PB12 problem

[Donald]

I have had the motorboating problem mention in the service bulletin supplied by someone here.

What is the brown stuff at the base of the caps and around the transformer? It appears to have oozed from somewhere. In the photo called resist, check the flying resistor with the silicon blob above R42. Bad/burnt joint. And check the solder joints on the amp. Looks like it was done by hand, not automation. Very dirty.

Could the brown junk have come from the caps? Check other messages for pics.

[Donald]

amp

[Donald]

caps

[Donald]

resistor

[Donald]

transformer

[Don C]

The stuff around the solder joints on the board is just flux. Since I don't see so much flux elsewhere, I'd think that the board has already had that connection reworked once. It is considered good workmanship to clean off the flux with alcohol when finished soldering, but it is not uncommon to see it. I doubt if it is causing a problem, but I'd clean it off anyway.
The other brown stuff looks like glue. Is the stuff solid, are the caps glued in place by it?

[Donald]

The stuff could be glue. It is brittle. It is around the base of both caps. It looks like they stood the whole unit up before the glue set. It appears to have run down on the windings and base of the transformer. In the caps photo you can see it on top of some vertically mounted components labeled R10C.

I plan to resolder the amp and I will clean off the flux.

Not that it makes much difference but the black speaker wire was on the + post and the red on the -

[boputnam]

Great reply, Don c... :thmbsup:

Now, about this...:
Originally posted by Donald
Not that it makes much difference but the black speaker wire was on the + post and the red on the - If you mean for the LF, that wouldn't necessarily be wrong.

Lemme search for that schematic for the L222 network... :scoot:

*****

I don't have it... Anybody?

[4313B]

L222 or PB12?

The PB12 information is too large to post and I wouldn't anyway.

[4313B]

L220A and L222A

[Hofmannhp]

Originally posted by Donald
............I plan to resolder the amp and I will clean off the flux.
.......

Hi Donald,

I wouldn't resolder the amp....the brown stuff is a special, well isolating, elastic (when fresh) glue for the mechanical reinforcement of the caps. It is often used for bigger parts to stabilize them on the PCB.
It is also used for transformers to reduce their magnetostriction, which often produces hum and other noise.:yes:
I recomend....close the amp, so you can't see it.

HP

[boputnam]

Originally posted by Hofmannhp
I recomend....close the amp, so you can't see it. :rotfl:

And, thanks, Giskard! The library builds... :coolness:

But, Donald, I'm not more clear on

"the black speaker wire was on the + post and the red on the - "

comment. Can you elaborate, or are you going mad as a hatter from sniffing all that solder... :eek:

[Donald]

The black wire from the speaker was connected to the spade lug on the PCB labeled + and the red wire from the speaker was connected to the spade lug on the PCB labeled -

I plan to resolder the amp as that is the suggested fix to eliminate motorboating. Which this unit does even when there is no input signal.

[Don C]

It looks like they have made the board with two different sizes of spade lug so that the phase cannot be mixed up. I think that you have a phase switch on the back panel anyway.

[Donald]

Don C,

You are right. On reassembly I see the connectors are different widths.

[Donald]

I resoldered. No motorboating for over 48 hours.

[Donald]

Spoke too soon. After reassembly I used the sub while watching Sopranos and Deadwood. Worked fine. Tonight I noticed the standby lights were off. Opened unit and 2A slo-blo fuse was blown. Installed another and it blew right after I turned on the unit.

I have given up. Trash day is Friday.

Suggestion for another sub??? $500 or so?

[Don C]

Rip out all of the crappy electronics from your JBL and put in a Parts Express plate amp.

[Alex Lancaster]

Before You rip out anything, go to the JBL site, contact customer service; I had a similar problem, if it is under warranty, You´ll probably get a new one, if it isn´t, like in my case, they gave me a good deal on a new one.

[Donald]

Don C,

Found the Parts Express site. What model amp would fit in the slot? Or would cabinet mods be needed?

[Don C]

Did you call JBL and make a fuss yet? They definitely know about the common problems with that sub, they might just ship you another one for free, like Alex said.
I doubt that you could do the amp change-out without doing cabinet modifications. You would want to get out the tape measure and see what size the opening for the amplifier is now. If you are not handy with the drill and saber saw, maybe it would be best to cut your losses on that sub, and get rid of it. (Get a Velodyne next time) But if it were me, I'd make an attempt to fix that PB12. You would want a plate amp that is bigger in all directions than the hole on the back of the sub cabinet, since it is easier to remove the material than to put it back.
Look at this one:
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=300-804

[Donald]

I have not called. I did not buy from an 'authorized' dealer. Which seems inportant to their registration site.

That amp is 10x10. The current hole is 12" tall. A match made in heaven it ain't. :)