39
Fig. 18: Measurements - high voltage transformer
Once there is voltage on the transformer the triac must be OK. A relatively low
voltage on the transformer could be a result of too high current so that the HF-42
board reduces the phase angle. IF so there is most probably a faulty component in
the oscillator circuit preventing it from oscillating so that the oscillator tube takes a
high DC current.
NOTICE
This can damage the tube. Therefore when you start for testing whether there is
combustion keep your finger on the STOP button. If the sample does not start
burning about 3 seconds after the generator starts, then immediately stop the
analysis.
One thing that will give further evidence is the current taken by the analyzer from
the mains power.
If the current goes up to a level of about 10A, then a faulty component prevents
oscillations so that the tube takes all this power causing overheating of the tube
within several seconds.
If the current does not increase, it means that the generator does not take power,
for example due to a broken grid resistor.
In case the transformer has 210 V AC on the primary coil and there is still no
combustion, check the windings of the transformer as follows:
• Switch off the analyzer and disconnect the main power plug.
• Measure the resistance of the primary coil.
– It must be extremely low, about 0.8 Ohms between the
screws labeled 0 and 270.
• Measure the resistance of the secondary coil between the two screws on the
ceramic insulators where the wires of the rectifier are connected.
– The resistance is approximately 322 Ohms.
3.4.7.5 The rectifier could also be faulty
Checking the high frequency generator
DANGER
Mortal danger from electric shock
Exposed power contacts - High Voltage
Never try to measure the voltage here!
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