I've recently acquired a JL 500/1v2 that has apparently been abused. I opened it up and Q600-Q607 were definitely toast along with the gate resistors R600-R607. With those items removed I figured I would give it some juice and take some measurements on the board... however I noticed upon connecting the ground and 12volt source the amp flashes the protect light then the power light stays illuminated for approximately 40 seconds without ever connecting the remote to 12volts. I was wondering if thats normal or if this amp is hopeless to repair.
haha, that should have been the first thing I should have checked... forgot it had that feature now that the case is all taken off. I'll check it out and report back in a bit.
well, that was what was causing it to power up and turn back off. are the outputs considered leaky/bad if any of the legs measure in the the 12k ohm range... most measure in the 36-45m ohm range... trying to figure out what made the power supply in this thing melt down...
Generally, defective output FETs will read very near 0 ohms between at least two of the 3 legs of any individual transistor. They may be OK.
If the outputs are not shorted I'm guessing something with the power supply drive is out of whack for it to roast all the fets and gate resistors. Are there any down and dirty methods of getting a ballpark of it's operating condition having only a multimeter?
Sometimes, the power supplies in these amps (and others) fail for no apparent reason. Replacing the power supply FETs and gate resistors will often be all they need.
I've been using the IRF3205 in place of the IRFZ44. I'd suggest that you use them.
I've also been using the IRF3710Z (Z is very important) in place of the IRF540s in the output stage. I've never had any amps using that combination fail (failure of the PS or output FETs).
A multimeter may be enough. After removing the power supply FETs and burned gate resistors, removing all of the old solder and cleaning the board (acetone and toothbrush), I'll tell you what to check.
I've been using the IRF3205 in place of the IRFZ44. I'd suggest that you use them.
I've also been using the IRF3710Z (Z is very important) in place of the IRF540s in the output stage. I've never had any amps using that combination fail (failure of the PS or output FETs).
A multimeter may be enough. After removing the power supply FETs and burned gate resistors, removing all of the old solder and cleaning the board (acetone and toothbrush), I'll tell you what to check.
I'm addicted to tinkering so I stayed up a bit late last night cleaning it up. I've got the fets and gate resistors out. With how burned the resistors were I half expected they would read high... They measured between 8-12 ohms with the exception of one that was near 39
If you removed all of the solder and flux and are 100% sure that there are no solder bridges, measure the DC voltage on leg 3 of driver transistors Q609 and 610. You'll have to power the amp up and wait about 10 seconds before measuring the voltage.
This might be a dumb question but which leg is three? Is it the leg that went to the gate resistor?
On the IRF3205 is there an specific suffix you use? I'm at work and doing some parts searching. Found the following:
Invalid Request
Looks like they have a higher watt rating than the originals.
Invalid Request
Looks like they have a higher watt rating than the originals.
When measuring this voltage do I need to use a meter that reads true rms or will a cheap craftsman meter work?
You don't necessarily need a true RMS meter but you need a meter that has enough bandwidth to allow you to read something. Post what you get with the meter you have.
Ok, measured the voltage at those pins and also at the pads where the new gate resistors will go and got 4.74 volts. Also, while I was plugged in I measured the op amps and they have +/- 14.9
All it may need is new FETs and resistors.
Before applying power to the amp, insert a 10 amp fuse in the B+ line and have all transistors tightly clamped to the heatsink. Also make sure that all heatsink mounted components have insulators between them and the heatsink. You'll need to remove the old heatsink compound and replace it with new compound.
Before applying power to the amp, insert a 10 amp fuse in the B+ line and have all transistors tightly clamped to the heatsink. Also make sure that all heatsink mounted components have insulators between them and the heatsink. You'll need to remove the old heatsink compound and replace it with new compound.
I was wondering if these part numbers you give below are ok to use in the older version 1 JL 500/1 amps:
IRF3205 in place of the IRFZ44.
IRF3710Z in place of the IRF540
IRF3205 in place of the IRFZ44.
IRF3710Z in place of the IRF540
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