SWTP
CT-64
SWTP CT-64
- Unit Log -
bh

Year of Manufacture: 1977 (component date codes 7437 to 7736, most 77xx).
Date of Receipt: ~ 1998.
Source: SPARC discard.
State upon Receipt: Poor. Very messy wiring and soldering job. Some manuals and schematics.
Other Notes:
  • The screen read board is present but not fully wired in, and so is not functional.
  • The two pushbuttons and unmarked toggle switch on the front panel are not connected.
  • The user-defined BACKSPACE key is wired as ASCII BS, the unmarked user-defined key is wired as backslash and vertical bar.
  • The configuration is as detailed in the tables in the schematic.
2001 Oct: Procedure: Cleaned, original wiring removed. Rewired and reconfigured. Power cord replaced with IEC standard connector. Power switch and BNC video connector installed on back panel.
2004 Oct: Procedure: Serial communication board examined, incorrectly installed resistor corrected.
2004 Oct 08: Procedure: Powered up. Raster present and cursor functions operative, but screen filled with 'rubout' characters and characters will not change. Torquing of memory board restores proper operation.
2004 Oct 08: Symptoms: Character pixels are scattered and each character shows up on a line 3 times. Only one line of characters can be entered.
Diagnosis: Vertical frequency around 90Hz, horizontal frequency around 23KHz. Second JFET (TIS58) in horizontal reference sample-and-hold circuit has open junction. Replaced.
2004 Oct 13: Procedure: The gate resistor on the first JFET of the horizontal S&H was 220K, whereas the schematic indicates it should be 2.2M. Replaced with 1.6M.
2004 Oct 13: Procedure: 0.22 F capacitor in the horizontal S&H was not installed. 0.22 F capacitor installed.
2004 Oct 18: Procedure: Aluminum braces added to keyboard to make it more more rigid.
2004 Oct 19: Procedure: PCB trace opened on serial board to avoid shorting to ground of parity bit from keyboard with DE jumper installed. Although current seems to be limited to ~ 2mA from the keyboard scanner output when high and sinking to ground, it is not clear that shorting the output to ground is OK for the chip.



  Log
SWTP CT-64
bhilpert
2014 Jan