FSB 280 - UPDATING STROBE 5 AND OMC BOARDS IN THE FIELD.

12-NOV-92

Overview

STCL recently published two FCO's concerning the Strobe 5 and OMC boards.

1. For Strobe 5 board, FCO no. 16850. Its purpose is to:
   
   a. Prevent PLL locking problems at start of plot by limiting minimum VCO input voltage to 2V at a low range and 4.5V at a high range.
   
   
2. For OMC board, FCO no. 16660. Its purpose is to:
   
   a. Improve A/D precision for light calibration.
   b. Add GND connection between OMC board and data cable to prevent false cable effects.
   c. Change Data Channels PAL U609 to enable connection of Data B (another host) as well.

Both FCO's ask you to replace the boards with new boards having different comp. levels.

However if you need to perform these FCO's and you cannot get immediate replacements, you can perform part of the changes in the field.

The following explanation describes the minimum changes that the board can undergo in order to solve the problems described above.

(Do not change the comp. level of the boards.)

STROBE 5 (503D2753)

The Problem

1. Shifts on the start of plot or on the gray scales area.
   
2. Corruption of the exposed file. The red led (of the PLL unlocked) on the Strobe 5 board lights up in a bright color all through the exposure.

The Changes (see the attached scheme)

1. Disconnect, on the print side of the board, DZ2 (the side that leads to R102).
   
2. Connect, on the print side of the board, resistor R100 (20K) between the disconnected pad of DZ2 and the disconnected pad of resistor R102.
   
3. Connect, on the print side of the board, diode CR1 (1N914), the catode to R102 (the disconnected pad) and the anode to U102-1.
   
4. Connect, on the print side of the board, diode DZ6 (1N5222B) 130B02500 the catode to U101-1 and the anode to anode of the diode CR2 (1N914) cat. no. 130A07500. Connect the CR2 catode to TP7.

Test Procedure

1. Run diagnostics on the Strobe 5 board and check that all tests pass.
   
2. Expose several files and check that the problem doesn't reappear.

OMC BOARD (503D28273)

(You can perform the following changes separately according to the problem.)

The problem

If you want to enable data port B for PS/2.

The change

Replace PAL (U609) cat. no. 107K8A434 with PAL (U609) cat. no. 107K8A434A.

Test procedure

Connect the PS/2 data cable to port B and try to plot from PS/2. Check the exposure for acceptable results.

The problem

Problems with lines on exposure due to distortion in the information passing the data cable.

The changes

1. Disconnect J1-1 in the print side of the board.
   
2. Disconnect J2-1 in the print side of the board.
   
3. Connect J1-1 to J2-1 and to the DGND U807-10.

Test procedure

1. Run diagnostics and verify that all tests pass.
   
2. Expose several files and check if the problem disappears.
   
3. The problem

Light stability between different exposures with same calibration value.

The change

1. Replace capacitors C110, C108 from 0.1æF (cat. no. 151K41001) to 100 PF (cat. no. 151K11001).
   
2. Replace capacitors C101, C106 from o.047æF (cat. no. 151K34701) to 33 PF (cat. no. 151K03301).

Test

1. Expose a few files and check for no density variation between the files.