HP 8642A Operating Manual page 350

Model S642A/B
Service
CHANGES
2S26A and above
2613A and above
On the schematic:
* In 5 MHz OSCILLATOR, change the power supply to U2 pin 4
from+5V(Fl)to+5V(F3).
On the Component Locator:
* E£2 ~ Add R52 between U4 and U33.
In Component Coordinates:
* RS2 - AddR52B,l,
On the schematic:
* R52 - In 5 MHz OSCILLATOR, add R52 immediately off the
output of U4 pin 14, in the series path before the first node.
* In the upper left portion of the schematic change the A3 part
number to 0S642-60224.
rev!0MAR86
SS4
8F-102.1