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Rzabo2004 25th November 2012 04:24 AM

Jl audio 500/1 help
Hey guys I just got a jl audio 500/1 and it powers on and plays very low distorted sound and has 80volts at the speaker terminals anyone have any ideas on what could be wrong with it

S Merlington 25th November 2012 05:41 AM

Sounds like you have blown output transistors

Rzabo2004 25th November 2012 06:03 AM

Just got done replacing all four output transistors and still have the same problem. Also the amp is making a high pitched noise I can't tell where it is coming from the noise is not very loud but it is noticeable.

S Merlington 25th November 2012 06:41 AM

Check your power supply fets to see if any are shorted and re-check your outputs to see if any are shorted ..

Dont apply power anymore to the amp until you check both the power supply fets and outputs If you get any low reading post your results

Perry Babin 25th November 2012 01:30 PM

Check the outputs that you removed. Were any shorted?

Do you have a scope?

Rzabo2004 25th November 2012 01:38 PM

I do not have a scope. Is there one that you recommend getting because I will buy one. One transistor was shorted out I could see physical damage to the transistor. I replaced all if them. 25th November 2012 01:52 PM

Did you check the gate resistors?

Perry Babin 25th November 2012 01:52 PM

Check the resistors and transistors that were driving the shorted transistor to see if any are defective/out of tolerance.

What's your budget for a scope?

Do you want a new one or is a used one OK?

Rzabo2004 25th November 2012 02:03 PM

I never looked into what scopes are going for but I'm willing to invest in one. Used would be fine. Can I check transistors in the circuit or do I have to remove them

Perry Babin 25th November 2012 03:41 PM

If you're going to buy a used one, find one with a guarantee or one with a locked waveform displayed. If you're unsure, post a link to the one you're interested in here (or email it to me if you're concerned that someone may bid against you on it).

The BK Precision 2120B was a good option for a new scope and still is if you can find one for about $400.

For used scopes, I recommend the 400 series (465B preferred) or the 2200 series Tektronix scopes. Avoid the 2400 series unless you can afford to lose whatever you paid for it.

For audio work, I'd avoid the purely digital scopes.

You can check the driver transistors in the circuit but unless they're shorted, it may be difficult to tell if they're otherwise defective (leaky or open).

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