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4.

Crossover distortion in output

Refer to Figure A above and note the character of crossover distortion. This is caused by
both halves of the output stage (Q1, Q2 on positive side, and Q13, Q12 on the negative
side) being turned off right around crossover (crossover from positive drive to negative
drive). This actually takes a small chunk (sometimes only visible in distortion waveform)
out of the center of the output waveform. This also causes some harmonic distortion (Note
the curved portions of the “Distortion Waveform”). Remove input signal to amp and mea-
sure DC voltage across emitters of Q1 and Q13. Bias adjustment, VR1, should allow
adjustment from zero volts to well over 10mV. If not proceed to “Bias Reference Test”.

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Содержание EON Power10

Страница 1: ...roduct repaired with out JBL specified components may not meet the factory specifications The product war ranty may be voided by a repair using unapproved JBL components Test Equipment 1 Audio Precision System One or Distortion Analyzer Function Generator 2 20MHz Oscilloscope 3 Desoldering Equipment 4 Digital Multimeter 5 High Power Load Bank 6 Variac The complexity of the product under repair req...

Страница 2: ...it is available for the M115 8 woofer Entire driver should be replaced 124 67001 00X NOTE To recone the EON woofers it is not necessary to disassemble the enclosure The woofer can be reconed from the front Tools and Supplies The following items will be required to properly recone the speaker Screwdriver Long Nose Pliers Masking Tape MEK Utility Knife Teflon or Orange Stick Gap Gauges 0 089 15 mode...

Страница 3: ...compliance land and spider land with MEK or acetone 7 Remove tape from gap and clean magnet gap with masking tape and with MEK and a rag 8 Unpack recone kit and inspect for damage 9 Verify that the voice coil impedance is correct for the model under repair 8 ohm voice coils have a blue mark near the leads and are used in the passive models ONLY 10 Place Mylar tube inside the voice coil 11 Test fit...

Страница 4: ...Test Station 7 Air Gun and Safety Glasses Procedure 1 Record Model number Serial number Date code and compliant for warranty information 2 Lay the enclosure face down on a soft clean surface to avoid damage to the grille The woofer or bottom of the product should be towards the front of the service table 3 Using a Phillips head screwdriver remove the 2 screws holding the handle and remove the hand...

Страница 5: ...800Hz If no buzzes are detected then test at 2V from 1 500 Hz to 20 kHz for full range operation and audio clarity It will be necessary to lift the baffle to expose the horn so listening tests can be performed accurately 15 Reconnect the high frequency lead wires to the appropriate terminal on the compres sion driver The terminals are polarized so they will fit only one way Reconnect the trans for...

Страница 6: ...201 Verify resistance from pin 2 to pin 1 of U202 pin 3 of U202 to ground 10K If not check for opens and shorts around U202 5 Rotate Volume control counter clockwise while monitoring pin 1 of P204 Voltage should gradually decrease to zero If the level is intermittent or control does not attenuate replace defective P201 E Line Amp Frequency Response Test Advance volume fully clockwise and adjust fo...

Страница 7: ...evel for 20V P P on pin 1 of P204 Verify that Peak LED D203 as well as signal LED D201 are on Turn volume control down and verify that Peak indicator turns off A Initial Setup The easiest way to drive the EON Power15 Main Board is to connect it to a known good EON Power15 Input Board Interconnect both boards using a 7 pin cable assembly Place the input board in Line mode S201 out Advance volume co...

Страница 8: ...t to the amp is not clipped The amp input can be measured at the junction of R22 and C18 With 60V P P at the amp output there should be around 1 9V p P at the input to the amp If one or more of the above tests fails proceed to Low Frequency Power Amp Test Adjust oscillator for 1 9V p P at pin 1 of U2 Verify voltage at input to the filter pin 1 of J3 is about 3 5V P P If not proceed to Low Frequenc...

Страница 9: ...ency Power Amp Test F Supply Test 15V Supply Test Slowly ramp up Variac never allowing the supplies to exceed 16V Measure 15V and 15V supplies Both should be the correct value 5V If a supply is very close to ground potential Less than 100mV check for 1 shorts on the 15V supplies references Z3 or Z4 2 open or incorrect reference bias sources R52 and R65 3 open series pass devices Q18 and Q19 4 39V ...

Страница 10: ... to zero check for 1 collector to emitter short on Q17 2 incorrect value R49 3 shorted TS1 Thermostat should be open when cold and will close at 80 degrees C 4 reversed or shorted Z2 If voltage ramps up higher than 10V check for open or incorrect value Z2 and for an open Q16 from base to emitter Interrupt power while monitoring collector of Q17 The voltage should quickly fall close to zero volts I...

