Loudspeakers - Speakers emitting high frequency....

[museav]

I think the relevant point is that the speakers were modified in a manner such that they are not being used as intended. I would think JBL would have to refuse any warranty service simply as accepting it could be seen as implicit acceptance of the modifications. In addition, as far as I can tell from what has been posted, it would be difficult to say definitively that the problems being experienced might not be related to the modifications made.

While you may have accommodated this in your modifications, for others that may not be aware and could take what was said wrong, there is often much more to making a speaker flyable than simply adding fly points.

[Thefoxygranpa]

Originally Posted by museav

I think the relevant point is that the speakers were modified in a manner such that they are not being used as intended. I would think JBL would have to refuse any warranty service simply as accepting it could be seen as implicit acceptance of the modifications. In addition, as far as I can tell from what has been posted, it would be difficult to say definitively that the problems being experienced might not be related to the modifications made.

While you may have accommodated this in your modifications, for others that may not be aware and could take what was said wrong, there is often much more to making a speaker flyable than simply adding fly points.

Ah yes, the reason I brought my modifications into this topic was to ask opinion on whether they would service this although I did make alterations.

I just re-read my Warranty paper and it does look that JBL would not cover this under warranty because of what I did. I haven't received an invoice from the repair company yet, so I assume I'll know soon enough if I'll be forking out the cash for the repair.

Thanks!

[Thefoxygranpa]

Yarg!

So my speaker comes back yesterday, I take a look at the invoice and it says "Can not get it to reproduce sound you described. Check your XLR cables and AC power if the problem persists"

Now this had to go to philly to get repaired, and it turns out they did nothing!

My question now is where do I go from here? I got the speaker back, put it in my office and powered it on. I had the gain all the way down, and after 30 minutes[amps warm to touch], it started to produce this frequency again!

What would someone suggest! I'm at a loss as to what I should do, and even tempted to send this speaker straight to JBL if they do repairs.

Thanks CB!

[waynehoskins]

The first thing that comes to mind is perhaps a switching power supply going unstable or losing regulation with heat and time. It may require going back to the guys who made it, or some time in the service manual at least performing tests. Just my guess, though, and I could be totally wrong.

[RichMoore]

Are you powering the speakers from regular wall outlets? If so, that could be your problem.

You might want to investigate "power conditioners", which 'clean' the ac power.

Most likely, the shop where you sent the speaker to be checked out was using 'clean' power at the work bench and noticed no problem, which could be an indicator that your power is 'dirty'.

[Thefoxygranpa]

I should mention that both the speakers are running off of the same power line, however one makes the noise and the other does not.

[SHARYNF]

this may sound crazy but take the speaker to another location say your home and try it there, it is possible that you have something in that speaker/amp that is sensitive to a high frequency signal that it is picking up, could be another electronic item near where you have been testing it
Just a thought
Sharyn

[FMEng]

The problem is clearly internal to the speaker. Someone did a poor job of evaluating it. That has to be frustrating. Basically they just plugged it in, ran it for a few minutes, and gave up when they did not hear the problem. Had they let it run for awhile, they would have caught the problem.

Your problem is typical of a thermal intermittent, which is a fairly common way for electronics to act up, particularly in things that run rather warm, like amps. When it warms up, some section starts oscillating. It could either be in a power supply regulator or an audio stage.

Send it in again with a more detailed description of the problem. The important points are that the noise occurs with no audio cable connected, with the volume turned down, and AFTER it has been powered up for some time. Given that info, any good technician should be able to reproduce the problem, then fix it. Make sure to tape a type written note directly to the speaker, to make sure the bench tech sees it.

I would also instruct them not to return the speaker un-repaired without calling you first. If they can't fix it again, and call you, then I would tell them to replace all of the electrolytic capacitors in the power supply, especially those located next to hot things. If the quantity is reasonable, do them all. Electrolytics are a very common failure item in hot blooded equipment, and they are not usually expensive parts or time consuming to do. Just replacing a bunch of parts like that is a gamble, but one based on an educated guess. I would take that gamble since shipping a heavy speaker around is expensive.

[jkowtko]

When my Mackie SRM450 had a problem, Mackie allowed me to remove the amp from the back of the speaker cabinet, and replace just the amp. They shipped me a new amp, I swapped them out and returned the broken one. You might want to check with JBL to see if they will do this -- a much easier way to get the speaker repaired, and you won't have to worry about cabinet modification issues.

[waynehoskins]

By the way, since it's on your desk, you might open the back up and see if there are any of the standard signs of catastrophic failure on the power supply or PA sections.