Dating my Mark IV Combo

[chino007]

Serial # on my Mark IV combo saids IV 0205 can anyone help me identify possible year and if it's an A or B???

Just picked this amp up about a month ago and I think I finally got it tweaked in.

 

[Mongo1]

Yours sounds like a MKIVa.

MkIV A 1991-1994
serial 0000-around the 6XXX's
-two mono FX loop's (normal And Switchable) The four plugs form a box shape.
-12at7 in V4 ( the reverb tube slot)
-No reverb foot switch on the back.
-older style tolex and LED's.
-Smaller power transformer than the B.

Check out this thread: http://forum.grailtone.com/viewtopic.php?f=27&t=5987&start=660

 

[igfraso]

It could also be a 1990.
Check the date of manufacturing inside the chassis.

 

[chino007]

Thanks, there's actually a manufacturing date inside the chassis??

 

[topcat0399]

Sometimes the guy that works on it writes it in there. Mine has the builders markings all over inside including dates.

I've seen some gut shots where there wasn't much writing also.

Don't be afraid to pull your amp apart; its VERY simple and quick. For me laying the combo on its side, pull the 4 screws, unplug the fan cord, and slider her out the back works best. I usually pull the power tubes but I'm pretty sure it can be done easily with all tubes left in place.

If there is a Jack on the bottom that is unmarked (reverb switch jack) - you might have a wierd one like me. Some kinda 'tweener'.


good luck man

 

[chino007]

I already seen a weird jack all the way to left next to the serial # with no markings on it underneath

 

[lerxst88]

I should also mention the values of the resistors around the power tubes are different from versions A and B.

Checked my early B against a schematic and the values were definately different. The schematic was from 1992 so that would be an A

 

[chino007]

Yea I placed a call to Boogie and had to leave a message with Serial # for info as from all the reading I've been doing on this Forum it appears apparent that it would be benificial to know exactly how early or late my Mark IV came out in order to make an informed decision on which tubes to use when I retube the whole thing as the person I purchased it from couldn't tell me the age of the tubes, currently can see that it has STR 440's in it now, couldn't see the preamp tubes clearly except for the 12at7 I can see. Any Suggestions??

 

[igfraso]

Those are not the original power tubes. The Mark IV-A came equipped with STR 420, as far as I know.

You will find the manufacturing date written on the bottom side of the chassis.

 

[MrMarkIII]

Yea I placed a call to Boogie and had to leave a message with Serial # for info as from all the reading I've been doing on this Forum it appears apparent that it would be benificial to know exactly how early or late my Mark IV came out in order to make an informed decision on which tubes to use when I retube the whole thing as the person I purchased it from couldn't tell me the age of the tubes, currently can see that it has STR 440's in it now, couldn't see the preamp tubes clearly except for the 12at7 I can see. Any Suggestions??

You've got an early "A". The 12AT7 is the reverb tube. The "B" model went to the 12AX7. Not a huge deal. The STR-440 is the latest stock Mesa tube, but any Mesa tubes will work. You can put EL34s in the outer sockets, and 6V6s in all four if you use Simul-Class/Tweed Power *only*.
Any tube seller can sell you tubes that will work in a Mesa if you tell them what model you have, so you're not necessarily limited to the Mesa "brand".
Don't buy new pre-amp tubes just because "they haven't been changed in a while". They last many times longer than the power tubes. You can swap 'em out to experiment with changes in tone. It's a fun hobby.

 

[chino007]

Thanks for the advise, I actually went ahead and replaced the preamp tubes except for the Reverb tube as there was crackling and popping which did go away, also have some old matched Quad 6v6's that I know only had about 15 hours on them total as I used to use them in a Heartbreaker I used to own, doesn't sound bad, am going to convert to a head though, I actually like the sound of my Celestion Black shadow in my 1x12 cab over the EV Black shadow in the combo, Also noticed when I pulled out the STR 440's that three were labeled green and only one was labeled red, that sucked, I'm going to try 2 of the green in the middle with 2 JJ el34's I have on the outside to see how that sounds. Looked closer and found the Manufacturing date to be Sep. of 1990, so I guess this one is a real early model A with weird unmarked jack underneath. The Customer rep at Boogie told me it was 205th built by the serial #

 

[Mongo1]

The jack underneath should be the remote EQ control for connecting to a Simul-Sattelite amp. It allows the MKIV to be used as a stereo setup and will allow both the MKIV EQ & the SS EQ to be switched together from the MKIV footswitch.

Here's a pic of the corresponding SS jack.
http://forum.grailtone.com/viewtopic.php?f=27&t=44643&start=0

 

[chino007]

Thanks for the info, someone earlier in the thread suggested it was a reverb switch jack??

 

[Mongo1]

Check out this thread:
http://forum.grailtone.com/viewtopic.php?f=27&t=32180&start=0

 

[chino007]

thanks, anyone know the difference between the Celestion 90 watter in my ext cab and the EV 90 watter in the combo cab, I like the sound from the Celestion better than The EV but everyone boasts about the Ev,, Sounds thinner ,tinnier,boxier, and lees bottom end to me???

 

[topcat0399]

The jack underneath should be the remote EQ control for connecting to a Simul-Sattelite amp. It allows the MKIV to be used as a stereo setup and will allow both the MKIV EQ & the SS EQ to be switched together from the MKIV footswitch.

Here's a pic of the corresponding SS jack.
http://forum.grailtone.com/viewtopic.php?f=27&t=44643&start=0

Mine was built 3-17-91 according the the info written on the inside of my chassis. It has the Loop jacks in a square layout, and marked 12AT7 for the reverb.

OP only mentioned the one jack on the bottom; probably the jack for the Reverb Remote Switch.

On the back of the chassis there is a multi-switch for the graphic eq. Just below that might be the words:

REMOTE (with a little arrow pointing down). Its for switching the 'verb off and on.


I wouldn't be too hasty on chopping up your combo. I had mine a year before I got the knack of setting it and longer than that before I fell in LOVE with this amp.