Purchased this amp a couple weeks ago.
Arrived with fake irfb4115s (reworked). Rdson of those parts was in the 170mOhm range. Also bridges we're blown, irs20957s chips likely bad, and some rc filter damaged.
I have legit irfb4115s in, new bridges and all else patched up.
The amp has a couple issues with starting and running above 14v though.
It takes considerable time to start, the power supply pulses, LEDs all blink, and rail caps slowly charge, it starts eventually. I removed the rail caps and they measure ok. They are back in now of course, didn't run amp with them out.
If I get it started and run it over 14v, the power supply waveform goes from good looking to a narrow high amplitude pulse and current draw decreases from 1.3A to about .7A and bounces around. Rail voltage remains ok, but is clearly in unhappy state. 7524 driver chip becomes quite hot.
Was considering ordering driver chips but the waveforms look the same on input and output when acting up.
Any ideas?
Thanks
Arrived with fake irfb4115s (reworked). Rdson of those parts was in the 170mOhm range. Also bridges we're blown, irs20957s chips likely bad, and some rc filter damaged.
I have legit irfb4115s in, new bridges and all else patched up.
The amp has a couple issues with starting and running above 14v though.
It takes considerable time to start, the power supply pulses, LEDs all blink, and rail caps slowly charge, it starts eventually. I removed the rail caps and they measure ok. They are back in now of course, didn't run amp with them out.
If I get it started and run it over 14v, the power supply waveform goes from good looking to a narrow high amplitude pulse and current draw decreases from 1.3A to about .7A and bounces around. Rail voltage remains ok, but is clearly in unhappy state. 7524 driver chip becomes quite hot.
Was considering ordering driver chips but the waveforms look the same on input and output when acting up.
Any ideas?
Thanks
Attachments
Are you sure that the amplitude increases when the pulse width decreases?
Is the change in pulse width abrupt or smooth?
What's driving the 7524?
Is the change in pulse width abrupt or smooth?
What's driving the 7524?
The microcontroller is driving the driver chip.
Shots of ps gate and 14.1v and 13.1v input. I guess amplitude didn't go up much in fact.
It abruptly changes.
I'm guessing the slow to start issue and the 14v issue are related, but can chase this part first. 🙂
Thanks!
Shots of ps gate and 14.1v and 13.1v input. I guess amplitude didn't go up much in fact.
It abruptly changes.
I'm guessing the slow to start issue and the 14v issue are related, but can chase this part first. 🙂
Thanks!
Attachments
This is how the microcontroller regulates the rail voltage and isn't a problem.
Make a note of the DC voltages on the MCU when the amp refuses to power up and again when the amp is functioning to determine which input is causing the startup problem.
Make a note of the DC voltages on the MCU when the amp refuses to power up and again when the amp is functioning to determine which input is causing the startup problem.
Poked around for awhile figuring out micro pinout. Figure this will be semi useful for these Brazilian cheapo amps.
Pin1 buffered remote turn on in to micro
Pin2 led
Pin6 driver out
Pin11 measures gate switching on outputs. Output gate to 1k to cap to small diode bridge to micro.
pin12 led
pin13 led
pin14 rail voltage measurement 22k/1k
Pin16 driver out
pin 17 through diode to irs20957 pin2 mute
pin20 gnd
Focusing on pins 11 and 14: 11 goes from 0 to 5v once it's alive and output gates are switching. Pin 14 slowly rises with each power supply pulse but is about .68v when alive (10.8v supply).
Nothing is getting unusually warm once alive, amp is out of chassis, but it seems like something is holding the rail voltage down. It takes quite awhile to turn on while the leds cycle.
Pin1 buffered remote turn on in to micro
Pin2 led
Pin6 driver out
Pin11 measures gate switching on outputs. Output gate to 1k to cap to small diode bridge to micro.
pin12 led
pin13 led
pin14 rail voltage measurement 22k/1k
Pin16 driver out
pin 17 through diode to irs20957 pin2 mute
pin20 gnd
Focusing on pins 11 and 14: 11 goes from 0 to 5v once it's alive and output gates are switching. Pin 14 slowly rises with each power supply pulse but is about .68v when alive (10.8v supply).
