Broken input jack on Studio 22

[alistair]

Hey guys,

I'm in the middle of getting a Studio 22 back up and running. It had some blown filter caps causing phasing/distortion on low notes, and also a large level of hum. I've replaced the caps which has cleared up some hum and distortion, and I think I've found the source of the rest of the hum.

A wire has come loose on the input jack, and I believe it's causing a grounding problem. I've attached two pictures to this email, so hopefully you can see it. The jack is a shorting jack, so when there is no lead in it, this tab appears to go to ground, and when a lead is inserted it breaks this connection to ground. Anyway, it's not mentioned in the schem and I haven't seen a similar jack in the Boogies I've worked on before, so I'm unsure where it should go. Any ideas? I'm assuming it's a ground wire of some sort, but separate from the other grounds on the input jack.

Thanks in advance.

 

[bigbean]

Could have been a repair/mod?
:?

 

[alistair]

Possibly, but I doubt it. It matches (in appearance) the footswitch jack and seems legit. I'm assuming it's there to short the input jack for silent removal of leads etc, I'm just a little confused as that is usually done by shorting the tip, not some ramdom extra tab!

 

[skizziks]

Looks exactly like my .22+. Don't think its a mod. Regards, Skizziks

 

[alistair]

Cool, thanks for the reply. Do you know where it should attach to? I'm guessing it's come sort of 0v ground rather than chassis ground, but I really don't have any idea.

 

[skizziks]

It appears that yours was originally soldered to the chassis next to the mounting hole. Get a big iron and apply plenty of patience. Sorry for the late reply. Regards, Skizziks

 

[alistair]

Thank you! That's worked perfectly. Kinda cool, I guess when the jack is unplugged it sends everything straight to chassis ground so it's quieter.

Amp is happy again and sounding great. I'm really impressed with the bass response too- as well as clearing up the distortion, the amp certainly sounds a lot tighter and focused in the bottom end.