37
4.
Check for the presence of +/– 95V at test points 2 and 5 (TP2, TP5). If low or non-
existent refer to “+/– 95V Supply Test”.
5.
Verify that “Mute Line” voltage at pin 7 of IC U1B is at 15V. Remove power to unit and
verify that mute line immediately goes low (–15V). Re-power board and verify that mute
line initially goes high. If any of the above is not true refer to “Amplifier Muting Test”.
C) Confirmation of Low Frequency Chain
Turn Generator off, verify 4mV of bias voltage at test point 3 (TP3). Adjust bias pot, R17,
for 4mV DC +/– 300uV (20mA) if required. Measure at the output of the amplifier (J1, red
lead) and confirm less than +/– 50mV of offset. Turn on Generator and adjust frequency
to 100Hz. Adjust oscillator amplitude to obtain 60V P/P at amp output. The waveform
should be a nice clean sine wave. The amp will begin to clip at around 87V P/P. If the amp
prematurely clips, verify that the input to the amp is not clipped. The amp input can be
measured at the junction of R35 and C20. With 60V P/P at the amp output there should be
around 1.7V P/P at the input to the amp. If one or more of the above tests fails, proceed to
“Power Amp Test”.
Adjust oscillator for 1.7V P/P at pin 1 of U1A. Verify that the voltage at the input to the filter,
pin 1 of J3, is about 2.7V P/P. If not, check for shorts or open circuits around filter IC’s
(U2A, U2B and U1A).
E) Excessive
Line
Power
Test
Verify the correct polarity and that none of the following parts are shorted:
C4, C10 (Main Filters), D13, D14 (Low Frequency Power Amp), D9 - D12, C11, C13, C3,
C12 (+/– 95V Doublers). Verify that no section of BR1 (Main Bridge) is shorted. Verify that the
+15V and –15V supplies are not shorted. Return to “Main Test Loop” when fault fixed.
F) Supply Test
+/– 15V Supply Test
Slowly ramp up Variac, never allowing the supplies to /– 16V. M15V and
–15V supplies. Both should be the correct value +/– .5V.
If supply is very close to ground potential (Less than +/– 100mV) or out of spec check for:
shorts on the +/– 15V supplies; for shorted references D1 or D4; for open or incorrect refer-
ence bias sources R12 and R19; for open series pass devices Q4 and Q6; for proper polarity
and value of C5 and C8; for excessive current being pulled (Do U1 and U2 run hot?).
+/– 48V Supply Test
Look for open traces between main bridge, BR1 and main filter capacitors, C4 C10. Look for
open traces between BR1 and power input connector, J5. Verify that BR1 is not open.
Return to “Main Loop Test” after fault found.
+/– 95V Supply Test
Check for correct value of R31 and R29 (3.24k) and verify 1.4V DC across them when board
is powered. Check for correct values of R30, R24 (464) and R23, R7 (150 ohms) and
Summary of Contents for EON15
Page 23: ...High Frequency Response EON Power15 and EON15P 1 230 33...
Page 24: ...Low Frequency Response EON Power15 and EON15P 1 230 34...
Page 30: ...Low Frequency Response EON PowerSub 40...
Page 35: ...High Frequency Response EON Power10 45...
