Brand new rig turned to smoke

kurtthompson · #1 11-08-2011, 10:34 AM

I spent the last couple of months gathering my new bass rig

SVT II head
Ampeg pr410hlf

MXR Blowtorch fuzz pedal

Ibanez SR500

I played the head and bass together once and they worked fine, the cab has some noise but I got it used on guitar center for $200 so thats understandable

My newly repaired pedal arrived friday and I checked it in the shop and it worked perfectly

So i set up to use my new rig with my fuzz pedal for the first time at band practice. I had the head and cab hooked up at 4ohms each and my bass going into the pedal going into the "normal" input on the front of my SVT II

Once i had it all turned on the fuzz pedal wasnt bypassing and the signal was a little weak. I think i started tweaking the parameters of the fuzz pedal a bit and then suddenly the whole rig shut off and smoke came out of both sides of my SVT II

All were powered by the same power strip and the pedal was even going into a short ungrounded extension cable because the power adapter plug didnt fit into the strip

I dont have pictures or anything of the SVT and i just dont know whats wrong with it but i could really use some ideas

i'll take it into the shop later today but i'd love to know what comes to mind from you guys

Bassmec · #2 11-08-2011, 11:51 AM

Might be a massive DC offset from failed transistors in the fuzz pedal. Measure its output with a scope.

seamonkey · #3 11-08-2011, 06:15 PM

Ampeg has a 5 year warranty on brand new amps

Did you have the impedance switch right?

**B-string** · #4 11-08-2011, 07:49 PM

I hate it when the magic smoke gets out.

walterw · #5 11-08-2011, 08:43 PM

Quote:

Originally Posted by Bassmec

Might be a massive DC offset from failed transistors in the fuzz pedal. Measure its output with a scope.

no way in hell did a pedal cause the amp to smoke.

basslinejam · #6 11-08-2011, 08:52 PM

Downunderwonder · #7 11-09-2011, 01:21 AM

Quote:

Originally Posted by walterw

no way in hell did a pedal cause the amp to smoke.

I can imagine feeding DC into an amp input being unhealthy for the amp.

Stumbo · #8 11-09-2011, 01:23 AM

You might need this if your rig is not under warranty: Good amp techs!

vbchaos · #9 11-09-2011, 01:34 AM

Quote:

Originally Posted by Downunderwonder

I can imagine feeding DC into an amp input being unhealthy for the amp.

That SHOULD be captured at the input using a capacitor

will33 · #10 11-09-2011, 01:39 AM

Quote:

Originally Posted by walterw

no way in hell did a pedal cause the amp to smoke.

Not necessarily, I've got burned resistors in poweramps from putting way too hot signal in the front end.

OP, does your amp have a foul smell that doesn't seem to go away? That may be a burned white ceramic resistor. Those things stink strong for days. God-awful things they are.

craig.p · #11 11-09-2011, 05:00 AM

Quote:

Originally Posted by vbchaos

That SHOULD be captured at the input using a capacitor

Or if not at the input, by an early-stage coupling capacitor. I agree that DC offset is unlikely to have caused this.

Kurt, you said your cab "has got some noise." It's possible it was presenting some sort of weird impedance to the amp, and that weird impedance blew out the finals (output tubes, output transformer, resistors in the output stage, take your pick, won't know until someone goes in there and looks around).

staindbass · #12 11-09-2011, 07:12 AM

Quote:

Originally Posted by Bassmec

Might be a massive DC offset from failed transistors in the fuzz pedal. Measure its output with a scope.

great idea ! buy a $500 scope to see what the problem is, then take it to get repaired

AwkwardLoudness · #13 11-09-2011, 07:48 AM

What was the impedance setting on the SVT?

Ampeg PR-410HLF cabs are supposed to be 4Ω impedance. Did you check the speakers' wiring to see if that had changed? Were all of the speakers connected properly? A broken connection somewhere would cause the impedance to go awry and possibly induce noise issues.

pig · #14 11-09-2011, 08:24 AM

you say you bought yer cab used and it had some noise. the previous owner could have modded the cab and changed the ohmage to use with their head that may not have been he same ohmage. which could very well cause your problem.

I blew a little guitar amp the other day. when I opened it I noticed a little screw got loose fell out and shorted the filter caps. have you opened your head to see if anything was loose?

tech21nyc · #15 11-09-2011, 09:35 AM

Were you using a "speaker" cable between the head and cab or an "instrument" cable? An instrument cable between an amp and cab can easily overheat and blow the amp. It's also possible that a connection was possibly loose in the cab and if that happens and the amp is not seeing a load it will blow just the same.

basscooker · #16 11-09-2011, 09:47 AM

sorry no help just wnted to say i'm hoping it's not bad bad bad, and it's covered under warranty.

hope all turns out. do you have a backup/ scheduled shows? ukno i had a rig go down 2 days b4 a show once and discovered a neat amp only b/c i needed something in a hurry, so sometimes these things work out fine.

Alex1984 · #17 11-09-2011, 10:41 AM

Have you tested it out before buying? Is it an SVT 2 Pro or Non-pro? I'd suspect the cab being funky.

kurtthompson · #18 11-09-2011, 02:43 PM

Quote:

Originally Posted by tech21nyc

Were you using a "speaker" cable between the head and cab or an "instrument" cable? An instrument cable between an amp and cab can easily overheat and blow the amp. It's also possible that a connection was possibly loose in the cab and if that happens and the amp is not seeing a load it will blow just the same.

i was using a basic 1/4"... what's recommended? speakon? or another type of 1/4"?

Its an SVT II non pro

The head and cab were matched at 4ohms but i guess the previous owner could have modified it? i wouldnt have guessed that

there was no stink but i have a bad sense of smell... my bandmates didnt say anything though haha

edit* - you guys are awesome, thanks for all the replies - its rare to experience such interest when you have like 2 posts on a forum

I'll be sticking around here for sure

ack · #19 11-09-2011, 02:50 PM

Quote:

Originally Posted by kurtthompson

i was using a basic 1/4"...

I think this may be at least part of the cause. I was warned to never use basic 1/4" instrument cables between the head and cabs.

I'm new to amp/cab, so I'll be waiting to hear the more knowledgeable guys chime in.

tech21nyc · #20 11-09-2011, 04:23 PM

Quote:

Originally Posted by kurtthompson

i was using a basic 1/4"... what's recommended? speakon? or another type of 1/4"?

Its an SVT II non pro

The head and cab were matched at 4ohms but i guess the previous owner could have modified it? i wouldnt have guessed that

there was no stink but i have a bad sense of smell... my bandmates didnt say anything though haha

edit* - you guys are awesome, thanks for all the replies - its rare to experience such interest when you have like 2 posts on a forum

I'll be sticking around here for sure

It's not a matter of 1/4" vs speakon etc. It matters if it was a speaker cable vs instrument cable. There is a difference. It sounds like you may not know what the difference is. I learned the hard way many years ago with an old Kustom bass amp. I used a flimsy instrument cable and after a few minutes the amp blew.

Here is some info:
Cables 101: Instrument vs. Speaker Cables