Ecler PAM2000, Service Manual

Page: 67 / 107

PROFESSIONAL PAM SERIES - TESTING RULES
PRELIMINARY
GROUND LINK Testing.
- Verify that when the switch is at the ON position there is continuity between the chassis ground and the
speakers ground terminal and that the opposite happens at the OFF position. Leave it at ON.
- Put the power amplifier in stereo mode.
- We will need a 4000VA variac for our test purposes.
- Take off one of the fuses of the module in which the testing is being made and connect an ammeter (10A DC
scale) in its place.
- Put the oscilloscope probe between TP-GND.
SET UP
- Unplug the fuses of the module that we are NOT setting up.
- Connect the power amplifier mains cable to the output of the variac. Set the variac output at 0V.
- Switch the power amplifier on with no load or signal. Turn the variac up progressively step by step until 220V.
While mains voltage is growing up make sure the module's current does never exceed 0.8A. Once the circuit is
stable make sure the current is 480mA/400mA respectively for PAM2600/ PAM2000 and the symmetry
(measured up with the oscilloscope probe) is
# 50mV. If your figures do not match these numbers adjust
CURRENT (5K) and SYMMETRY (470
Ω
) untill you get the above mentioned numbers.
- Test the operational amplifier power supply ( " 18V) " 1V.
- Put the fuse back in its place into the module (with the power amplifier turned off) and repeat the same
procedure for the other channel.
CROSS DISTORTION
By using a signal generator introduce a level of 100mV RMS at 1kHz and make sure there is no cross
distortion at the output (attenuators at 0dB position).
MOSFETS CONDUCTION
By using a signal generator introduce a level of 0.5V at 1kHz and load the amplifier with 4
Ω
.Check that all
MOSFETs are conducting approximately the same current level (measure this current with the oscilloscope probe
by palcing it on the 0,22
Ω
source resistances).The maximum conduction difference between MOSFETs should be
100mV. When making this test be sure the oscilloscope ground is not connected to any other place of the circuit
when making the reading; just to the 0,22
Ω
resistance.If you do not follow this rule you could produce a
shortcircuit between two points of the circuit and therefore a very important damage.
POWER
- Verify the amplifier's power at 8 and 4
Ω
.
- Maintain the mains voltage at 220V by means of the variac.
- Check that your own figures match the following at close-to-clip point:
PAM2600 PAM2000
Vin
.
1VRMS/Vo 4
Ω
$ 70 Vrms 60.5 Vrms
Vin . 1VRMS/Vo 8
Ω
$
81 Vrms 68 Vrms
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