Hi guys,
One of my car amplifiers, a JBL CS60.2 seems to have died of loneliness. No audio, the 3 blue LED are flashing like disco.
I thought the FETs are dead and it's gonna be a simple job, but neh... FET IRFZ48 were just fine. I've replaced them anyway, along with the PWM controller, TL494. The final transistors, TIP35/36 checked too - tip-top! F12C20 rectifiers are fine too.
Just can't figure out. Some of the voltages for PWM are messed up, the trafo makes a buzz, the FETs gets warm (mounted on the heatsink, otherwise will fry in a few sec) and the main 14v voltage goes down to 10.2v as soon as the FETs are soldered on board. Also the power supply heatsink gets warmy and that's weird, as the amplifier it has protection triggered and it's idling at its best.
Any idea? Thank you guys.
One of my car amplifiers, a JBL CS60.2 seems to have died of loneliness. No audio, the 3 blue LED are flashing like disco.
I thought the FETs are dead and it's gonna be a simple job, but neh... FET IRFZ48 were just fine. I've replaced them anyway, along with the PWM controller, TL494. The final transistors, TIP35/36 checked too - tip-top! F12C20 rectifiers are fine too.
Just can't figure out. Some of the voltages for PWM are messed up, the trafo makes a buzz, the FETs gets warm (mounted on the heatsink, otherwise will fry in a few sec) and the main 14v voltage goes down to 10.2v as soon as the FETs are soldered on board. Also the power supply heatsink gets warmy and that's weird, as the amplifier it has protection triggered and it's idling at its best.
Any idea? Thank you guys.
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Does it still draw excessive current if you remove the rectifiers (and clean the solder pads so there are no solder bridges)?
Can you power it up long enough to see if the current draw changes if you twist/push/pull on the power transformer?
What was strange about the voltage readings on the 494?
What was strange about the voltage readings on the 494?
Hi Perry, sorry for the late response, I was out of Internet for a few days.
Nope, doesn't matter if I twist/push on the transformer, still buzzing and drawing current. As long as the FETs are onboard, it's drawing current for some reason. I've even removed and checked the transformer, looks fine, no shorts.
First 4-5 sec after I connect the power, I got the normal nominal voltage, 14v and no buzzing, then, bang!, it goes down to 10v and it starts drawing current, but I guess that's the power transformer doing its job.
Nope, doesn't matter if I twist/push on the transformer, still buzzing and drawing current. As long as the FETs are onboard, it's drawing current for some reason. I've even removed and checked the transformer, looks fine, no shorts.
First 4-5 sec after I connect the power, I got the normal nominal voltage, 14v and no buzzing, then, bang!, it goes down to 10v and it starts drawing current, but I guess that's the power transformer doing its job.
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With no rectifiers, the amp should draw virtually no current. It should only draw more than a fraction of an amp when there is a load on the secondary.
Try pulling the secondary windings (outer two windings only unless it's easier to pull all of the secondaries). Does that change the amount of current the amp draws?
Do you have a scope?
Do you have a multimeter that can measure frequency?
Try pulling the secondary windings (outer two windings only unless it's easier to pull all of the secondaries). Does that change the amount of current the amp draws?
Do you have a scope?
Do you have a multimeter that can measure frequency?
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