Bad input jack?

[JGR]

Hi all. Recently, I've been having a problem with my Ampeg SVT CL head; intermittantly, I have been getting a very bad static sound with the signal cutting in and out. It goes away at times, and sometimes is only present when really digging in and on the lowest notes. I've bypassed the preamp section and used the power amp with another preamp with no problems. Also replaced the preamp tubes and the problem still exists. I've switched basses, speaker cables, cabs, and inst. cables as well and it's still there off and on.

I'm thinking the input jack/ground is going bad as it comes and goes when I wiggle the cable in the jack. It all started when I was doing general maintenance with some Caig DeOxit in the jacks - go figure. I'm here in AZ so static is a real problem. The low input jack does it as well, but not to the same extent.

Any other suggestions/similar experiences before I replace the jack?

Cheers,

JR

[Tom Phillips]

JR,
Sounds like a classic case of a cracked solder joint at the input jack. I believe that the SVT CL design uses PC board mounted jacks. Sometimes there is a small ring crack around one of the jack pins which can be very hard to see. In most cases, re-doing the solder joints cures the problem without needing to replace the jack.
Regards,
Tom

[JGR]

Thanks Tom!

That makes perfect sense. I'll try reflowing the joints before I replace it.

Cheers,

JR

[Tom Phillips]

Even beter would be to use a solder sucker or solder wick to remove the old solder first then apply a fresh joint.

[Rob Mercure]

Why

Tom,

Why? Having done SLM warranty for a few years I routinely reflowed the solder joints on every warranty repair that came my way whether there were problems or not. Only took a few minutes and helped prevent call backs. But I never removed the old solder unless I was swapping a part. In fact I often added additonal solder to have more "mass" holding the jack or control in place. Not that it's gonna break your budget but removing the old solder and replacing it is wasteful (and solder is, by definition, hazardous waste) and makes for more time in the repair. The old solder isn't "bad" only crystalized.

Rob

[Enzo]

SLMs especially like to have their 10 watt cement resistors resoldered.

I agree, the solder doesn't need to be replaced. I touch a tiny bit of fresh solder to the joint to get some new flux, but that's about it. I suppose I could use some liquid flux, but why bother?