JBL SUB135S bad startup, not triggering out of standby

[Uranium-235]

I was given this a few years ago by my sisters then fiance

when I first got to my apt I used it for a few months but it ended up being kind too powerful for such a closed space, even though I could turn the sub down in the theater (sub does not have a volume control), even at low levels the bass was simply at such a low frequency it was pretty loud even at low volumes. It was a yamaha amp that has an amp built in for its own external sub, and I put that for the sake of my neighbors

I didn't use it for like a year, then I moved into my parents and I hook it up, the normal startup routine (instead of a steady back and forth for a few seconds) is drastically bad. And when I hook the LFE from the amp to it, it dosen't trigger out of standby, and occassionally does the same hard startup pump but once once or twice a minute randomly

here is a video of its startup routine, pics of the circuts (which look ok, but lots of seeminly melted gook everywhere. I'm not sure whats going on here. no bloated caps, so could be some of the regs? I've never dealt with sub amps before..or any kinda audio amps really

[Koda]

Re: JBL SUB135S bad startup, not triggering out of standby

I see some heavy discoloration under the transistors on pic3, maybe there is the problem, I would check those visually to see if something is burned. Had an amp with three TDA 2030a that was working on 2 channels instead of 3. Found discoloration under 1 of them and at a closer look I found a hairline crack on it. After replacement the amp worked great.

[Uranium-235]

Re: JBL SUB135S bad startup, not triggering out of standby

Actually, Q106 got so hot, the solder under it melted and it disconnected from the board :O

you can't find this board anymore, so i'm seeing about replacing these, i'm assuming cause they got and have 3 legs, are mosfets

they say

F 42
D882-Y

F is probaly fairchild, which means its probably one of these

http://search.digikey.com/us/en/cat/...1376376?k=D882

not sure if I want to get another one of these. does anyone know of something that can work and might be cooler?

I should probably replace the caps around these, i'm guessing

[budm]

Re: JBL SUB135S bad startup, not triggering out of standby

I have seen many import with bad brown glue, they are conductive and also corrosive. You need to remove them and see if it had eaten away any copper traces and wires. I have seen so many consumer electronics got damage by this kind of glue, these day they changed to white pliable glue now. Since that small board is the audio input amp, if it does not put out any audio for the detector circuits to turn the power amp on, you will not get the sound.
Do fix the over heated solder joints also.

[Agent24]

Re: JBL SUB135S bad startup, not triggering out of standby

Actually, Q106 got so hot, the solder under it melted and it disconnected from the board :O

you can't find this board anymore, so i'm seeing about replacing these, i'm assuming cause they got and have 3 legs, are mosfets

they say

F 42
D882-Y

F is probaly fairchild, which means its probably one of these

http://search.digikey.com/us/en/cat/...1376376?k=D882

not sure if I want to get another one of these. does anyone know of something that can work and might be cooler?

I should probably replace the caps around these, i'm guessing

The model number seems to make sense, but it's not a MOSFET, rather a bipolar NPN transistor. http://www.fairchildsemi.com/pf/KS/KSD882.html

I wouldn't necessarily blame the transistor for desoldering itself. Could have been caused by a fault elsewhere (like that glue!) or someone running it at volume too high.

Not sure what is supposed to happen but in the video it looks like the thing is trying to kill the speaker, though...

[Koda]

Re: JBL SUB135S bad startup, not triggering out of standby

The discoloration on the 3rd pic is not caused by glue, it's due to excessive heat from the components and some of those components could be dead due to the heat

[Uranium-235]

Re: JBL SUB135S bad startup, not triggering out of standby

The discoloration on the 3rd pic is not caused by glue, it's due to excessive heat from the components and some of those components could be dead due to the heat

actually, what I didnt' realize until I got the subwoofer itself disconnected from the amp is under that black spot, is that fucking glue! its all hard and some joints seem corroded

I think these trannys are to blame. they are the ONLY component that got so hot it literally unsoldered itself, and no component near them got unsoldered. Unfortunately, I think it burnt the pads, and on one of them I didnt' realize they were broke and I think I tore one of the connecting traces from the pad to the board in half. I could get some small insulated wire and try to connect these trannys to the adjacent joint with that

I wouldn't necessarily blame the transistor for desoldering itself. Could have been caused by a fault elsewhere (like that glue!) or someone running it at volume too high.

Not sure what is supposed to happen but in the video it looks like the thing is trying to kill the speaker, though...

this speaker has no volume control, it runs 100% at all time (unless its idle), with the only volume control on the theatre amp it hooks to.