Mark II C+ 15” Combo Service?

[throbak]

I just bought a Mark II C+ 15” Combo from an old friend that bought the amp new. The power tubes are all 6L6’s and I believe the outer two should be EL34’s. My question is can I swap these outer tubes for EL34’s without biasing the amp? Is it a problem to leave the 6L6’s in place? And given the age of the amp should I send the amp in to Mesa to have the electrolytic caps replaced? It sounds great as is and seems to have no issues.

I play in a blues band but I know these are sought after for their metal tones and I want to preserve the amp and maintain the value of it. I am far from an expert on Mesa Boogie so thanks for the advice in advance.

 

[rarebitusa]

Well, depends is it Simulclass or a 60/100?

 

[MisterMojo]

It could be an H (60/100W), which would want to see all 6L6’s. If it’s a D (SimulClass), 6L6 inner and EL34 outer. If you’re not sure what version it is, pull the chassis and check the OT. If it says SimulClass on it, you can put EL34 in outer. Regarding biasing, unless the amp has had a bias pot added, you don’t bias Mesa’s. You should either get Mesa tubes, or, if you have equipment to test and measure tubes, you can select tubes based on which model it is (D or H). For H (all 6L6) I looks for tubes that all run at 36-39mA at idle, and if D same values for 6L6, and then 25-30mA for EL34.

I would definitely consider having Mesa service it, while you can take advantage of it. They could hook you up with proper tubes for it, too, if you don’t want to tackle that.

BTW, great amp! I’ve had a number of 15” combos over the years.

 

[throbak]

I have not pulled the chassis but I suspect it is a 60/100 as it has a half power switch on the front.

 

[throbak]

If I do decide to ship to Mesa should I send the entire Combo in the original Anvil flight case that came with the amp. Or should I ship the just the chassis? If I send the entire amp they can check the fan etc...

 

[MisterMojo]

Regarding the 60w/100W switch… don’t let that suggest that it’s an H amp. They had limited long chassis faceplates in those days. I’ve had 2 C+ (still have one) D amps that had Full/ 1/2 power on the plate.

As far as what to ship them? I only send the chassis. Shipping a 15” combo is $$$. If you want, you can send the reverb tank (assuming you have one), too, as they can be problematic at this age.

 

[WAG]

Mike B is really backed up as well so be prepared for an extended break from the amp.

 

[Markooo99]

Could you post the exact dimensions of your amp? I’m thinking about building a new cab for my iib that would have a 15” instead of a 12”. I’m trying to find out the size of original cabs with the 15”.
Thanks.

 

[GJgo]

What MisterMojo says. You need to pull the chassis & see what's written on its side. There should be a chassis code in sharpie that will tell you.

Also highly agree with having Mike B. at Mesa service it while you still can. Ignore the wait & the cost, the window of opportunity will close soon.

Congratulations brother, if you paid less than 7 grand for it these days you're in a great position.

 

[throbak]

I pulled the chassis and it is a DRG Mark II C+.

I got the amp back last week from Mesa. Mike B. serviced it. He changed the electrolytic capacitors and 5 pre-amp tube resistors that were out of spec. The power cord ground was intermittent so he changed that and he also replaced a bushing in the reverb pot.

The amp sounded great before I shipped it to Mesa and it sounds even better now! The low end was a little boomy before the work was done and now the low end is full, but not boomy. It also seems easier to dial in the perfect tone now. It just feels like a broader spectrum of tones to choose from now. Less touchy to small adjustments.

It is without a doubt one of best amps I have ever played. For edge of breakup Blues tones it is extremely dynamic and responsive to pick dynamics. I know these are sought after for heavier tones but for Blues and Rock tones, the amp is amazing.

 

[MisterMojo]

Congrats on getting your amp back! I just recently received my 15” DRGX back as well. I agree… they are more than just for heavy tones. A very versatile amp with a bunch of great tones. You’ve got a unicorn there… enjoy it!

 

[rarebitusa]

It is without a doubt one of best amps I have ever played. For edge of breakup Blues tones it is extremely dynamic and responsive to pick dynamics. I know these are sought after for heavier tones but for Blues and Rock tones, the amp is amazing.

+1 8)