How many diffenent Versions of the Mk2 b?

[needtoknowbassist]

When is was ordering tubes from Euro Tube I notice they didn't offer mk2b packages like they do for the Mk1, 3 & 4. When I emailed them I was told that there was over 20 versions/configuration of the mr2b.

Is that true, 20?

How does that compair to other Mark Series?

 

[Dutchman]

I guess if you add them up there are many versions.

http://homepage.mac.com/mesaboogie/MarkIIB.html

Mark IIB 1X12: 5575-11000 = 5426 Mark IIB
Mark IIB 1X15: B550-1100 = 550 Mark IIB
Mark IIB Series 300: K001 to K336 = 336 Series 300 Mark IIB
August 1980 to May 1983 = 5212 Mark IIB's

Call Mesa with the serial number and they will tell you what it needs.

 

[igfraso]

I recall that, when you ask Mesa about II-B mods, they ask for the serial number. If it is above 7,000 or 8,000 (I cannot remember the cutoff) the EQ addition is more expensive than if the S/N is lower than that.

Does it mean that those are different versions?

 

[BPski]

I am a tech and have worked on more than a few IIB's (mostly the ones I have owned). There is a serial number near the mid 8000's I believe where the circuit changed. There were little tweaks along the way through the whole IIB series but there was definitely a change in the 8000 area. Mike B told me a more precise number but I do not remember it. I never opened up a Coliseum model so I cannot say. The 60/100w 1x15 version is the same circuit as the head and 1x12. I do not think there are 20 versions circuit wise. I can tell you that the pre circuit change IIB's use a different tube configuration than the post change. Some 12At7's instead of 12AX7's. I hope this helps. I would just tell the sales person at euro tubes the ones you need individually. Check the chassis for the markings. Have fun!!

 

[needtoknowbassist]

thanks

Just go my tubes from Euro Tube, and what a differnce. I haven't had a chance to really crank it up yet (7 month old daughter, and a very dirty look from the 28 yr old wife when I tried). I did get a bit a noise from on of the channels, I think it is just dirty tube sockets. Looks like the preamp tubes have never been changed. I'm going to stop at Radio Shack and by some contact cleaner.

I went for the early breakup 6L6, and a balanced 12ax7 for the PI.

I still need to do the caps, but the a much tighter sound than before.

Thanks

 

[BPski]

Yeah, clean the sockets. Also I notice some noise from brand new tubes until the "burn in". There are gasses left over from manufacturing and after using them for a while they quiet down. I would guess around 48 hours or so, sometimes less. Try the socket cleaning first, then play that amp!!