Rediscovering my Mark III 6A 300 Series / SN help?!?

[hughjass]

Greetings. I recently dusted off my guitar equipment after a prolonged "hiatus from the free world" and am loving the rebirth. I am getting the gist that my Boogie is kinda rare. I have a Mark III Simul-Class 6A 300 Series blue stripe head with a 4X12 (2 Celestion,2 EV). It has the initials MB on the back and the date 3/89 on the inside. I saw on a website that the SN should fall between K423-K500, and may be one of 78 made. Problem is, after carefull inspection, I cannot find a serial number anywhere. Anyone have some advice?

Also, after long storage I find all the power tubes are 6L6's, without any EL34's. Not to mention I am missing a power tube. Socket #5 is emtpy. I've been playing it about a week before noticing the missing tube. The tone is not what I remember and it has a crackle so I am looking at replacing tubes but I am pretty broke. How does the missing power tube affect things, and how much difference will swapping in 2 EL34's make? I am also going to replace at least the preamp tube in slot one.

Any comments, questions, advice are welcome. Thanks

 

[Jim Ed Love]

I would change all of the tubes. I know it can be expensive, but well worth the tone.

 

[guitarzan1143]

When i got my mark iii it had all of the original tubes, 4 6l6s. It sounded like crap. I put two new mesa 6l6s in the middle slots, and two ruby el34s in the outer slots. my god what a difference. as for preamp tubes i used 3 or 4 different kinds, but the important ones are just plain EHX 12ax7s. i found them all for under 10 dollars a tube, picking them up on craigslist and ebay, all of them are new.

 

[Elpelotero]

If the amp is not simul-class, I would suggest NOT using any el34's unless you really know what you're doing. Otherwise something will burn up for sure, or at the very least, the tubes will not last long and your money will be ill spent.

The serial number should be imprinted in the back near output jacks for speaker cables.

 

[hughjass]

Thanks Elpelotero. Not sure how I missed that. My S/N is 24619. I can't believe I didn't see it last night even though it is still black despite the stamp. My amp is simul-class. I have the 300 series mark III with 6 power tubes. From what I see on the Boogie site owners manual, the two EL34s go on the outsides instead of the middle with this model. Am I reading that right?
Also I see places like the tubestore.com sell full sets of replacement tubes for a discount, but I would like to stick with Mesa tubes. Anyone know of a place I can get full sets of Mesa tubes and get the full set discount?
I'm still trying to remember what happened to my #5 power tube. Guess my priorities were elsewhere when my tube went bad.
Well I now I know what to ask Santa for. "I want tone for Xmas"

 

[tony777]

I have the 300 series mark III with 6 power tubes. From what I see on the Boogie site owners manual, the two EL34s go on the outsides instead of the middle with this model. Am I reading that right?

wooaaah!!!!!

Be careful!
quote from the MKIII manual:
NOTE: Series 300 amplifiers with Simul-Class have a different tube layout than the regular 75-watt Simuls. In the Series 300 Simuls,
the EL34/Class A sockets are the middle pair of sockets - that is, the 3rd and 4th sockets as you count across. The other sockets (1&2
and 5&6) use 6L6's.

 

[hughjass]

Riiiight. I shouldn't post at 2AM. Got that bass ackwards. Thanks for the heads up tony. Still trying to figure out how I'm going to fit this in my budget.

 

[JOEY B.]

Also I see places like the tubestore.com sell full sets of replacement tubes for a discount, but I would like to stick with Mesa tubes. Anyone know of a place I can get full sets of Mesa tubes and get the full set discount?