Страница 11: ...any greater than 2 5VDC Measure resistance of R9 and R21 the correct value is 243 ohms If R9 or R21 value incorrect or if the voltage across these parts is excessive proceed to Voltage Amp Test If R9 and R21 testing doesn t uncover a problem and shorting C12 does bring the power consumption to normal proceed to Bias Reference Test Remove jumper across C12 If the output voltage is offset LF test po...

Страница 12: ...ossover from positive drive to negative drive This actually takes a small chunk sometimes only visible in distortion waveform out of the center of the output waveform This also causes some harmonic distortion Note the curved portions of the Distortion Waveform Remove input signal to amp and mea sure DC voltage across emitters of Q1 and Q13 Bias adjustment VR1 should allow adjustment from zero volt...

Страница 13: ...the characteristics of the waveform and then probe on both sides of C12 C12 is across the input to the current amp If the waveform visibly appears almost identical Same P P voltage same waveform shape then the problem lies in the voltage amp Proceed to Voltage Amp Test If there is much difference between the output waveform and the waveforms measured at C12 there is probably a problem in the curre...

Страница 14: ...es the output bias current and keeps it constant with temperature a Excessive power pulled from AC line This is due to excessive voltage across reference The range measure across C12 should be 1 7V to 2 8V If not check R13 VR1 R14 and Q5 b Crossover distortion in output waveform This is due to inadequate voltage across reference The range measure across C12 should be 1 7V to 2 8V If not check R13 ...

Страница 15: ...erify that voltage across R5 equals 870mV 20 If incorrect check Q4 for open or shorted elements Verify that the voltage at the emitter of Q3 is 6V If incorrect check Q3 and Q4 for shorts and opens Verify that the voltage across R29 and R5 are the same 10 If not check values of R5 and R29 243 ohms Verify that D9 isn t open shorted or reversed If the above checked OK verify value of R21 243 ohms and...

Страница 16: ...function of the first filter section R63 R64 and C37 when this section is operating properly Sweep the oscillator frequency and note if the readings are reasonably close to the values indicated in the plot above 15 For example with a filter that operates normally the output will be 2 3V P P at 20Hz 2V P P at 500Hz 850mV P P at 2kHz 300mV P P at 6kHz and 90mV P P at 20kHz The first section is a low...

Страница 17: ...on of the filter The second section is a moderate Q Q equals about 2 high pass filter at 55Hz Because of the moderate Q the filter actually peaks The 55Hz Peak Verify the peak frequency 55Hz and the peak voltage 5 1V P P Also verify voltages at 20Hz 100Hz and 1kHz and 20kHz If the response is incorrect check values of C35 C37 and R59 and R60 After obtaining proper response proceed to following sec...

Страница 18: ...response at the output of the third section of the filter The third section is a low Q Q equals about 7 high pass filter at 33Hz Verify the peak frequency 55Hz and the peak voltage 5 1V P P Also verify voltages at 20Hz 30Hz and 40Hz If the response is incorrect check values of C29 C30 C34 R56 and R57 After obtaining proper response proceed to following section ...

Страница 19: ...ourth section is a moderate Q Q is a little more than 1 low pass filter at 1 4Hz Verify voltages at 100Hz 1kHz 2kHz and 4kHz If the response is incorrect check values of R53 R55 C28 and C33 Reattach lifted lead of C18 Bias Set Procedure The following steps are necessary to set the bias on the Power15 amplifier module PCB 510 00007 XX rev any 1 Connect a 4 ohm load 250 watts to the red and black le...

Страница 20: ...ntial If not close check for shorts surrounding pin 10 If no shorts are found replace U1 Verify that pin 9 reflects the output offset polarity The offset should be much greater than 1V If not look for shorts surrounding pin 9 and verify values of R38 R40 and C25 If no problem found replace U1 2 No output from the amp when driven Verify input to the amp on pin 10 If no signal is present verify that...

Страница 21: ... pin 1 of J3 The curve below this line represents the transfer function of the first filter section R61 R71 and C44 when this section is operating properly Sweep the oscillator frequency and note if the readings are reasonably close to the values indicated in the plot above 15 For example with a filter that operates normally the output will be 3 3V P P at 20kHz 3V P P at 7kHz 1 5V P P at 2kHz 350m...

Страница 22: ... curve represents the response at the output of the second section of the filter The second section is a moderate Q Q equals about 2 high pass filter at 1 9kHz Be cause of the higher Q the filter actually peaks The 2 1kHz Peak Verify the peak frequency 2 1kHz and the peak voltage 3 2V P P Also verify voltages at 40kHz 20kHz 1kHz and 600Hz ...

