EDIT: Bad pot made me think my 077s were distorting

[Zonker92]

I believe they are film caps. I have heard that over some decades their ESR may rise, but perhaps that would attenuate their output, not make it harsh.

 

[Mr Boochie]

Do the N333 caps generally go bad? I have debated re-capping, but after a ton of searching didn't find many / any discussions talking about out-of-spec caps in these networks. Are they electrolytic in there?

I believe that the only way to know for sure, is pull the 077s and the crossover networks and have them bench tested. If you live in West LA, I strongly recommend Bao, at Speaker Repair Pros. Just a drive down the 405 to the 22 to Brookhurst. He's the most knowledgeable JBL tech in So Cal.

http://www.speakerrepairpros.com/contact-us.html

 

[Johnny_Law]

Finally got these in the garage to test them more closely ... I was mistaken before. The distortion is coming through the LE85s, not the 077s.

• Turned the LE85s all the way down, and 077s all the way up. No distortion.
• Turned the LE85s all the way up, and 077s all the way down. Distortion.
• While the song was playing, turned the LE85s down & up and listened. Distortion went away, came back, in and out. Worse on one side than the other.

So ... I will pull the pots back out and take another look. I already cleaned / sanded them once, maybe I failed at putting them back together, or maybe I just need to replace them.\

I never put the foilcals back on after I painted the baffles, so don't have to deal with that.

Breathing a sigh of relief that it doesn't look like I have to pull the 077s apart. Fingers crossed.

Side note, playing that song from my first post in the detached garage, loud to listen to distortion, caused the entire little building to rattle. LOL! 136As are fun.

 

[toddalin]

Finally got these in the garage to test them more closely ... I was mistaken before. The distortion is coming through the LE85s, not the 077s.

• Turned the LE85s all the way down, and 077s all the way up. No distortion.
• Turned the LE85s all the way up, and 077s all the way down. Distortion.
• While the song was playing, turned the LE85s down & up and listened. Distortion went away, came back, in and out. Worse on one side than the other.

So ... I will pull the pots back out and take another look. I already cleaned / sanded them once, maybe I failed at putting them back together, or maybe I just need to replace them.\

I never put the foilcals back on after I painted the baffles, so don't have to deal with that.

Breathing a sigh of relief that it doesn't look like I have to pull the 077s apart. Fingers crossed.

Side note, playing that song from my first post in the detached garage, loud to listen to distortion, caused the entire little building to rattle. LOL! 136As are fun.

Possibly (definitely if original) the foams in the rear caps have rotted and some may have lodged against a diaphragm in moving the cabinets. Other than a dirty pot, this would be a best case scenario.

 

[Johnny_Law]

Possibly (definitely if original) the foams in the rear caps have rotted and some may have lodged against a diaphragm in moving the cabinets. Other than a dirty pot, this would be a best case scenario.

Been thinking about this for a while. These LE85s are original, never opened, and had a stint in my L200Bs previously, where they sounded great but I have been wondering if the foam will ever be an issue ...

 

[Johnny_Law]

Turns out it was a single mid pot, I adjusted it to a clean spot and listened for the last hour, sounds great now. My left ear is hard of hearing for certain frequencies thanks to an ear drum injury when I was a kid, so this kind of thing is really hard to me to diagnose by listening.

Edited the title.

 

[Jenkster]

I figured it was an L-pad, glad you were able to track it down.