Bought this amp untested and of course it arrived DOA. Power supply fets (IRFZ44) had failed and although I’m not reading any shorts on the output mosfets I can tell one has definitely been replaced so it has had a failure at some point. I am trying to determine if the power supply drive circuit is intact. If I apply just remote and ground the power supply gate drive signal looks close to what I would expect
iCloud
Based off of that I dropped in a new set of IRFZ44’s and it powered up without drawing excessive current and idled with no issues. Rail voltage looked good and there was no excessive DC on the outputs. However the gate drive signal looks a lot different now unless I drop the input voltage to about 12.2 volts and then it looks like what it did before the new fets were installed. Here is what it looks like with about 14.2 volts of input.
iCloud
It’s been a while since I worked on an amp. Maybe this isn’t a big deal. I only remember seeing this one other time but the PWM chip in that amp was an SG3525. Just wanted to run it by the pros before moving forward with trying to find new outputs for the channel that has been worked on previously. I’d like a matching set of outputs in it.
iCloud
Based off of that I dropped in a new set of IRFZ44’s and it powered up without drawing excessive current and idled with no issues. Rail voltage looked good and there was no excessive DC on the outputs. However the gate drive signal looks a lot different now unless I drop the input voltage to about 12.2 volts and then it looks like what it did before the new fets were installed. Here is what it looks like with about 14.2 volts of input.
iCloud
It’s been a while since I worked on an amp. Maybe this isn’t a big deal. I only remember seeing this one other time but the PWM chip in that amp was an SG3525. Just wanted to run it by the pros before moving forward with trying to find new outputs for the channel that has been worked on previously. I’d like a matching set of outputs in it.
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The supply is regulated and the duty cycle is being rolled back as the rail voltage reaches its target voltage.
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Perry in your opinion is the drive circuit ok?
Also while I have your attention, what is a good substitute for the BUZ11’s in the output section?
Also while I have your attention, what is a good substitute for the BUZ11’s in the output section?
The power supply appears to be working normally, at this point.
The diagram (see attached) calls for IRF540s and IRF9540s. Don't order the IRF540N. The N-version causes problems in some amps.
The diagram (see attached) calls for IRF540s and IRF9540s. Don't order the IRF540N. The N-version causes problems in some amps.
Hmm my amp must be a different version than the schematic you provided. Mine only has a single pair of BUZ11’s in each channel.