Страница 23: ...High Frequency Response EON Power15 and EON15P 1 230 33 ...

Страница 24: ...Low Frequency Response EON Power15 and EON15P 1 230 34 ...

Страница 25: ...e from pin 2 to pin 1 of U2 pin 3 of U2 to ground 3 2k if not check for opened and or shorted traces around U2 5 Rotate volume control counter clockwise while monitoring voltage at the junction of pin 2 of R16 and C10 Voltage should gradually decrease to zero If level is intermittent or control does not attenuate replace defective pot R16 D Common Mode Rejection Test Set Generator output drive to ...

Страница 26: ...d Interconnect both boards using a 6 pin cable assembly Advance Volume control on input board R16 fully clockwise Attach power transformer to J5 Adjust bias control R17 fully counter clockwise if at all uncertain about the bias adjustment being correct Connect the output to a 4ohm load Connect generator output to input board s XLR connector Generator output should be turned off B Main Loop Test Mo...

Страница 27: ... 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 a...

Страница 28: ...for possible shorts in the areas where these parts are All the above parts form the Current Amplifier Providing current gain Everything from Q10 Q12 and before form the Voltage Amplifier Providing voltage gain b If output voltage is at ground potential test point 4 TP4 and output leg is not shorted there could be a problem with the bias reference Check transistor Q5 2SD1763A make sure base is not ...

Страница 29: ...e current amp Q3 Q1 Q7 and Q8 the bias reference needs to have around 2 4V 4 drops across it to turn on all four transistors in the current amplifier The range of adjustment is very small Between 1 7V and 2 8V when R17 adjusted from stop to stop The reason the adjustment range is small is because very little change in voltage across the reference produces radical bias current changes in the output...

Страница 30: ...Low Frequency Response EON PowerSub 40 ...

Страница 31: ... 400Hz 2 Verify that voltage at output pin 1 of J1 800mV P P 100mV 3 Verify presence of 400mV P P 50mV at pin 1 of U1 4 Remove oscillator connection to XLR input Verify resistance from pin 2 of J2 to pin 3 of U1 Pin 3 of J2 to pin 3 of U1 24 23K If not check for shorted sections of SW1 Verify resistance from pin 2 to pin 1 of U1 pin 3 of U1 to ground 10K If not check for opens and shorts around U1...

Страница 32: ... a 7 pin cable assembly Place the input board in Line mode SW1 out Advance volume control on input board R25 fully clockwise Attach power transformer to J7 Connect the low frequency output to a 4 ohm load and the high frequency output to a 8 ohm load Connect generator output to input board s XLR connector Generator should be turned off B Main Test Loop Monitor 15V supply while slowly advancing Var...

Страница 33: ...one or more of the above tests fails proceed to High and Low Frequency Power Amp Test If the oscillator is adjusted for 4 9V P P at pin 7 of U4 the voltage at the input to the filter pin 1 of J6 should be about 7 7V P P If not check high frequency filter IC s U3B and U4B E Excessive Line Power Test Verify correct polarity and that none the following parts are not shorted C41 C42 main filters and D...

Страница 34: ...ls the power consumption should go to normal idle level less than 40W if the load is removed If it does not check for shorting from the output pin pin 3 to either the 31V or 31V supplies If not shorted replace U1 or U2 Depending on which one failed Verify that the input to the amp pin 10 of both U2 or U1 is close to ground potential If not close check for shorts surrounding pin 10 If no shorts are...

Страница 35: ...High Frequency Response EON Power10 45 ...

Страница 36: ...Low Frequency Response EON Power10 46 ...

Страница 37: ...annel 1 Do not plug anything to the Patch nor to the Phone Jacks Adjust volume control R47 Master and R48 Channel 1 fully clockwise and all EQ controls flat at center detented point Verify that the voltage at pin 1 of J1 is 1 28V 100mV Verify 215mV 50mV on pin 1 of U1A and pin 1 of U3A Meter Feed Verify 430mV 50mV on pin 7 of U1B Verify 0 5V on pin 1 and 7 of U7 pin 1 and 7 of U8 Verify 400mV 25mV...

Страница 38: ...the output at pin 1 of J1 is approximately 9 3 dBu Turn High Mid Frequency EQ control fully clockwise and verify that pin 1 of J1 is now approximately 21 2 dBu Turn same knob fully counter clockwise and verify that pin 1 of J1 has now decreased to 2 8 dBu If none of the above is true check U8B C45 C56 R74 R63 R59 and all traces solder around them If all the above is true set knob back to center de...

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