JL Audio 500/1

[mike49504]

Does anyone know the value of the gate resistors on this amp..

The board says rev 11

And its using IRFZ44's as the power supply fets

 

[bdgf2004]

http://www.diyaudio.com/forums/car-audio/153491-jl-audio-500-1-repair-info.html

 

[Perry Babin]

47 ohm. When you install them, install them with about 3/16 of clearance so they don't damage the board if it fails again.

 

[mike49504]

I noticed the outputs are shorted also..

When ordering replacements do i order the IRF540's or the 540A's ??

Just asking because i think i read somewhere that theese amps do funny things sometimes when replacing the outputs..

 

[Perry Babin]

I've used both the IRF540 (no suffix other than PBF) and the IRF540A with no problems. The IRF540N was the transistor that caused problems in some amp but those were class AB amps. I don't know if they cause any problems in this amp.

 

[mike49504]

Ok almost done putting the parts back into this amp..


Which one is the Bias pot in this amp or are both of them bias pots??

R565 and R563

 

[Perry Babin]

Neither is bias. In general, class D amps don't have bias pots. Don't turn either one.

 

[mike49504]

Do you happen to know the values of R515 and R516 ??

 

[Perry Babin]

R515 = 10 ohms
R516 = 47 ohms

 

[mike49504]

Thanks..

The drivers 4 the othputs are 2N3906's Locations

Q510
Q509
Q503
Q501

Correct or are there more drivers for the outputs??

 

[Perry Babin]

Q508 and Q502 are also drivers.

 

[mike49504]

Ok amp powers up and idles perfectly..

2 of the outputs have 82 volts of rail on them..

Other 2 outputs have no voltage on them..


Any ideas?

 

[Perry Babin]

You need to be more specific. Each of the 4 transistors has 3 legs.

What is the DC voltage on the speaker terminals (one positive and one negative terminal) with the black probe on the amp ground?

 

[mike49504]

With Black meter probe on ground ..


Positive speaker terminal:0.14 volts

Negative speaker terminal:0 volts


On the outputs

Q504 and Q507 show 82 volts of rail on the center legs..

On Q505 and Q506 I get 0.04 volts on all 3 legs of each output


Amp has no output

 

[Perry Babin]

If you short pins 1 and 2 of the op-amp indicated in the photo, do you get any square wave oscillation on the outputs?

Be careful, if it's shutting down for some reason, this could cause it to draw excessive current.

 

[mike49504]

im gonna test that in a few..

My question is on the regulator U601 (7805) are legs 2 and 3 connected together ??


Because from leg 2 to leg 3 i get 26 ohms is that normal for this amp?

 

[Perry Babin]

I've never had any reason to measure the resistance between those two legs but it seems too low. Pull the regulator and check the board and regulator to see where the low resistance is.

 

[mike49504]

im getting the 26 ohms on the pads themselfs from 2-3

 

[Perry Babin]

Do you still read low resistance if you unplug the preamp board?

 

[mike49504]

yes