Help me retube a Roadster 1x12 combo

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gribbly

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Hi all,

First post to the forum. Apologies if I break etiquette out of ignorance - pls correct me!

Anyway, I just bought a second-hand Roadster 1x12. The age/condition of the tubes is unknown to me. This is my first Roadster, so I don't have a direct comparison (although I've owned an Express 25+ for a while, and know it well). I play a Fender Deluxe Strat with N3 HSS pickups.

The problem I'm having is that channel 2 sounds very flat and dead.

Channel 1 sounds good but not great (could just be that I haven't got it dialed in yet)
Channel 3 sounds *amazing*, I am already addicted to the crunch I'm achieving.
Channel 4 sounds great too.

Compared to 1,3 and 4 channel 2 sounds really weak and thin and cardboardy. I'm assuming it's old tubes.

Here's my question: How would an experienced Roadster owner go about re-tubing this amp? I have budget to completely re-tube the thing (and in fact have ordered the tubes to do so from Mesa Boogie, they should arrive mid-week). But I want to learn to do it right, and I want to save any good tubes to have in hand as spares.

So I'm after recommendations to how to proceed with the re-tubing. Pre-amp tubes first? In what order? My initial thought was to try and locate any pre-amp tube(s) specific to Channel 2, but I get a little confused when I look at the tube replacement chart (p37) in the manual. I see one 12AX7 in the V1 position. But then the table says:

V1A - Input Stage
V1B - Second Gain Stage

What is V1A and V1B? AFAIK there's only one tube in position V1... so what is A and B?

Similarly, there's a V2A (CH 1/CH 2) and a V2B (CH 3/CH 4)... is that one tube or two?

Should I be replacing V2 first to see if it revives Channel 2?

Should I just go ahead and re-tube the whole **** thing (5U4Gs included) and just get it over with?

Should I be looking at the 6L6s first?

Thanks in advance for any help/insights.
 
V1A/V1B refer to different sections of the same V1 tube.

I love regular Tung Sol's. I also find them to be good in almost all positions.

Mixing and matching tubes will probably give you a more noticeable effect when using low gain tones.

I play mainly high gain stuff, so I just stick with all Tung Sol's.
 
Yeah, 12ax7 tubes are dual triode so one tube controls 2 functions. So the channel 1&2 tube may be the culprit. You can switch it with a different tube to see if you hear any changes.
 
Thanks, that's exactly the info I needed!

EDIT: Woah, what a difference. I swapped out the tube in V2 with a new 12AX7 (a J&J I got from a local guitar shop) and Channel 2 has come alive... tone for days. I just sat there noodling for 1/2 an hour because I couldn't stop!

I'm still uncertain on whether a full re-tube is warranted. The amp sounds great to me now... I guess I should just wait until it needs it to swap any other tubes?

I have all the tubes coming (I figured it made sense to have spares anyway), and will switch out the J&J with the Mesa 12AX7 when it arrives (I want to stay stock). But I'll hold off on replacing the power tubes or any other tubes until I hear a reason to do so.

Hmm, I guess I could try temporarily switching in the new power tubes just to A/B, in case it sounds heaps better and I just don't know what I'm missing...
 

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