TTI TG501, Руководство по обслуживанию

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Now slowly adjust VR18 and VR22 to remove these peaks. Check the distortion meter reading
which should now be less than 0.5%, typically 0.3%. If not, very slightly adjust the above 4 presets
to achieve this. (If the instrument fails to meet specification, check the following: amplitude, linearity
and symmetry of triangle wave at TP9; pre and output amplifiers.) Adjust VR20 to trim dc output of
the sinewave converter, measured on the oscilloscope or use a DVM connected to the 50 Ohm
output (TP17). Adjust VR21 to give 10.2V peak to peak into 50 Ohm.
Triangle amplitude, adjust VR25 to give 10.2V peak to peak into 50 Ohm.
Squarewave amplitude, ajust VR24 to give 10.2V peak to peak into 50 Ohm.
Servicing Notes
The white printing on the pcb also shows all the points which are top soldered. The circles
(teardrops) show track pins and the squares show which lead of a component is top soldered.
Insulating washers are fitted to IC22, Q32, Q34 and Q39. Heatsink compound is applied to
regulators IC22, Q32, Q34 and Q39 and between transistor pair Q20 and Q21.
To help with trouble shooting the power supply etc., an external current limited (500mA) power
supply of +/-17V can be used with its ground (0V) going to the TG501 ground (negative end of C50
or positive end of C51). The +17V supply is connected to the positive end of C50 and the -17V
supply is connected to the negative end of C51.
Typical current drain from the +/-17V supply with output at minimum is -200mA and +240mA.
Input power with 240V input, 90mA maximum.
This service manual specifically covers issue 5 pcbs. Pre issue 5 boards have the following
differences:
R35 100R was fitted in series with R36//C11 and not in the sinewave converter.
R142 was 4K7
pcb support brackets were not fitted.
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