i'm trying to fix my jl 500/1.........i've replaced all the irfz44n's with exact replacement.........also replaced the irf540's with irf540n as the non n's are hard to find........i replaced the 44's resistors with 47 ohmers..........irlz34n was also replaced.
no lights, power or anything..........before i replaced the parts i had a green light...........so i replaced the blown parts which was the 44's and resistors and after further checking i found a couple of the 540's bad and replaced those as well.........the 44's were exact replacement and the 540's were replaced with the "n " version by IR..........i checked all the solder joints and they appear to be good.....
it seems that the irf540 is obsolete.......or at least the ones by "ir".
i wonder if the fairchild IRF540A would be a better replacement?
Once I found JL500/1 amp not working because the through-hole plating malfunctioned (upper and lower tracks not connected). There are hundreds (and tiny) through holes in this amp.
Better to work with service manual or at least a schematic to fix this kind of amp.
I dont think the 540N will cause trouble , at least the power or protect light would be turned on.
Do you have a scope ? If so try to check the gate´s signals of the irfz44. If you dont have a scope use a multimeter in frequency mode and check the output signals of the SMPS - chip. Usually a µPC494 (TL494) or similar SMPS-chip . If you find output signals around 20 KHz or higher the chip is working and tries to power the IRFZ44 . Follow the output signals from the TL494 , usually you ´ll find some small signal transistors (usually 2SA1266, or 2SA1015) connected to the outputs. The small signal transistors drive the IRFZ44 gates .
If there ´s no output on the SMPS-chip it is probably disabled, but then the protect-LED should be lit. Please check the fuse again and make sure 12V, GND and remote signals are ok.
yeah, the preamp board is plugged in............fuse? i don't see any kind of a fuse in this amp.......ok i found 2 through-hole plating malfunctions......one in the topside of the 44n's and one on the bottom of the 540n's............and the auto turn on is connected........i'm still checking....
problem solved.........replacing all the TO-220 FET's did fix the amp........the remote wire came loose.......giving me a headache.....thanks to everybody who took the time to read and post to my thread.......perry, thank you for taking the time to post a picture and for me to check the voltages on the 10 pin plug.. that's when the amp came back to life on the bench, and then later i found the remote wire came loose......it's all good.
i found that a no.9 or so open ended ignition wrench from craftsman is perfect for removing these clamps in most cases. the wrench is thin enough and has a perfect angle on the open rounded end to pop those clips right out with downward leverage against the heatsink. to pop them back in i just line them up in place and tap them in with the plastic end of a larger screwdriver. trial and error led me to this idea as well as a few bent up clips in the procces.