ELTRA CS-800, Manual

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3.4.7.6 Loud buzzing sound when the generator turns on
If during integration (combustion period) the high voltage transformer is making
exceptionally loud buzzing sound when the generator turns on, also when running
the furnace empty still the loud buzzing appears, this means that obviously for
some reason, the triggering of the triac has changed.
If you are sure that the noise appears only during integration period (combustion
period) then the problem could be in the generator. The unusually loud noise could
be due to current limitation by phase angle control.
The oscillator tube may not be oscillating due to a tube fault so that it takes a very
high DC current causing the current limit circuit to reduce the phase angle. Replace
the tube. This is also the easiest thing to try so that it can be done by the customer.
NOTICE
The oscillator tube can be damaged due to overheating if for some other reason
the new tube may not be able to oscillate. For testing after installing the new tube,
put crucible with sample and accelerators into the furnace like you use to do with
every normal analysis. After starting analysis watch carefully the furnace to see the
light of the burning sample/accelerators. If a couple of seconds after generator start
(transformer noise, base lines for peak on the PC screen) there is no combustion
to see in the furnace then STOP the generator by clicking STOP on the screen.
NOTICE
When testing for induction power, always test with closed furnace.
NOTICE
When looking to find out whether there is combustion or not, STOP the analysis
cycle about 3 seconds after it started. If there are oscillations, after 3 seconds the
sample (steel or iron chips) will have visible signs of starting burning. But if you wait
up to the end of the analysis cycle in order to check whether there was
combustion, it could be already too late for the tube due to overheating.
When there are no oscillations, the tube takes a high DC current, so that after
several seconds, the anode of the tube starts glowing from the lower end. This can
be visible when the environment is not bright or it is dark.
It is practically not possible to do any measurements on the generator due to very
high voltage and due to high frequency in the oscillator (in case of functioning). So
we have to solve the problems by looking and trying.
One reason could be the resistor (8) having a short circuit. Normally its resistance
has the value of 200K.
One more possibility is a faulty capacitor. Check the capacitors, mainly the one on
top (7) of the oscillator circuit which is connecting the anode of the tube with the
oscillator circuit. Check also the grid capacitor (6) which is placed underneath the
oscillator chassis. Try to find out whether they are broken by applying a reasonable
force on them to see whether they are still in one piece. If the analyzer is relatively
old and these capacitors are in silicon sleeves, the chance that one of them is
faulty, is relatively high. If these capacitors are in brown plastic, it is less likely that
they are faulty, according to our experience.
Check also the other, bigger capacitors (9), (10) and (11) however if one of them
was faulty, most probably the fuses would blow.
Pos : 5. 13 /0020 Übersc hrift en/ELTRA 1.1 Übersc hrift en/11 Bad c ombus tion ELTR A @ 6\ mod_1368608656440_9.doc x @ 40248 @ 22 @ 1
3.5
18B
Bad combustion
Pos : 5. 14 /0010 ELTR A/ 0015 s ervic e_ins truc tions/C S-800_Ser vic e/ 0015 F ehl er/ 0135 Modul Schl ec hte Verbr ennung - Bad combusti on ELTRA @ 6\ mod_1377688600953_9. doc x @ 46555 @ 2 @ 1
In most cases the reasons for bad combustion are:
– Problems with the flow
– The Generator (oscillator) tube is not powerful enough anymore. Normally,
this does not occur suddenly. It is rather a long process.
(Part number 77210)