SWTP CT-64 Unit Log

SWTP CT-64
- Unit Log -

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 湩 capacitor in the horizontal S&H was not installed. 0.22 湩 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

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 湩 capacitor in the horizontal S&H was not installed. 0.22 湩 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.