Tektronix 2A60 Instrument Reference Book page 40

Type 60 (con 'd)
INPUT AMPLIFIER FILAMENT
VOLT AGE SOUR CE CHANGED
TO ELIMINATE VERTICAL
TRACE SHIFT
See SQB
M3591
Effective Prod s/n 432 Usable in field instruments s/n 101-431
FRONT PANEL SYMPTOM: Vertical trace shift with changes in line voltage.
PROBLEM: The filaments of V 434 and V 444 were connected across the 6. 3 V AC winding of
the indicators power transformer via the interconnecting plug.
PRODUCTION CHANGE: The filaments of V434 and V444 were connected in series across
the -12V DC regulated power supply. This was accomplished by changing the cable
harness. Hum balance potentiometer R493, for V434 and V444, was removed
because is was no longer necessary. The chassis was changed to eliminate the
R493 potentiometer hole and silk screen markings.
Parts Removed:
R493
Parts Added:
Cable, harness
Pot, 25on
Chassis
Cable, harness
Chassis
*Wire, #22 solid,
*Wire, #22 solid,
*Wire, #22 solid,
INSTALLATION INSTRUCTIONS:
9" black
l l" black -brown -red
19" black-brown -orange
Parts Required: See 'Parts Added' with asterisks.
Installation Procedure:
a) Unsolder the two white-blue-yellow wires from Pin 4 of V434.
179-0458-00
311-0194-00
441-0333-00
179-0547-00
441-0391-00
175-0514-00
175-0514-00
175-0514-00
b) Unsolder the white-blue-yellow wire from Pin 5 of V463, that connected to Pin 4 of V434.
Cut the three white- blue -yellow wires, unsoldered in Steps a and b, off close to the cable
harness.
c) Unsolder the white-blue-orange wire that connects Pin 4 of V463 to Pin 3 of V434, from
Pin 4 of V 463.
d) Unsolder the two white-blue-orange wires from Pin 3 of V434.
Cut the three white-blue-orange wires ,unsoldered in Steps c and d,,off close to the cable
harness.
e) Unsolder the white-yellow wire from Pin 4 of V 444, and the white-orange wire from Pin 3
of V444, and cut them off close to the cable harness.
Using the wire called out in "Parts Required:" above, wire the filaments of V 434 and V 444
across Pins 5 and 16 of the interconnecting plug as shown in the drawing on following
page.
NOTE: The Hum Bal. pot is left in the circuit in parallel with the filaments of V463, V474 and
V 483; however, since it is no longer across the input tube filaments it will have little or
no effect on operation.
continued
Page 4
60/2A60 MODIFICATION SUMMARY 3-11-68