontal video driver card with small pots for adjusting size, brightness, vertical and horizontal sync just like your TV set. Many minor problems can be corrected by turning pots and wiggling connectors to clean contacts and adjust settings. You can center and rotate the display by moving tabs or rotating the coil on the neck of the picture tube.
BEFORE WORKING ON A CRT DISPLAY, TURN OFF POWER. ALWAYS STAY AWAY FROM THE FLYBACK TRANSFORMER OUTPUT WIRE TO AVOID SHOCK. THE FLYBACK TRANSFORMER LOOKS LIKE A BLACK OR RED RUBBER CASTLE.
DISPLAY as a TROUBLE SHOOTER:
The Exec 1501 CRT display is a window on many possible failures. Note the following list of symptoms:
The display is wavy: The 12 volt power supply may be out of regulation. Look at the diodes on the power supply. Check the tall capacitors and metal voltage regulators.
The CRT is filled with nonsense: There is no data communication to the CRT controller card. The CPU has probably died. Replace the 3850, 3853 or 3861 computer chip.
The CRT looks like termites are eating the left columns: The 96364 CRT controller chip on the AX131/180 card is probably unstable and should be replaced.
The display jumps and dims sporadically: A loose solder joint on the video card may be the problem. Solder all connector and transformer pins.
Newer model (Revision N) Exec built-in CRT displays and may be placed in a terminal emulation mode by pressing <Break> and then <Ctrl> T. (Just hold down the <Ctrl> or <Shift> keys and press the letter T at the same time.) When in Terminal Mode, any key pressed is sent out the serial port and any character received is displayed to the CRT. If you jumper pin 2 to pin 3 and pin 4 to pin 5 on the serial port connector behind the CRT, any key pressed should be displayed. As a first step in repairing a bad serial port, try replacing the 1488 and 1489 RS232 line driver IC chips on the AX186 UART card.
Exec keyboards are of two varieties: Exec 150 with Cherry push-button keys and Exec 1501 with Clare push-button keys. Replacement keys may be scavenged from unused key positions in the lower right hand corner of the keyboard. Or, you may order push-buttons from Rybett.
The Exec 1501 keyboard controller IC (KEY028) can sometimes collect charge on internal parasitic capacitance. If the keyboard simply stop working, unplug the Exec and try placing aluminum foil on the PCB pads of the 40 pin keyboard IC socket and let sit overnight. In the morning, remove the foil and repower the unit.
BTR INTERFACE CARD:
All Rybett/Numeritronix BTR (Behind the Tape Reader) products are designed for easy installation and removal. The heart of an Exec is an interface card and harness adapted to your machine control model.
The Exec may be placed in a Bypass condition whereby the tape reader interface card may be monitored. For an Exec 150, press the RUN and LOAD latching push-buttons. For an Exec 1501, press <Ctrl> B on the keyboard to activate Reader Bypass. Place a tape in the reader and operate the machine tool. All data should pass through the Rybett interface yet be monitored by the Exec display. If everything works in Bypass, the interface (and most of the Exec) are probably good.
If Bypass gives you trouble, you can further isolate the interface card by disconnecting the Exec cabinet from the machine tool. Replace the flexible conduit at the uP bulkhead connector on the NC control with the round (military) Deadhead cap. When the Deadhead is in place, the machine should operate from the tape reader as if the BTR was never there. If the deadheaded interface works with tape, there is no need to repair it.
If the interface card does not work in a deadhead state, remove it entirely and replug the original machine tool wiring. You should try testing the machine tool with all BTR parts removed to see if the NC tape reader logic is working properly.