#1
I bought a second hand Mesa Boogie Lonestar 2x12 and realised that the tube on the far left, the 5U4G (see picture 1), is missing. This amp has been in use in a store for quite some time, hence I am wondering whether this missing tube could have had any negative effect and caused some damage over time.

Secondly, on picture 1 are also listed V1-5 and on picture 2 what it looks like inside the amplifier. Is there something missing as well?
Attachments:
1.jpg
2.jpg
#2
That amp has a switchable rectifier, yeah? Well it must be on solid state rectification. I wouldn't think it would hurt anything.

Explosive Cat and the Mystery of the Missing Tube
"If you're looking for me,
you better check under the sea,
because that's where you'll find me..."
#3
IF you have switchable solid state rectification, I would stick with that.
As long as the amp works.
Tube rectification, at least in an AC30 is a very fragile thing.
IN the case of the AC30, using the standby switch actually shortens the live of the rectifier tube.

Wait for others to answer or gimme about 6 hours to get some caffeine in me and get some other thins done like hunt a done schematic and I could tell you more.
Last edited by CodeMonk at Dec 25, 2015,
#4
Oh, what a wonderful title for a movie, DeathByDestroyr – you could play the Missing Tube.


CodeMonk, six hours have passed a while ago, where is your caffeine?


On the lonestar's rear side is a switch with the options 'diodes' and 'tube rectifier tracking', the former chooses solid state rectifiers, the latter the 5U4G. Since confusion is a state of mind I am usually in: 'tube rectifier tracking' uses the 5U4G and the four EL-34 (respectively 6L6) tubes while 'diodes' ignores those tubes but instead activates something called 'solid state rectifiers' (and are those V1 to V5 on picture 2)?
#5
Quote by Explosive Cat
Oh, what a wonderful title for a movie, DeathByDestroyr – you could play the Missing Tube.


CodeMonk, six hours have passed a while ago, where is your caffeine?


On the lonestar's rear side is a switch with the options 'diodes' and 'tube rectifier tracking', the former chooses solid state rectifiers, the latter the 5U4G. Since confusion is a state of mind I am usually in: 'tube rectifier tracking' uses the 5U4G and the four EL-34 (respectively 6L6) tubes while 'diodes' ignores those tubes but instead activates something called 'solid state rectifiers' (and are those V1 to V5 on picture 2)?

The SS diodes are internal on the PCB.

They have switched it to run on the diodes which isn't bad, but by simply replacing the rectifier tubes you will have the option of using both. The rectifier tubes give a more vintage spongy sound when you really dig into notes (like blues and classic rock)

It is hard to explain, but fairly easy to hear the difference. both sound good and have their place.
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
Last edited by Robbgnarly at Dec 26, 2015,
#6
Just to be sure: in picture 1 from my first post, 'diodes' uses V1-5 and 'tube rectifier tracking' uses 5U4G and 4x 6L6, right?

Secondly, if this amp has been in use with the wrong setting, i.e. 'tube rectifier tracking' with the missing 5U4G, what is the worst case scenario? That all the tubes are now kind of dead, or could other parts of the amp have been damaged as well?
#7
V1-5 are your preamp tubes, and the phase inverter. The diodes are just some little guys.

I don't see why it would hurt anything. I mean don't go around using it as a killswitch or anything, but it's not like somebody was sticking paperclips in there or anything.
"If you're looking for me,
you better check under the sea,
because that's where you'll find me..."
Last edited by DeathByDestroyr at Dec 29, 2015,
#8
I recommend this for all amps but especially Mesa - download the manual from their website and read it cover to cover.

Then sit in front of your amp and read it cover to cover again.

Repeat every so often.

For the Rectifier tubes on my Roadster they are only used when the the switch is set to tube. I have a switch for each of the 4 channels. 2 5U4G in 100W mode and 1 5U4G in 50W mode again all per channel.

I'd recommend putting a 5U4G in there just in case the switch gets flipped by accident. You may also really like the sound. Might as well get everything out of the amp you can.
Guitars:
Ibanez RG1570 Prestige
Jackson Kelly KE3 - MIJ (Distortion/Jazz)
Jackson DKMGT Dinky (EMG 81/85)
ESP E-II Eclipse Custom (JB/'59)
ESP LTD EC-1001FR (EMG 81/60)
Fender MIM Strat

Amps:
Mesa/Boogie Dual Rectifier Roadster 212
Laney IronHeart IRT-Studio
Peavey Vypyr 30
Peavey ReValver Amp Sims
TOOOO many T.C. Electronic Pedals. . .
#9
mesa has switched over to the g4B which is a shorter tube then the old g4 on their newer amps but you can still buy coke bottle g4's for like $40 online. i would probably just email mesa for clarity and then go pick up whichever one they recommend and will fit within the chassis.