Nothing is getting unusually warm once alive, amp is out of chassis, but it seems like something is holding the rail voltage down. It takes quite awhile to turn on while the leds cycle.
Last edited:
I am not sure, but i think output fets are not 4115 for this amp.
Since they use H1 on the power supply side, i d expect to see H8s on the audio side.
Since they use H1 on the power supply side, i d expect to see H8s on the audio side.
I believe H6 is what they ship with. It came with fake 4115s in it.
I have a few options here, could try irfb4321 or irfb4227.
I have a few options here, could try irfb4321 or irfb4227.
What do you mean by:
Pin 14 slowly rises with each power supply pulse
Is the supply surging, on and off or are you referring to the individual 26kHz pulses?
Pin 14 slowly rises with each power supply pulse
Is the supply surging, on and off or are you referring to the individual 26kHz pulses?
Pin 14 is a voltage divider back to the micro that measures rail voltage I believe. It has a large voltage divider. I think once it hits a certain level the micro will stop pulsing and turn on and stay on?
Is the 5v input to the MCU within a few % of 5v?
Is the 12v supply voltage a steady 12v?
Are any pins other than the rail feedback pulsing with the supply surging?
Is the 12v supply voltage a steady 12v?
Are any pins other than the rail feedback pulsing with the supply surging?
Correction, 112k(100k+12k)/1k for pin 14 divider. Duh.
I actually have a couple sundown Brazilians here too to compare with. Pin1 5v input bounces around 4.8v while booting on this amp and on a good sundown. They do similar things, only the db amp goes through many many pulses and takes about 20sec to boot, sundown amps are in 1-3seconds.
The 12v supply I'm feeding the amps is from a linear supply. Actually 10.8v since it takes a bit longer to charge so I can debug longer before discharging caps.
Quite a few pins pulse when the supply pulses. Pin 6 and 16 of course. Pin17 pulses half a volt up when power supply surges. Pin11 pulses with surge. 14 rises a bit with each surge.
Looks like pin3 also goes to irs20957s mute. Pin3 has a 1k pulldown on it, then to a 1k to a diode to irs pin2. Pin17 has a 10k straight to a diode to the irs. Cathodes are on irs side. Not really grasping what this is doing.
Also pin 18 comes from a 10k 2.2k divider from +12.
I actually have a couple sundown Brazilians here too to compare with. Pin1 5v input bounces around 4.8v while booting on this amp and on a good sundown. They do similar things, only the db amp goes through many many pulses and takes about 20sec to boot, sundown amps are in 1-3seconds.
The 12v supply I'm feeding the amps is from a linear supply. Actually 10.8v since it takes a bit longer to charge so I can debug longer before discharging caps.
Quite a few pins pulse when the supply pulses. Pin 6 and 16 of course. Pin17 pulses half a volt up when power supply surges. Pin11 pulses with surge. 14 rises a bit with each surge.
Looks like pin3 also goes to irs20957s mute. Pin3 has a 1k pulldown on it, then to a 1k to a diode to irs pin2. Pin17 has a 10k straight to a diode to the irs. Cathodes are on irs side. Not really grasping what this is doing.
Also pin 18 comes from a 10k 2.2k divider from +12.
If you don't discharge the rail caps and switch it off, then back on, does it power up normally?
What happens if you power it up from a 12v supply that's about 13v and doesn't sag when the amp is trying to power up.
It's odd that the 5v is pulsing. Do you have your scope grounded to the ground terminal of the amplifier?
What happens if you power it up from a 12v supply that's about 13v and doesn't sag when the amp is trying to power up.
It's odd that the 5v is pulsing. Do you have your scope grounded to the ground terminal of the amplifier?
It will fire up quickly without issue if the rail caps are not discharged.
If i power it up with discharged caps at 14.4v it will boot up in about 8seconds, takes about 30-35 seconds at 10.8v.
Scope ground to edge screw holes which is common - ground.
I just put in irfb4227s in place of 4415. Little has changed.
If i power it up with discharged caps at 14.4v it will boot up in about 8seconds, takes about 30-35 seconds at 10.8v.
Scope ground to edge screw holes which is common - ground.
I just put in irfb4227s in place of 4415. Little has changed.
It appears the outputs high side fets gate is nudging up and coming up gradually as it tries to start. That's interesting..