Hello,
The left channel outputs a strange sound at high volume (only when a subwoofer is connected to it, see the oscilloscope photos), like popping noises. The right side doesn't have this problem.
I tested the small transistors with a multimeter, and they seem to be functional. I replaced all 8 MOSFETs on the left side with new ones (4 were burnt out).
Thank you for helping me solve this problem.
The left channel outputs a strange sound at high volume (only when a subwoofer is connected to it, see the oscilloscope photos), like popping noises. The right side doesn't have this problem.
I tested the small transistors with a multimeter, and they seem to be functional. I replaced all 8 MOSFETs on the left side with new ones (4 were burnt out).
Thank you for helping me solve this problem.
What did you use as replacement FETs?
What were the originals?
Were the replacements from a reputable distributor?
Is the distorted side the repaired side?
What were the originals?
Were the replacements from a reputable distributor?
Is the distorted side the repaired side?
Hello,
What did you use as replacement FETs?
IRF540N (Infineon brand)
What were the originals?
IRF540 (STMicroelectronics brand)
Were the replacements from a reputable distributor?
Arrow, it's good distributor ?
Is the distorted side the repaired side?
Yes
What did you use as replacement FETs?
IRF540N (Infineon brand)
What were the originals?
IRF540 (STMicroelectronics brand)
Were the replacements from a reputable distributor?
Arrow, it's good distributor ?
Is the distorted side the repaired side?
Yes
The N-version sometimes causes problems.
In general, the originals are the best option but I used the IRF3415 with good results.
Arrow is OK.
Did you reset the bias when you replaced the FETs?
In general, the originals are the best option but I used the IRF3415 with good results.
Arrow is OK.
Did you reset the bias when you replaced the FETs?
Okey,
But original mosfet not avaible with Arrow distributor, I will also order some IRF3415 later.
Did you reset the bias when you replaced the FETs?
No, I didn't know I had to do a reset, how to proceed ?
Thank you for your help
But original mosfet not avaible with Arrow distributor, I will also order some IRF3415 later.
Did you reset the bias when you replaced the FETs?
No, I didn't know I had to do a reset, how to proceed ?
Thank you for your help
https://octopart.com/search?autosugg_idx=0&q=irf540pbf¤cy=USD&specs=0
When you replace the outputs, you always have to reset the bias.
For this, it's a bit different from other amps.
Turn the bias pot fully counter-clockwise and while watching the current draw from the 12v supply, turn the pot clockwise until you just see a small increase in draw. Load the amp with a dummy load and drive a signal into the amp (100Hz is OK) and look at the output of the amp while increasing the signal. If the amp doesn't clip symmetrically, top and bottom (below is under-biased), increase the bias until it does.
When you replace the outputs, you always have to reset the bias.
For this, it's a bit different from other amps.
Turn the bias pot fully counter-clockwise and while watching the current draw from the 12v supply, turn the pot clockwise until you just see a small increase in draw. Load the amp with a dummy load and drive a signal into the amp (100Hz is OK) and look at the output of the amp while increasing the signal. If the amp doesn't clip symmetrically, top and bottom (below is under-biased), increase the bias until it does.
Attachments
Okey, I will follow these instructions when I have some free time. Thank you for your help. Have a great day 😉
Understand that all components need to be tightly clamped down to the heatsink when adjusting the bias current.