Ampeg SVT-2 speaker jack stuck, melted!?

[JackANSI]

Newsbump, finally got there. Fuse is lower than given rating, and the plastic end of plug has melted around the tip of the jack. Kinda lousy cam pic, but should give a good idea..
Gonna get it to service, but any ideas on what might have gone down? Could there have been a continuous bad connection between tip and Jack that has caused the tip to heat?

I don't think it was mentioned but I think you're right. Could have been a poorly fitting 1/4" plug (or a really worn 1/4" jack) and the vibrations could cause inconsistent contact and cause it to heat up.

With your rehearsal supposedly "loud" I imagine the noise made by this could have easily been covered up by overdriven guitars (or if you use a lot of overdrive) and your ears losing sensitivity. It might have even happened fast enough that the jack melted and actually caused it to make better contact and then cooled down locking the plug in over the course of one song.

 

[Ruddwijk]

Thanks for the help. Was what I thought of and mentioned in the original post ☺

And yes, I do encourage plugs, worn them to rehearsal for 15 years. I don't, however discourage still playing loud!

 

[murphy]

Pardon? Seriously though, I won't go near a snare drum without my ER15 musicians' plugs in.

There are some really dodgy 1/4" jacks out there - even the likes of Monster do strange things with them, doing oversized plugs 'for better contact' which actually break sockets (as I found to my cost...)

I had numerous bass ....amp...and pedal problems because of those stupid spring loaded Planet Waves jacks

I refuse to wear ear plugs...and if the drummer is playing so loud to require that....I have fired the drummer....or quit the band

I am too old to risk my hearing

 

[Bassamatic]

Well - there is likely nothing inside the amp that could have melted - the plastic of the plug is outside and the jack and plug are metal and phenolic. I don't think that Ampeg would use a plastic jack for a speaker out, would they? And - if it did get that hot, this proves the point that 1/4" plugs and jacks are a poor choice for speakers.

The tip bending and jamming the plug is the most likely case, but is seems strange that it won't even twist. It is also strange the the Speakon isn't working. I hope you will let us know what is found when you get it in for service.

 

[agedhorse]

Well - there is likely nothing inside the amp that could have melted - the plastic of the plug is outside and the jack and plug are metal and phenolic. I don't think that Ampeg would use a plastic jack for a speaker out, would they? And - if it did get that hot, this proves the point that 1/4" plugs and jacks are a poor choice for speakers.

The tip bending and jamming the plug is the most likely case, but is seems strange that it won't even twist. It is also strange the the Speakon isn't working. I hope you will let us know what is found when you get it in for service.

No, that's not how it works.

Under say a 10 amp load (that's 400 watts at 4 ohms), if the contact is dirty, damaged, bent or loose, the point contact resistance will increase and say if the resistance increased to only 0.1 ohm, the power dissipated at the point of contact will be 100/.1 = 10 watts which is plenty enough to melt the plastic insulating sleeve inside the 1/4" plug (and it happens, I've seen it a few times). This can happen to ANY connector, though SpeakOns contact assemblies are better protected and much more robust.

I agree that 1/4" connections are not ideal for speakers, but for lower powered amps the track record has been pretty good over millions and millions of connectors.

 

[Foz]

OTOH the track record for truly filthy connectors is pretty sad regardless of make or model.

 

[Ruddwijk]

Well - there is likely nothing inside the amp that could have melted - the plastic of the plug is outside and the jack and plug are metal and phenolic. I don't think that Ampeg would use a plastic jack for a speaker out, would they? And - if it did get that hot, this proves the point that 1/4" plugs and jacks are a poor choice for speakers.

The tip bending and jamming the plug is the most likely case, but is seems strange that it won't even twist. It is also strange the the Speakon isn't working. I hope you will let us know what is found when you get it in for service.

Well, as i wrote a few posts up, i opened the back and the plastic covering the tip of the jack has indeed melted. Kinda hard to get a decent picture with my mobile camera (which is all i have available at the moment), but i can try and get a proper picture up if its of interest? The plug is of this sort: http://unbrokenstring.com/wp-content/uploads/2015/01/Ampeg SVT-200T Bass Head/09-jacklove.jpg