Roadster Problems :(

[guitarbloke]

Last night, about halfway through our set, my Roadster head suddenly lost about 95% of it's volume onstage. I still had some volume but it was negligible almost impossible to hear.

I had to power it off and back on again to get my sound back - it happened twice during the evening, but did eventually come back after being switched off for a moment.

Could this be a power tube issue? I bought the amp used and the seller told me he had never changed the tubes. I swapped a couple of the pre-amp valves a few weeks ago - but I haven't replaced the power tubes since I bought the amp.

I'm using a US model head with a step down transformer to run it in the UK if that makes any difference.

Any ideas what might be causing this? I'm quite worried about using it again onstage

 

[screamingdaisy]

What brand of tubes did you install?

New Sensor dropped their quality a few years back and now their tubes can't handle the voltages present in the cathode follower positions. Volume fluctuations are usually a sign that that they're on their way out.

On a Roadster the cathode follower is in the V3 and V5 positions. Make sure those spots are filled with either a JJ or Chinese preamp tube. Stock Mesa tubes are currently JJs.

 

[guitarbloke]

I only put 2 new pre-amp tubes in - a Tung Sol reissue in V1 and a Sovtek 12ax7 LPS in V6 - the rest of the tubes are the stock Mesa ones.

It was sounding beautiful until the volume went

 

[domct203]

You should check what tubes are in V3 & V5. My '07 Roadster came stock (new) with Mesa labeled Electro-Harmonix 12AX7's (Russian-2), a tube that has proven to fail (loss of volume/sound dropouts) in cathode follower use.

The Mesa "Russian-1" (Sovtek) and "Russian-2" (EH) are not recommended for cathode follower use.

Dom

 

[guitarbloke]

Thanks guys, will check what tubes I have when I get home today.

Does this sound more like a preamp tube problem rather than being power tube related?

 

[screamingdaisy]

Thanks guys, will check what tubes I have when I get home today.

Does this sound more like a preamp tube problem rather than being power tube related?

Sudden volume drops are usually preamp tubes.

Slow declines in volume/sound quality are usually power tubes.

Blown fuses are usually power or rectifier tubes.

 

[guitarbloke]

Thanks I'm a bit of a noob at this!

Ok,I've had a look, and this is what I have in my Roadster right now:

V1 Tung Sol Reissue
V2 Mesa Chinese-1
V3 Mesa Russian-2
V4 Mesa Russian-2
V5 Mesa Chinese-1
V6 Sovtek 12ax7 LPS

What's the most reliable option to replace those Russian Mesa's with? I was thinking of just going with some JJ's since they're dirt cheap - do you reckon JJ's would be a good choice? I hear EHX are good high gain tubes - would these be a better option?

Hmmm or would switching the pesky Russian from V3 with the Chinese from V2 be ok to do - or is the tube is likely to keep failing now that it's failed for the first time?

 

[screamingdaisy]

What's the most reliable option to replace those Russian Mesa's with? I was thinking of just going with some JJ's since they're dirt cheap - do you reckon JJ's would be a good choice? I hear EHX are good high gain tubes - would these be a better option?

You have to use JJ or Chinese. EHX is made by New Sensor and New Sensor tubes in the cathode followers will eventually fail. The ones that are in the V4 and V6 position should be fine. It's only the V3 and V5 spots you need to worry about.

Hmmm or would switching the pesky Russian from V3 with the Chinese from V2 be ok to do - or is the tube is likely to keep failing now that it's failed for the first time?

The tube is probably finished, but I've never experienced this myself so I can't say for sure.

 

[guitarbloke]

Thanks for all your advice, I placed an order for 2 JJ's last night, so will replace those Russians as soon as they arrive!

 

[guitarbloke]

Hmmm so my JJ's arrived, but their boxes say 'made in Slovakia' - I thought they were going to beChinese. does this seem right?

 

[bendo]

For JJs yes. Slovakia is one of the locations where they are manufactured.

 

[user 19273]

I had a similar issue & it turned out to be the DIN cable partially disconnecting from my footswitch!
I stood on it, and when I hit the solo button - nada!