Boogie MKIIB question

[Echo21]

I have somewhat of an anomaly of an amp, its a MKIIb with a serial number in the early 10,000 range. The knobs are not the concave silver, but the solid black like the IIC's, it has a IIB front panel, but it passes the loop test. Tonally it has mondo gain that is very smooth, not harsh like some of the III's that I've played. I don't even need to get the gain past 5 and I'm getting 80's Metallica easily. The clean is also very smooth and glassy, and there's no popping in the footswitch. Can any boogie experts out there explain this amp?

 

[bartchamdoh]

Hi the transitional models just before mesa changed over to the Mark 2c used the all black top hat style knobs that you describe and that they used on the rest of the mark2/3 series.I myself have a fully loaded super sixty short head(converted from a combo)that is in the same serial number range that you describe which has these knobs,my research leads me to believe that they probably made 500/600 of these cross over models!Sometimes if an amp was sent to the mesa factory the factory installed these newer top hat style knobs on the older amps.Interestingly the mesa 1984 brochure uses some of these transition models to promote the at the time new mark 2c in the photo shoots!!!(i know this because i have the said brochure lol)It may be that your amp has been modded as my mark 2b still has the foot switch pop,there is an fx loop mod that mesa did at the time which also improves the lead channel.Imo the mark 2 had the best clean channel of the mark series very warm,round and punchy which sits well in the mix live and for recording.Also sounds amazing with pedals and this is my main amp live sounds amazing thru any of my mesa 2x12s with a pedal board up front....hope that helps.

 

[Echo21]

Thanks for the comments. Its a 60 watter, no EQ or reverb. Here's a link to the pics of the amp and guts. Let me know what you think.

http://s582.photobucket.com/albums/ss270/Shooter1371/

 

[bartchamdoh]

I,ve looked at the pictures of your amp and it,s hard to tell if there,s the famous cross above the power chord which means you have the holy grail of tone lol,however your slave out has the concave silver style knob of the earlier amps and the presence knob on the back(from the picture mind you)looks like a replacement.Imo your amp looks like it,s been sent back to the factory for some work and upgraded but that,s just an educated guess!....you could always phone mesa with the model and serial number to see if they have any info.

 

[Echo21]

There's no "+" above the power cord. I talked to mesa and they said this amp has never been returned to the factory for mods. However they also said that it could have been modded during original production at the factory. Aside from the tone, the biggest puzzle to me is the loop test, which it definately has the characteristics of the C+. If someone can tell what this is by the amp guts pics, I'd sure appreicate it.

 

[acorkos]

the circuit boards look like stock IIB...only one relay for channel switching, no multiple vactrols like in a IIC, IIC+ or III

 

[kakev]

I have fully loaded MkIIb head with serial #10 8XX and I'm fairly sure it's all original. Has those black knobs. It passes the loop test suggesting it's C+, but I don't think it is. Dont know what to make of that. Great amp anyway, from beautiful cleans to highgain lead -tone. No prob. Doesn't have as much gain as my Studio preamp, but enough. Studio pre has got way too much gain on the lead channel anyway..

 

[Echo21]

I've been doing some research and back in the day Randall and Mike were modding the effects loop as some guys have mentioned here. The mod affected the lead channel that comes close to the IIC+ sound, this could be the reason for passing the loop test. At any rate, whatever it is, I like it. Great cleans and killer lead sounds.

 

[chipaudette]

Hi All,

My read of the Mark IIB schematic says that they should all pass the "loop test".

And, to be clear, my understanding of the loop test is:

1) Plug guitar into "Effect Return"
2) Switch to Lead channel
3) Play a chord
4) Twiddle the "Lead Drive" knob

If the "Lead Drive" knob has an effect, it is a IIC. If the "Lead Drive" has no effect, it is a IIC+.

The loop test is what distinguishes a IIC+ from a IIC because it was the IIC that was weird. Its effect loop was located way earlier in the overall amp circuit than the in the IIC+. The location of the loop in the IIC+ circuit is much more similar to the IIB and III. So, the loop test should only "fail" for the IIC because it had a weird design, not because the IIC+ had a unique design.

So, IMHO, I would not take the "loop test" as a indicator that your IIB was upgraded to a IIC+. All it says is that your amp is not a IIC.

Chip