Dual Recto, strange noise

[bryan_kilco]

At practice last night, other guitarist fires up his Dual Recto and it is making strange noises. It sounds sort of like tube failure, but not really.

It's hard to describe. When the amp is flipped off of standby, it takes like 5-10 seconds before the sound starts happening and it happens over both channels. We swapped guitars, took everything out of the chain in front of the amp, problem remains. I lightly did the old tap test on the tubes but found no power tubes that were giving any signs.

Pretty sure these tubes are a high gain set of JJ's from Dougs Tubes that are about 4 or 5 years old now. So it's probably time for a change anyway, but the sound that comes through is unlike the tube noise I've heard before.

Its like a fizzy/crackling that is constant. When I heard tubes going bad in the past, it sort of sounded crackly but the sound would sort of come and go if you tap the tube/top of the amp....and you could hear the slight loss of power. With what we experienced last night, I'm left scratching my head.

 

[53Crëw]

Probably 90% of tube amp problems are from a tube going bad. Take a spare 12AX7 and swap them out one-at-a-time until you find that bad tube.

Tubes can fail in all different manners. Sometimes it's intermittent, and sometimes not.

 

[bryan_kilco]

Yep, that's the plan next practice. Though I've never experienced a preamp tube going bad. Isn't their life expectancy something like 5-7 years?

Although I have heard stories of people getting bad tubes right out of the box.

 

[53Crëw]

I've had some last 10+ years. I've also had a few fail me within 3 months by getting crackling noises or volume cutting in and out. Some brands are more prone to occasional failures than others.

Also, just FYI - Mesa doesn't recommend running Russian tubes in the V3 and V4 positions. I don't recall whether or not there's problems with JJ's specifically, but I know I had an EH or Sovtek tube fail in that position. It seems some of them can't handle the voltage. Might be safest to run a Chinese tube in those spots, per Mesa's recommendation.

 

[BLUElightCory]

Just change out all of the tubes. It's time.

The fact that the amp takes awhile to get going after coming out of standby makes me think you've got power tube problems (not to mention the tubes are 4-5 years old, they're WAY overdue to be changed).

 

[greyskull]

That sounds like a tube had failed and has taken a resistor with it. Open her up and look underneath where the tubes connect on the board. There's a bunch of resistors there, one of which is probably fried

 

[bryan_kilco]

Oh boy. Well, I'll try swapping a good tube and see if it fixes it. I'm not all about opening up the amp. Only did that a few times and poked around in there, and this was back before I knew that the caps held evil chargers for quite some time!

 

[bryan_kilco]

Well, this weird noise just went away so we couldn't exactly troubleshoot it.....go figure!

Now the other guitarist is going to the Bahamas to get married and we won't be able to get to our gear for 2 weeks. Luckily I brought home a mic and some stuff to mess with reamping.