Volume drop on Roadster

[jhguitar1]

I let my Roadster warm up, turned off the standby and everything was fine for about 30 seconds and then I lost about all of the volume of the amp. I can hear myself playing if I turned it all the way up and even then you can barely hear it. Any suggestions? Tubes are new. Can they be the problem?
Thanks for your help.

 

[jamme61]

could be something stupid, do you have kids? I do, and sometimes they can't keep away from all those dials on there. check all those masters on there and your cables and then look at all the tubes, while on stanby, are all lighting up? Try going to diode instead of useing the rec tubes(could be a bad rec tube) if power tubes,rec tubes, masters are all good, try the 12ax7 preamp tubes(one at a time) Good luck i hope it's something small, like the kids LOL.

 

[123thefirst]

That sounds like what would happen if you were actually in Standby mode. You should power up with the Standby switch down and then raise it into the High Volts position after a minute or so, right? Are you sure that things didn't get a little confused at that moment? (Mesa has re-labeled the Standby switch at least once apparently because it was confusing)

 

[domct203]

I let my Roadster warm up, turned off the standby and everything was fine for about 30 seconds and then I lost about all of the volume of the amp. I can hear myself playing if I turned it all the way up and even then you can barely hear it. Any suggestions? Tubes are new. Can they be the problem?
Thanks for your help.

Does this happen in all 4 channels? Could just be a bad preamp tube.

How's your speaker cable? Instrument cables, etc.? Check them all out. Just swap out one thing at a time until you find the problem.

Try Hard Bypassing the loop and see if there is any change. I had the same thing happen to me and it was a bad tube in V4 (the tube had actually cracked). Carefully take the shields off your pre-amp tubes and visually inspect the tubes. Any tubes that have a white instead of silver top have to go. If all looks fine try replacing the preamp tubes one at a time with a known good tube and see if the problem goes away.

Good Luck.

Dom

 

[123thefirst]

(duplicate message)

 

[jhguitar1]

I was reading in the manual on pg. 23 that the problem may be a driver tube. Which tube is the driver tube?
Everyone has been great and I appreciate all of your advice!!!

 

[lyman]

check out the effects loop: you can put even just a short connecting cable from the fx send to the return. for some reason, some mesas have a problem when you're not using the loop, the volume can drop out. so try putting something in the loop before you buy new tubes. it takes 5 seconds.

 

[Sling Blade]

just like he said above. My 550 used to do the same thing. Put a patch cable in the FX loop. Fixed it like a charm.

 

[jhguitar1]

Thanks for all the advice. Looks like it was the tube in the V5 position. Does anyone know what each preamp tube controls? The manual does not show that info.

 

[Storm]

I know that V1 is the first gain stage and V6 is the phase inverter. The reverb driver is there somewhere. Don't know the rest :?:

Ciao ...

 

[JAZZGEAR]

It's most likely (hopefully!) a bad preamp or output tube. possibly a rectifier tube but you can eliminate that by setting your rectification to silicon diode.

Try tapping on the tube with the eraser end of a pencil (lightly) when the amp is running. If you hear any strange sound it could be a bad tube.

Tubes go bad during shipment. Even though the amp is brand new, it could still be a bad tube...

Also try pulling the outside or inside pairs of 6L6/EL34 tubes and running in 50 watt mode. Be sure you know which output tubes are used in 50 watt mode (inside or outside, not sure). The impedance will change as well when you do this.

A full retube won't hurt but is costly...

+1, I just bought a brand new head...and had the exact same problem...and was about to return it when it ocurred to me to just replace the tubes.....and it was indeed the PH tube that was bad.

I ended up replacing all of the tubes with JJ Power and GT pre....for the sake of it...and the volume returned to normal.

It sounds great now..and loud...even in the 10 watt mode.

 

[domct203]

Thanks for all the advice. Looks like it was the tube in the V5 position. Does anyone know what each preamp tube controls? The manual does not show that info.

The Roadster Preamp tube functions are the same as the RKII.
V1 Input & Second Gain Stage
V2 Third Gain Stage
V3 Fourth Gain Stage & Tone Stack
V4 FX Loop
V5 Reverb
V6 PI

I printed out the tube task chart for the RK and slipped it in my Roadster Manual.
Don't know why Mesa did not include it in the manual though.

Dom