Another wierd one. When is a T/S plug not like another T/S plug?

[nevetslab]

A Fender Twin Reverb came over with the complaint that the speaker jack is intermittent, mostly won't work. It's one of the infamous molded right angle T/S 1/4" phone plugs with the other end attached to 0.205" quick disconnect terminals attached to the pair of Jensen speakers. To get the speakers to work, you have to push on the plug. Having been down this road before, I grabbed one of my T/S to dual banana adapters (Pomona part, uses Switchcraft T/S plugs), and connected that cable to my test speaker. Amp jack works just fine, can't make it cut out by yanking and pushing on it in any way.

So, I chopped off the molded plug, and had one Amphenol right-angle T/S plug on hand, prepared the ends of the thin zip cord and slipping the cover and clear sleeve onto the cable, soldered the plug onto the speaker cable, squeezed the cable clamps into place, and threaded the cover onto it, and connected it back up. Switched the amp back on, and it seemed to work, so put the upper rear panel back on. Powered back out of S/B, and now it's NOT working without pressing onto the body of the plug. HUH? Unplugged that, reached for the other speaker cable plugged into my test speaker, and again, can't make it fail. I tried another cable....Switchcraft 280 plug at one end, Pomona MDP dual banana plug at the other end, connected a mating female to clip leads, attached to the speaker, and plugged that in. Worked solid, unable to make it misbehave. Tested the newly made cable with the Amphenol right angle plug, and can't make it misbehave. What makes a plug not work? Fender uses Switchcraft Type 12 T/S jacks with normal (to short it out if no plug is inserted).

OK, removed the mounting hardware that holds the chassis into the cabinet, and slid it out enough to look at the output jacks. Plugged in a Switchcraft 280 plug, and the normal is no longer shorting to the Tip arm. Removed that, plugged in the Amphenol plug. The Normal remains in contact with the Tip arm! What???!!! Pushing on the right angle body was enough to lift the Tip arm from the normal. Ya gotta be kidding me!! Fetched the needle nose pliers, and bent the Normal contact away and re-shaped it so it would short if no plug of any type is inserted, but with either of these plugs inserted, it lifts the normal. Looked at the tip shape of the two plugs. At a glance, looks the same, but obviously not for this jack to pull this nonsense on ya. Sigh............

[Enzo]

It was maybe 10 years ago, but I got a run of new from the box Fender HR DeVilles (Or was it HR Deluxe ?) Intermittent output. I found I had to reform (as in bend) the cutout contact on the speaker jack. The molded speaker plug tip wouldn't open the contacts far enough unless you leaned on it. A 280 or a 228 plugged in just fine, but not the stock plug. Fortunately a tiny bend with my duckbill pliers fixed each in seconds.


I never had run into issues before, but I had been aware of tip shapes for many years. I had a bunch of surplus brass plugs I really liked, but I noted the tips were more spsherical than the somewhat pointy Switchcrafts.

[drewl]

I find many of those molded plugs intermittent after years of abuse.
Just ordered another dozen metal right angle plugs.

[Leo_Gnardo]

Those molded plugs are poison. Any suspicion of misbehavior, OUT! And sometimes I'll get rid of one on general principles. Phooey! FEH!

Haven't tried any Amphenol quarter inch plugs. I think I won't ever bother after reading your tale of woe Nevets.

Just today had to replace a compromised angle plug on a 1979 Deluxe Reverb. Used a Switchcraft 228. Flat enough to not stick out beyond the box, unlike the 226. A PIA to solder to. Expen$ive too. But they do the trick. No dimension funnies when plugging Swcr plugs into Swcr jacks. The way life oughta be.

A long time ago, 1987, our esteemed FOH mixer asked me "are the dimensions of quarter inch plugs the same from brand to brand?" I told him hell, no. And I happened to have a micrometer handy to measure shaft diameter an a couple types we had ready to hand. Last was an expensive Monster Cable gold plated wonder. "You know why I never use this cable matey? Because I have to practically hammer it into the jack. We have a tour to do, I don't have time to replace busted jacks from trying to use this overrated gold plated CRAP." Indeed the diameter was a tad bit larger than any of the others we tried, Switchcraft and Neutrik. I still have that cable. I never use it.