More amp problems! Yay!

[Black Mariah]

I think I blew up my Sunn (!). During practice a couple of weeks ago, it started making a weirdass high-pitched noise. I turned it off for a while and it worked when I turned it back on. I assumed it had got a little too hot or something and chalked it up to the foam I had underneath it to keep it from rattling off of my cabinet. I get to practice today and fire it up... *SQUEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEAL* If I get the master volume up to 7 or so, it starts to squeal. If I have the right EQ dialed in, it squeals. Here's where it gets weird. If I unplug the guitar from the amp, it stops squealing.I have used several cables, guitars, and cabinets with it and it has never done this. The only good thing I can think is that Sunns are composed of about 12 parts and all are easily replaced. If anyone has an idea, I'll rip this thing apart and poke around (with a PLASTIC poking device, of course) and see if anything looks melted.

[Hotrodder]

Re: More amp problems! Yay!

Sounds like a microphonic tube to me. Well if it's a tube amp that is.

[Black Mariah]

Re: More amp problems! Yay!

If it was a tube amp, that would have been my first thought, but no. Sunn Concert Lead. Solid state as it gets. Maybe a microphonic IC? If it overheated, it very well could have blown a chip or something.

[buzzsaww]

Re: More amp problems! Yay!

sounds like maybe a cold solder joint?

[charvelguy]

Re: More amp problems! Yay!

most likely an input jack or a jack related problem since the condition doesn't exist outside of plugging it in. I would say rather safely, it's not a major deal.. hopefully I'm not wrong here. if it makes noise of any sort, I would say the tranny's are still kickin, so the "blown up" isn't an issue. if it were a major problem or a chip, the fuse would be long gone.
It's in the jack, or a signal short in that area OR something has slipped out of tolerance...I'm almost positive.

[ April 27, 2003, 10:03 AM: Message edited by: charvelguy ]

[Black Mariah]

Re: More amp problems! Yay!

Okay, even more f**ked up stuff. I turn it on earlier and I'm greeted by a loud-ass NOISE. It sounded like speakers farting whenever you throw too much bass in them. I thought my speakers we going to explode and pepper my nether regions with little pointy speaker bits, so I turned it off and didn't bother turning it back on. This is with nothing plugged into it, too. [img]images/icons/frown.gif[/img] I think a trip to a tech is in order. [img]images/icons/mad.gif[/img]

[Newc]

Re: More amp problems! Yay!

Yep. Sounds like you got a problem. Are your cables in good shape? Could be you got a loose/bad connection in either the cables (guitar and/or speaker) or one of your amp's jack wiring is bad/broken?

Newc

[Black Mariah]

Re: More amp problems! Yay!

It's definitely not the cables. I've tried several and nothing helped. Hell, it might be the jacks. I'll get it over here and pull it apart and see what I can do with it. I understand that solid state amps are slightly less deadly than tube amps, so I don't mind poking around in them with a metal poking device. [img]graemlins/poke.gif[/img] [img]graemlins/laugh.gif[/img]

[charvelguy]

Re: More amp problems! Yay!

well, if we don't hear from you again, we can assume a capacitor discharge probably killed ya.
(bad joke, I know) Be careful. [img]images/icons/grin.gif[/img]

[OnlineStageGear]

Re: More amp problems! Yay!

The most common failure in electronics, especially any circuit involving heat despersion of any sorts, is loose solder connections, more commonly refered to as a "Cold Solder Joint"

Instrument amplifiers and PA gear is even more prone to it due to the fact that when you shut the amps off at the end of the evening, it is still warm inside and warm solder is always softer, then you chunk the gear in your hatchback and go jump the railroad tracks on the way home, busting things loose.

Matt

[Twisteramps]

Re: More amp problems! Yay!

Couple of tips, off the top of my head...

take some wire and a 10k or so resistor (1 watt if ya got it) and put the insulated wire on either end of the resistor. Solder it, and cover any exposed areas except for the ends with electrical tape. Now take this, and look for large capacitors. When ya see em, touch one end of your wire/resistor tool to the amp chassis and the other end to the positive end of the cap. this will discharge it. Do this for EVERY large cap you see in the amp - shouldn't be a lot of em. Another thing you can try is just unplug the amp and turn it on, leave it on for a minute or two.

Now take a drumstick, sharpie, etc (The idea is something non conductive) and poke/prod things on the circuit board like resistors, wiring, etc. Don't pull stuff loose, but check em to see if they are still tight. If they aren't... resolder the connections. Also look for any burn marks or damaged components.

If you really want to make sure, reheat all the solder joints, especially if you see any dull ones that aren't shiny.

Pete

[Black Mariah]

Re: More amp problems! Yay!

Thanks for the tip on discharging the caps. I wasn't sure how to go about doing that. I have a feeling I'm going to end up reflowing all the solder joints. This thing's about 25 years old so by now even the shiniest of solder joints would have tarnished or corroded, or whatever it is that solder does. [img]graemlins/laugh.gif[/img] I'll get around to it this weekend, most likely.

[ColdVayne]

Re: More amp problems! Yay!

Just re-solder everything [img]images/icons/grin.gif[/img]

[ColdVayne]

Re: More amp problems! Yay!

Try opening it up and looking at the soldering sometimes it might come loose. Also see if you can use the exact stuff you are putting into the amp ( cord , guitar etc ) into another amp and see if it does it. If it dont then look at the fuses cause it might be a busted fuse because i had that same problem with one of my old valvestate marshalls.

[ April 29, 2003, 12:04 PM: Message edited by: ColdVayne ]

[Wayniac]

Re: More amp problems! Yay!

My bassists rig was doing the same thing. Turned out to be a loose wire on one of his speakers, grounding out to the frame on the speaker. Ended up frying his amp head and blew the fuse on his Eden 4X10. Luckily Carvin took good care of him, and replaced and cleaned the entire head.. all for the cost of shipping.
You can try to "ohm" out the cab to see if that is your issue....