TTI TG501, Руководство по обслуживанию

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Sinewave amplitude - VR21
Squarewave amplitude - VR24
Triangle wave amplitude - VR25
DC offset of preamplifier - VR26
Output amplifier quiescent operating current - VR32 and VR33
Output amplifier dc offset - VR31
Output amplifier bias compensation - VR28
Output amplifier LF gain - VR30
+15Vrail - VR34
For best results the above adjustments should be carried out in the following manner:
After the instrument has warmed up the case upper is removed to make any adjustments, which
should be done in a draft free environment.
Adjust VR34 for +15.0V +/-100mV at TP12
Check -15V rail is /-2% of the +15V rail at TP18
Check +10V rail is +10.2 +/-400mV at TP19
Check -10V rail is /-2% of the +10V rail at TP21
Check +5V rail is 5.0V +/-0.25V
Check -5V rail is -5.0V +/-0.25V
Select: Run, 1k range, dial at 5.0, dc offset out, squarewave, 0dB
Offset nulling of ICs 1 to 6 is critical for correct operation of the instrument. Gold plated test pins are
provided and a gold plated 2 way header on the end of the leads to the DVM is recommended to
make a good connection and help to avoid thermal e.m.f.s.
IC TP Adjust DVM Reading
1 13 VR4 <40uV
2 1 VR5 <40uV
3 2 VR6 <40uV
4 3 VR7 <40uV
5 4 VR10 <40uV
6 5 VR12 <40uV
8 6 VR13 <100uV
9 7 VR14 <100uV
12 10 VR16 <100uV
Nulling of the triangle amplifier is achieved by shorting its input (TP11) and adjusting VR17 to give
<2mV at TP9.
To null the pre-amplifier, deselect the waveform output by releasing the 3 function buttons. Connect
a DVM to the right hand leg of the amplitude control (VR27) and adjust VR26 for <3mV.
Output stage adjustment must be carried out with great care to avoid circuit damage. Adjustment is
easiest with 2 voltmeters, one connected to TP15 and the other to TP14. With only one meter
available, alternately monitor the 2 test points. With no output waveform selected and the amplitude
control at minimum, slowly adjust VR32 and VR33 for 13.4V to 13.5V at the two test points. Note
14