Tracor Northern TN1705 and TN1706 Pulse Height Analyzers

[marconmeteo]

tn1705doc.pdf

tn1705schema.pdf

Technical Notes

Changing from 20mA to EIA RS-232 serial output

Board-C contains two jumpers for changing the serial output from 20mA current output to EIA RS-232 output.

To select the EIA option, install the jumper from U3-4 (74LS04) to the 4K7 resistor. Remove the jumper from U3-3 to 4K7 resistor.Install the jumper from 3K3 resistor to -12V. Remove the jumper from the resistor to GND. See photo.



Changing from 1200 to 4800 baud

Serial output is on DB-25, pin-1 and GND is pin-25. Normal baud is 110. To change to 1200 baud, jumper pin-14 to GND.

To change the 555-timer circuit from 1200 baud to 4800, modify Board-E as follows. See photo.

TN1705_555.png

Replace 4K02 resistor with 2K2.
Replace 1K96 resistor with 2K2.
Relplace 0.0082uF capacitor with 2n2F.
Replace 0.033uF capacitor with 10nF.
Remove 0.01uF capacitor at TTIN input.

If an extender card is not available, apply +5V to the board and adjust 1200B-ADJ trimpot for 76.8KHz output at 555-timer U32-3.


Data Loss

Incidences of data being lost have been experienced when the HORIZONTAL switch is changed from 1/2 to 2/2. An attemp to fix this problem involves a minor modification to Board-C.

Cut trace leading into U29-13 (74LS75) - signal R
Connect U29-13 (74LS75) to signal CS from U24-5 (74LS221).