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ivkata 14th March 2013 01:47 PM

jl audio 500/1 power supply wont turn on
i purchased this amp and another or ebay as broken for parts /repair and for my surprise the other unit worked just fine .This Jl 500/1 dosent look like it was ever repaired in the past ,nor anything looks burn here is my test results :

-when i connect it to my psu the green light comes on ,amp draws 3a current right away ,no power suppy start pulse to be seen .Eventually the power light does away in about 1 min ,current thru the amp is still 3 amp.If i swich the singnal sensing button to on the power light comes back on ,draws a little more current .

There is no dc on the speaker terminals ,no audio output neither .moving switches or pots dosent efect the unit

board: rev 10

Osvaldo de Banfield 14th March 2013 02:52 PM

I don'y know about this amp specifically, but may happen that this set need a separate enable input?

evianamp2011 14th March 2013 05:44 PM

Have you looked closely at the legs of all the transistors that are mounted to the heat sink? The rectifiers legs usually break...but check all of them very closely, heck use a 5x magnifier.

Perry Babin 15th March 2013 12:09 AM

1 Attachment(s)
Post the DC voltage on the 10 pin connector after the power LED goes out. Use the pin numbering shown on the attached photo.

Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:

ivkata 15th March 2013 02:43 AM

Pin 1: 4.6
Pin 2: -14.3
Pin 3: 12.9
Pin 4: 5.3
Pin 5: 12.3
Pin 6: 12.4
Pin 7: 0.7
Pin 8: 12.2
Pin 9: 12.2
Pin 10: 0 .0

Perry Babin 15th March 2013 03:03 AM

Except for pin 1, which is a bit low, those look OK.

Do any of the gate resistors for the power supply look burned? They Are R600-R607.

kds9591 15th March 2013 04:48 AM

Normal idle current for this amp is 1.5A-1.7A but will draw as much as 3.5A before it settles down to 1.5-1.7A.

If you have the rear heatsink off check output MOSFETS Q504-Q507 IRF540's to see if any of them get warm or hot with no signal and no load. If any do check to see if shorted or leaky. If ok check Q500-Q503 and Q508-Q511. Now if you do have a problem with the output MOSFETS or the output circuit your power supply MOSFETS will get warm or hot but that does not always mean they are shorted or leaky as well.

Do you have a O'scope?

ivkata 15th March 2013 05:08 AM

it appears that all the psu transistors failed even tho there was no residue or burned resistors to be seen .I dont have irfz44n now i do have irf3205 can i use them without replacing the gate resistors as they all appear in tolerance

kds9591 15th March 2013 05:27 AM

I'd stay with the original IRFZ44's. Also check your output MOSFET's and Q500-Q503 and Q508-Q511 because if shorted or leaky they will be the root cause of the power supply MOSFET's failing in most cases.

Perry Babin 16th March 2013 01:01 AM

The original Z44s are good enough. I've been using IRF3205s in the most of the JL 500s that I've seen lately (I've done about 10-12 so far) and they appear to be OK. I haven't done enough or checked enough after long-term use to say that the drivers will hold up. Their current rating is high enough but they may run hot.

Are you sure that the FETs failed with absolutely no visible damage to any of the power supply gate resistors?

After removing the FETs and cleaning up the solder pads (to ensure that there are no solder bridges), check every gate resistor to confirm that all are within tolerance.

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