In Case Of Difficulty; Voltage Chart - Heathkit SG-8 Assembly And Operation Manual

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VOLTAGE CHART
Pin 6 Pin Pin 7
Pin 8
Pin 4
Pin 9 TUBE Pin 1 Pin 2 Pin 3
•f
0 65
-6.
6.3 AC
6C4 65
NC 1
6.3 AC
6.3 AC 8 0 2.
0 12AU7
65
-2
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♦Dependent upon band.
NC - No connection.
alligator clip on the hot lead from the generator is then touched to the grid (through a .0 gfd
condenser) of the audio stage under test. This should produce an audible output of approximately
400 cycles if the stage is operating correctly and is connected to a good speaker.
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*-3 to-30i
Output Voltage: The RF signal strength going into the output control depends upon the strength
of oscillation of the 12AU7 oscillator. In all variable frequency oscillators the amplitude will
vary with the tuning condenser setting. With careful design the variation may be minimized .
In the Heathkit Signal Generator, the variation is kept down to a ratio of about 2 1/2 to 1 on each
band except band E, where the L/C (inductance to capacitance) ratio becomes sufficiently un ­
favorable that oscillation may drop off rapidly in strength when the condenser is near maxi ­
mum capacity. However, even on this band, the output of the SG-8 is in excess of 100,000 mi ­
crovolts which is more than sufficient for the average application in which this generator will
be used.
IN CASE OF DIFFICULTY
Recheck the entire wiring. Follow each lead and color it on the pictorial with a colored
pencil. If possible, have a friend recheck the wiring for you. Most cases of difficulty re ­
sult from wrong or reversed connections. In this unit, there is also the possibility of shorts
to the chassis occurring on some of the bare wire connections from the coils. These wires
should be carefully spaced away from the chassis when the instrument is assembled.
Check the test lead with an ohmmeter to be sure there are no shorts between the inner and
outer conductor caused by overheating during the soldering process.
If the wiring is found to be correct and the signal generator still refuses to work, try chang ­
ing tubes. It is possible that one of the tubes is defective.
Check the voltages. A voltage chart is included showing the normal voltage to be expected
at the pins of the tube sockets. These voltages were measured with an 11 megohm input
vacuum tube voltmeter. A normal variation of ±1 % is to be expected. With regular volt ­
meters, readings may be very much lower. All voltages are DC unless otherwise indicated .
If only one band on the signal generator is inoperative, it is very likely that tne coil associ ­
ated with that band has become damaged. An ohmmeter connected between the terminals of
the coil should show continuity. If it does not, one section of the winding is open.