25 



B) Push the two bolts through the solenoid bracket. 



1) Thread each bolt with a nut, spacer, and then anothei* nut. 



2) Drill and tap two 3 mm holes 1.3 cm to each side of the 

 humidity adjustment rod and bolt the solenoid into place. 



Correcting the Response of the Humidity -adjustment Arm, 



Materials 



(1) finely-wound spring 



(2) bolts, 1.5 cm long 



Instructions (refer to Fig. 20) 



The standard spring on the humidity adjustment arm of the 

 hygrothermograph is too stiff to allow the solenoid shaft to retract 

 and record on the hygrothermograph chart. For this reason, a 

 finely-wound spring must be mounted on the arm. 



A) Remove the standard spring attached to the humidity- 

 adjusting arm. 



B) Drill and tap a 3 mm hole in the humidity adjusting arm just 

 above the securing pin of the old spring. 



C) Drill and tap another 3 mm hole in the hygrothermograph 

 base in a direct line with the hole drilled in the adjusting arm. 



D) Use the two 1.5 cm long bolts to secure the spring from the 

 hygrothermograph base to the back of the humidity adjust- 

 ing arm. The installation of this spring allows a greater 

 flexibility in the adjustment of the humidity and tension on 

 tY\,e solenoid shaft. 



Wiring the Solenoid Unijunction Assem-bly and 

 Unijunction Accelerator Switch 



Materials 



(1) 330 ohm resistor, V2 watt, 5% tolerance 



(1) unijunction transistor 



(1) 123AP transistor 



(1) 220 ohm resistor, V2 watt, 5% tolerance 



(1) 470 ohm resistor, V2 watt, 5% tolerance 



(1) circuit board 



(1) 500uf 0-25DC electrolytic capacitor 



(1) 4.7k ohm resistor, V2 watt, 5% tolerance 



(1) spool of 18 gauge stranded single-conductor wire 



Instructions (refer to Fig. 21) 



A) Assemble the electronic components comprising the uni- 

 junction assembly on the circuit board and solder into place. 