I have never seen any full set discount on MESA branded tubes. If you use MESA branded tubes, get a red or yellow color code for the 6L6's and a green or grey color code for the EL-34's. Your amp has about 520 volts on the plates that will shorten the lifespan of tubes that run hotter than these. If you choose to go non-MESA power tubes, get the equivalent of a #4 Groove Tubes for the 6L6 and a #5 Groove Tubes for tha EL-34's. I also see that you have a Coliseum Mark III without a "K" in the serial number. I have owned a red and a blue stripe that were the same way. The only constant with the MkIII and earlier Boogies is that there are no "absolutes". :shock:

 

[johnnyfancy]

mine's a black dot non simulclass colli. k510 serial# in the shop and i'm missing it terribly.,

 

[hughjass]

Yea! Looks like I'm getting an early Xmas present. A full set of Mesa Power and Preamp tubes. Only I got to wait on the 6L6's cuz they're coming from out of state. Prolly could have gone cheaper, but the person buying them for me doesn't like to shop online and went to Guitar Center to get the Black Friday 15% off. Beggers can't be choosers. They tried to sell her the Groove Tubes they had in stock. I thought the Mesas were overpriced, the Groove Tubes were even more! I've waited this long, I can wait a few more days. Warm creamy audio lovin is on its way. (My tubes are prolly 10 years old, 7 years in storage) They sound terrible. Do the power tubes wear evenly or are there certain ones that might be fresher. Lord knows I'm not waiting 3 days for the other tubes to plug in. I'll roll with the 4 old 6L6's till then, unless that may endanger my new EL34s? Anyone have advice on that?

 

[phyrexia]

Welcome back to taxes and tickets

 

[JOEY B.]

Do the power tubes wear evenly or are there certain ones that might be fresher.

In that particular amp, the middle two 6L6's will run much hotter, and in theory will wear out faster. Notice that I said "in theory". 8)

 

[hughjass]

Ok, I've officially damaged my hearing. Yet I smile. Still working with 4 old 6L6's, but the difference already is remarkable. I thought when I got new tubes I would spend an hour playing some smooth Gilmour leads, but I just spent an hour playing old Suicidal Tendancies and Metallica. The crunch was hard to resist. Holy crap that was loud. Can't wait for my other tubes to come in. Btw, when I got my 12AX7's, they had these rubber sheaths around them. I hope they were suppose to be left on. :roll: I had to take the one off that went into preamp slot one because it wouldn't fit under the metal sheath. I hadn't seen that before.
I acutally thought back, and I've had this amp since it was new in '89. This might be only the second set of tubes I replaced and the first since the mid '90's, coincidently about the time I focused more of my energy into destroying my brain .
So what is the major difference between Colli's with KXXX serials and mine which has a 24XXX? What did the K signify?

 

[tony777]

I don't think the rubber sheet is supposed to be on the tubes. They can get hot and melt, to be honest, I have never seen a rubber sheet on tubes, maybe I misunderstand what you try to say here, but if the rubber is kind of loose I would take it off.
Pictures can say more than thousand words.

 

[dodger916]

I don't think the rubber sheet is supposed to be on the tubes. They can get hot and melt, to be honest, I have never seen a rubber sheet on tubes, maybe I misunderstand what you try to say here, but if the rubber is kind of loose I would take it off.
Pictures can say more than thousand words.

Rubber sheathing on preamp tubes serves to reduce microphonics. Some use shrink tubing, which will not be damaged by the small amount of heat generated by preamp tubes.

However, power tubes should NOT have sheathing.

 

[hughjass]

Yeah, there is no sheath on the power tubes, only on the preamps. Heres a pic. http://trdpartsonline.com/index.php?main_page=popup_image&pID=22&zenid=7d6115a126db9c5bece4a9248f02bf08. Hope that works.

 

[lesterpaul]

Mesa typically puts these rubber sheaths on all their "specially" spec'd 12ax7's which they call/ label SPax7.
And as Frank says:

Rubber sheathing on preamp tubes serves to reduce microphonics.

As for any difference in a "K" serial numbered Coli versus a "normal" serial numbered Coli. There is none.

...unless its a SPECIAL K, like this one :lol: !thanks again,George...

 

[tony777]

Rubber sheathing on preamp tubes serves to reduce microphonics. Some use shrink tubing, which will not be damaged by the small amount of heat generated by preamp tubes.

However, power tubes should NOT have sheathing.

Haven't seen that one before, I stand corrected!!!

 

[hughjass]

Thats a purdy head there leserpaul. My colli is very clean but all black. Yours is art. Very nice to look at.

 

[hughjass]

I'm on it. Now I just need to scare up another ex-girlfriend who wants to buy me a guitar related X-mas present. I think the tubes are all I get this year. Are there any other color options?