Wavetek 188 Manual page 31

Table 6-8. Symmetry
Indication: Waveform symmetry problem.
Check
If Faulty, Check
Set controls to initial positions (refer to paragraph 6.4).
If symmetry problem appears on х 1, x 10, x 100 ranges only, problem
may be R90 adjustment or go to table 6-9.
Perform steps 5 through 12 of table 6-7, then return to this table.
Verify RUN signal at cathode CR6 is approximately + 3.5V.
Verify U6 pin 4 and U6 pin 15 vary from approximately — 10 to — 15V as
dial is rotated from 4.0 to .004.
Verify amplitude of ЗОВ signal at cathode СВІТО is approximately + 2V.
Check U5, CR6.
Check for normal operation.
a. R49 adjustment.
b. R45 adjustment.
Go to table 6-10.
U1, U6, R52, R53.
a. Q7 circuit.
b. U7 circuit.
с. +5V supply.
Table 6-9. Capacitance Multiplier
Indication: Problem on bottom frequency ranges only.
Check
Set controls to initial positions (refer to paragraph 6.4).
Check for 0 Мас at U11 pins 2 and 6.
Check for approximately O Vdc at U11 pin 12.
Check for 0 Мас +5 mV at 011 pin 10.
Select х 100 range; check U11 pin 10 for heavy oscillations.
Ensure that R93 and R94 are shorted in the x 100 range.
Corrective Procedure
Check for normal operation
on x 1K range.
SW2 - SWA.
U11 circuitry.
a. R90 adjustment.
b. U11 circuitry.
C46, 911.
U11 circuitry.
SWA, U11 circuitry.
SWA.
6-7