Mark IIb serial numbers

[James]

Hey James you have the same lettering on your amp as mine. So does the b of 83 represent feb of 1983? Mine says D of 83 with same initials . Mine is a 107**

That's interesting. I always thought it was an 8, suggesting August 1983. But that doesn't match up with the info above. It has a lower serial than 10543 (January), but still a 1983 build - so I'm guessing it's one of the very first amps from that year.

I would guess your amp is from the first quarter of 1983 anyway. Probably one of the last IIBs made - does it have the black knobs like the IIC and later, or earlier ones (Fender style) with the silver insert?

The top edge of the chassis has the spec. The SR on yours means sixty watt/reverb. Mine is HRX - hundred watt/reverb/export PT.

But I'm not sure about what's written below.

Also, anyone know if those are Mike's initials? I've seen a number of amps that look like "MD" but I assume it was just Mike in a hurry

 

[Lyon76]

my amp has the black knobs, I asked mike if that was his initials on the amp when he serviced and loop modded mine last year. I believe he said no. I would have to check my emails. But if the d represents April , I guess it would make sense since that was around the end of the run of 2b’s. Yours is the only other one I’ve seen with a letter next to year. I always see the specific date/month/year on prior chassis.

 

[Lyon76]

By the way Is your gain boost an actual pull deep?

 

[Lyon76]

I went back through my emails with mike from last year and he said he had a 910* on the bench and it had the rp9c board in it.

 

[James]

my amp has the black knobs, I asked mike if that was his initials on the amp when he serviced and loop modded mine last year. I believe he said no. I would have to check my emails. But if the d represents April , I guess it would make sense since that was around the end of the run of 2b’s. Yours is the only other one I’ve seen with a letter next to year. I always see the specific date/month/year on prior chassis.

That's interesting if true. I'll have to check if my IIC also has a day and month, as that's also a 1983 build.

The IIB has the gain boost. From what I understand, the very last IICs were the ones that sometimes didn't match. Mine has the pull deep on the face plate, but would have had the gain boost function as stock

 

[Lyon76]

I’m not talking about the wording but actual pull deep circuit. I guess it started in the late IIb

 

[erickompositör72]

I’m not talking about the wording but actual pull deep circuit. I guess it started in the late IIb

I had one with a 9A preamp board that had the "pull deep" circuit (the way Mike B. describes the difference is that if you put T-M-B all on "0", and then pull "gain boost," the older circuit will suddenly jump from no sound to lots of sound. I believe it's the same idea with the dumble style preamp boost.)

The serial on that IIb was 893x

 

[user 41014]

Here's a headscratcher for this thread. Serial # 540X w/ Export Transformer dated 6/24/80.

Preamp Board # RP 8C. Mike B. has been in this one (loop mod & preamp tweaks).

Looking at Mesa’s serial # range, it looks like this may be a very late IIA or early IIB?
View attachment 1263View attachment 1264

headscratcher indeed- I'd raise one eyebrow if I could.

A member on here has 539x also with export tranny dated 6/19/80 which falls in line with your serial and date but with RP 8B.

5660 just sold tho and also had RP 8B dated 8/21/80. I can only guess the limited amount of exports has something to do with a one off date wise but it is curious.

Yours being 540x and you say it is 6/24/80 makes sense except the RP 8C. But it is a small sample size and those are the only 3 boards I've seen on serials 5400-6000.
Anyone got more in the lower end of that range?

 

[Wyzard]

Ever late to the party.......

I've got a MkIIA HGX (written XPHG on the chassis side) s/n 524*, dated 5/28/80, and with the SP6A board.

It looks like it's never had the Fetron switch installed, despite having the TR1009/12AX7 switching info panel stuck on the inside of the combo shell.

 

[Wozza]

Just to contribute… I have a Mk11A dated 08/21/1 serial number 462x with the SP6A board. Marked XPSSG?

 

[Appleridge]

Here’s another!

Mark IIb
sn103xx
RP-9C
Black knobs

 

[pastorofmuppets]

and another IIB

12/29/81
sn838x
RP9B
HRG
Silver knobs

 

[Brandon Breeze]

I had Serial #8484, 12-81, HRGX, X-101 Transformer, RP9C Preamp board. It was sent to Mike B in 2023 for the Loop Mod and was fantastic. Originally an Imbuya 1x12 Combo, now in a white SOB Headshell (when sold)