JL Audio Output Inductor

[jlind54]

Ok, I attached some speakers, turned the bias back down and the voltage on the center leg of the diodes, inductors, and at the outputs is still +40, -27 volts. Do I need to feed the input with a signal and output a decent amount of power to measure or should just attaching the speaker load have been enough?

 

[jlind54]

Disregard the measured values that I posted previously. My LCR meter appears to be badly out of calibration for inductance. I'm going to try to borrow one. If I cannot, I'll drive a high-frequency signal through the inductors and calculate the inductance.

There is no magnet wire that will be damaged by the heat produced by normal operation. Low temp wire is 'solder strippable'. High temp wire has to be stripped mechanically (possibly chemically but I don't know of any chemicals that melt the high-temp insulation).

I was wondering if you ever got a chance to measure the inductance value of a good output inductor on a 500/5?

 

[Perry Babin]

My 'good' LCR meter is giving me unreliable readings. I ordered a new one. It will be here Wednesday or so.

I tried testing with a signal generator but the reference inductor that I was using was giving me high readings. It was either mis-marked or I was making a mistake somewhere.

 

[Perry Babin]

The 500/5 measured at 39.1uH.

 

[jlind54]

Thanks!

 

[jlind54]

Do you know if the operation frequency on the 500/5 is around the 58khz you mentioned for the 500/1?

 

[Perry Babin]

I've never compared the two. If the capacitor connected between pin 6 of the 555 timer and ground is the same value for both amps, I'd expect them to oscillate at the same frequency.

 

[jlind54]

Perry, I was wondering if you could confirm the valve of resistor R813 on the 500/5. In this amp it appears to have been very hot and burned most of the color marking bands off. It faintly looks like 2 orange, a black and a gold band. I believe it might be a 33 Ohm resistor.

 

[Perry Babin]

Correct. Orange, orange, black, gold.

 

[jlind54]

Do you happen to know the value of the large resistors right behind the output capacitors? Mine are a bit defaced from the exploding capacitors so I'm unable to read them. However from your picture and what I can see on mine I'm guessing they are 5 watt resistors.

 

[Perry Babin]

5 ohm 5 watt. The following link is a zipped file of photos of that area.
http://www.bcae1.com/temp/jl500slash5.zip

 

[jlind54]

got them, thanks!

 

[jlind54]

Is there any reason performance wise why the resistors could not be axial mount instead of radial? I'm not finding many options on future or digikey for replacements similar in size to those.

 

[Perry Babin]

I don't have the dimensions. What about this at mouser?
71-CPCC-5-5.0

 

[jlind54]

Didn't look through mousers inventory yet but looking at that part number it looks pretty close. I'll take some measurements when I get home and see how it would fit. Thanks

 

[jlind54]

Ok, its been a while but I've finally collected all the parts I think I need to get the amp back up and running. I've swapped everything out and powered it up. 4 channels all seem to work just as expected, sub channel also appears to be alive. I'm going to run it on the bench for a while to monitor its condition. Do you have any ideas of what would cause the output capacitors and inductors to melt down but leave the outputs and power supply section in working condition?

 

[Perry Babin]

It could be that a winding shorted on the inductor first. That would have caused overheating and could have produced too much of a load for the capacitors (from the high frequency carrier passing through the inductor). Of course, this is a guess.