HP 5334B Service Manual page 178

8-397. Disassembly for Troubleshooting
8-398. To disassemble' the oscillator unit:
a. Remove three screws securing bottom cover to outer housing, and remove bottom cover.
b. Remove two screws securing pc edge connector to outer housing.
c. Remove foam sheet to expose oven controller circuit board.
CAUTION
Wih the cover and foam insulator removed, the thermal fuse cannot
protect the oven circuit from thermal runaway. Caution should be
used at all times.
If troubleshooting the oven controller, stop here and go to paragraph 8-400, Option 010 Oven Con-
troller Troubleshooting. Go to Step d only if the trouble is in the oscillator circuit.
WARNING
THE OSCILLATOR'S INTERNAL OVEN MASS TEMPERATURE MAY BE
AS HIGH AS 85°C (185°F). TO AVOID SERIOUS BURNS, DO NOT
REMOVE OSCILLATOR CIRCUITS AND/OR OVEN MASS ASSEMBLY
FROM THE OUTER CAN UNTIL THE OSCILLATOR HAS SUFFICIENTLY
COOLED (APPROXIMATELY ONE HOUR WITH BOTTOM COVER AND
FOAM INSULATOR REMOVED). THE OUTER HOUSING TEMPERA-
TURE IS NOT A RELIABLE INDICATION OF THE INTERNAL TEMPERA-
TURE.
d. Using a long, small diameter tool, remove the complete oscillator assembly by inserting the tool into
the tuning capacitor access hole (labeled FREQ. ADJ.) and gently pushing on the capacitor until the
circuit can be grasped and removed easily.
e. Using a pozidriv screwdriver, remove two screws securing heater transistors to the oven mass.
Remove washers and transistor insulators.
HP 5334B
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Service Manual
8-58