Power Acoustik A3000db - DC on output while remote off

imraneesa · 2018-09-20 4:32 pm

Hi,

I fixed the above amp long time ago may be 2 months back. now he brought the amp back saying it pops the speakers while remote connection is taken off. when i checked there are good waveforms on the outputs. but when the remote signal is off dc coming on the speaker terminals. when the amp on no dc on speaker terminals. any suggestions where to look at. Thank you.

Best Regards
Imraneesa

Perry Babin · 2018-09-20 4:35 pm

Do the rails remain even (±) when driving a speaker?

Is the DC just a short pulse or constant with a speaker connected?

imraneesa · 2018-09-20 4:56 pm

yes the rails remaining even. DC is just a short pulse. when you remove the remote the dc just pulses and thats it.

Perry Babin · 2018-09-20 5:01 pm

Is the control voltage on the drive board switching properly? Delay to ground on start, instant release on remote off?

imraneesa · 2018-09-20 5:39 pm

voltage regulation optocoupler is having 5v instead 2.386v. and the tl431 ic have 1.7v between pin 1 and pin 2

imraneesa · 2018-09-20 6:46 pm

Perry Babin said:
Is the control voltage on the drive board switching properly? Delay to ground on start, instant release on remote off?

where to find control voltage on drive board?

Perry Babin · 2018-09-20 7:35 pm

Pin 6 from the RCA end of the driver board.

imraneesa · 2018-09-20 8:08 pm

Perry Babin said:
Pin 6 from the RCA end of the driver board.

Intially it has 4.8v without remote. all the delay time voltage start to increase and when the amp came on voltage gone zero volts. as soon as i removed the remote voltage immediately started to climb.

Perry Babin · 2018-09-20 8:56 pm

The control voltage should be near positive rail voltage between remote applied and the end of the mute delay. At the end of the mute delay (red-green LED switch), the control voltage will go to very near ground. When remote voltage is removed, the control voltage will immediately go back (not climb slowly) to positive rail voltage.

imraneesa · 2018-09-20 9:05 pm

when i apply remote it reaches 67v before the green led comes on. and when remote it removed it jumps to 45v and then goes down.

imraneesa · 2018-09-21 2:04 pm

Perry Babin said:
The control voltage should be near positive rail voltage between remote applied and the end of the mute delay. At the end of the mute delay (red-green LED switch), the control voltage will go to very near ground. When remote voltage is removed, the control voltage will immediately go back (not climb slowly) to positive rail voltage.

voltage regulator is working very good. i was using current limit resistor so voltage regulator was not coming on. now it is working good. and the control voltage is also there on the driver board. i am still getting a pulse on dc when remote is removed. when the amp is on delay and when it comes on everything works great except when you remove the remote it gives dc pulse.

Perry Babin · 2018-09-21 2:34 pm

Short the LED side of the opto-coupler used to switch the control voltage. Does the amp still pop?

imraneesa · 2018-09-21 3:15 pm

Perry Babin said:
Short the LED side of the opto-coupler used to switch the control voltage. Does the amp still pop?

No it did not pop after shorting the led in optocoupler.

MarioRestucci · 2018-09-21 5:11 pm

Mr. Babin, I apologize for the intrusion, I wanted to recommend checking Q113 (typically KTA1023) on the driver board (if the optocoupler works well), it may be short causing the perpetual D-class operation even when the amplifier is turning off ( when the remote signal is disconnected), where instead it should stop, as soon as the remote signal is disconnected.

imraneesa · 2018-09-21 5:30 pm

MarioRestucci said:
Mr. Babin, I apologize for the intrusion, I wanted to recommend checking Q113 (typically KTA1023) on the driver board (if the optocoupler works well), it may be short causing the perpetual D-class operation even when the amplifier is turning off ( when the remote signal is disconnected), where instead it should stop, as soon as the remote signal is disconnected.

q113 is fine.

Perry Babin · 2018-09-21 5:48 pm

On the scope, the voltage on the control pin should go IMMEDIATELY back to near rail voltage. The way you described it, it seems that it's going back slowly. That is a problem.

imraneesa · 2018-09-21 6:31 pm

Perry Babin said:
On the scope, the voltage on the control pin should go IMMEDIATELY back to near rail voltage. The way you described it, it seems that it's going back slowly. That is a problem.

Do you have any schematic to trace why it delaying. or can you give me some idea what to look at.

Perry Babin · 2018-09-22 2:22 am

Desolder the opto switching the control voltage and lift terminal 5 and reinstall the opto. Power the amp up connect a speaker and signal source. Using a screwdriver (insulated handle), short pad 5 to pin/pad 6. Does it go quietly into and out of muting?

imraneesa · 2018-09-22 2:10 pm

Perry Babin said:
Desolder the opto switching the control voltage and lift terminal 5 and reinstall the opto. Power the amp up connect a speaker and signal source. Using a screwdriver (insulated handle), short pad 5 to pin/pad 6. Does it go quietly into and out of muting?

yes it goes quietly into and out of muting. no problem.

Perry Babin · 2018-09-22 4:31 pm

Solder pin 5 back to the board (on top is OK) and after the amp comes out of muting, short pins 3 and 4. Does it go in and out of muting quietly?

Power Acoustik A3000db - DC on output while remote off

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