Hello.
I bought stetsom ex8000eq(1ohm) with a blown ps section. It had water damage, ps fets had pretty heavy oxydation between all 3 legs and probably gate turned fully on and blew the fets(most drain/source legs were melted).
I put new irf1404 in because i had enough of them laying around and the amp came back to life but still has some problems. I didnt notice main problem on the first day because with small bench supply it seemed normal that amp wont turn on with first remote signal.
With further testing i understood that when applying remote with rail caps dropped to 0V(actually anything below 7V in rails) then the amp goes into protect and flashes red once(means overload or short in the output) but applying remote second time will always turn the amp on. So anything above 7V and amp will turn on right away.
Second problem is when unplugging remote theres a weird noise/sound in the output and speaker is slightly sucked in. On the scope you could see something close to sinewave at the output right after the remote is removed and its present on both "channels".
Both problems are still present either having speaker connected or not.
I have desoldered all the the IC's and drivers incase there is oxydation underneith or something and everything looks perfect. All the voltage regulators test fine. All the drive signals on both sides of the amp are identical and same goes with ps section. I didnt change ps drivers because i saw no need for that at the time.
Leaving these problems aside amp works well, it has played a few hours on workbench and i put in car for about 15 minutes to get some heavier stress on it and it works just fine. One thing that looks weird to me is that output inductors get hotter that i'm used to. After 10mins or so they are quite untouchable for hand(both inductors a equally warm/hot and output caps all read fine.
If anyone has some advice or what to check next your input is appreciated.
Thanks in advance.
I bought stetsom ex8000eq(1ohm) with a blown ps section. It had water damage, ps fets had pretty heavy oxydation between all 3 legs and probably gate turned fully on and blew the fets(most drain/source legs were melted).
I put new irf1404 in because i had enough of them laying around and the amp came back to life but still has some problems. I didnt notice main problem on the first day because with small bench supply it seemed normal that amp wont turn on with first remote signal.
With further testing i understood that when applying remote with rail caps dropped to 0V(actually anything below 7V in rails) then the amp goes into protect and flashes red once(means overload or short in the output) but applying remote second time will always turn the amp on. So anything above 7V and amp will turn on right away.
Second problem is when unplugging remote theres a weird noise/sound in the output and speaker is slightly sucked in. On the scope you could see something close to sinewave at the output right after the remote is removed and its present on both "channels".
Both problems are still present either having speaker connected or not.
I have desoldered all the the IC's and drivers incase there is oxydation underneith or something and everything looks perfect. All the voltage regulators test fine. All the drive signals on both sides of the amp are identical and same goes with ps section. I didnt change ps drivers because i saw no need for that at the time.
Leaving these problems aside amp works well, it has played a few hours on workbench and i put in car for about 15 minutes to get some heavier stress on it and it works just fine. One thing that looks weird to me is that output inductors get hotter that i'm used to. After 10mins or so they are quite untouchable for hand(both inductors a equally warm/hot and output caps all read fine.
If anyone has some advice or what to check next your input is appreciated.
Thanks in advance.
I did some quick testing in the morning. Found out that when D44(circled red) is removed then amp turns on even with 0V in the rails. When D44 is soldered in and removing 2 (D10&11) diodes on the same trace(next to both N9260 pnp's) amp still protects.
So i pretty sure i can leave D10&D11 out of this.
The via that goes through the board at D44 connects to via circled in blue at the PIC ic. Trace is grounded with 4.7k resistor which is parallel with ceramic cap and a diode. Other end of the trace goes to PIC ic pin nr 4. I will look into this in the evening.
So i pretty sure i can leave D10&D11 out of this.
The via that goes through the board at D44 connects to via circled in blue at the PIC ic. Trace is grounded with 4.7k resistor which is parallel with ceramic cap and a diode. Other end of the trace goes to PIC ic pin nr 4. I will look into this in the evening.
Attachments
Hmm strange. I desoldered all the components next to the rail caps one by one to measure them outside the circuit. I guess they and two N9260 at the top and bottom of the picture are responsible for the overload circuit? Anyway i checked them all and found nothing wrong nor out of tolerance.
I guess it had to be cold solder or maybe water+dust residue or something because now the amp fires up every time no matter the voltage in the rails.
If nothing changes i think i can count that problem solved.
But there is still that weird noise that happens for millisecond when remote removed.
I tried to capture it with phone. When amp is turned on there is 0v dc offset. Both terminals sit at the same voltage(~57v atm) but right after turning off it turns into --> see the pictures.
Right after removing remote theres no more than 0.1v dc offset between two terminals. Both sides generate somewhat the same signal.
I guess it had to be cold solder or maybe water+dust residue or something because now the amp fires up every time no matter the voltage in the rails.
If nothing changes i think i can count that problem solved.
But there is still that weird noise that happens for millisecond when remote removed.
I tried to capture it with phone. When amp is turned on there is 0v dc offset. Both terminals sit at the same voltage(~57v atm) but right after turning off it turns into --> see the pictures.
Right after removing remote theres no more than 0.1v dc offset between two terminals. Both sides generate somewhat the same signal.
