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Re: The Mark IV thread....!!

Posted: Fri Aug 24, 2012 9:58 am
by Monsta-Tone
He has a Revision A. His Reverb circuit is quite a bit different from the Revision B.
On the A, V4 is a 12AT7. This is a lower gain, but higher current tube. I have seen several vintage Fender amps that have blown Reverb transformers because someone used a 12AX7 tube instead of a 12AT7.

I would say that it is worth it to install a new or good AT7 and see if the Reverb comes back. I have a copy of the Mark IVA manual if anyone needs it too. Can't remember who sent it to me, but I would be happy to email it to anyone that needs it.

Re: The Mark IV thread....!!

Posted: Wed Dec 12, 2012 4:37 pm
by HBob
Monsta-Tone wrote:He has a Revision A. His Reverb circuit is quite a bit different from the Revision B.
On the A, V4 is a 12AT7. This is a lower gain, but higher current tube. I have seen several vintage Fender amps that have blown Reverb transformers because someone used a 12AX7 tube instead of a 12AT7.

I would say that it is worth it to install a new or good AT7 and see if the Reverb comes back. I have a copy of the Mark IVA manual if anyone needs it too. Can't remember who sent it to me, but I would be happy to email it to anyone that needs it.

I have the old one done on a typewriter and Mesa Boogie stationery! Is that the one you have?

Re: The Mark IV thread....!!

Posted: Wed Dec 12, 2012 7:08 pm
by Monsta-Tone
That's the one. I think someone here scanned it and emailed it to me years ago.

Re: The Mark IV thread....!!

Posted: Thu Dec 13, 2012 11:02 am
by HBob
I got my amp in '92 and thought at the time it was very "mom and pop". Very cool.

Re: The Mark IV thread....!!

Posted: Sat Aug 03, 2013 5:40 pm
by cradlefish
Monsta-Tone wrote:He has a Revision A. His Reverb circuit is quite a bit different from the Revision B.
On the A, V4 is a 12AT7. This is a lower gain, but higher current tube. I have seen several vintage Fender amps that have blown Reverb transformers because someone used a 12AX7 tube instead of a 12AT7.

I would say that it is worth it to install a new or good AT7 and see if the Reverb comes back. I have a copy of the Mark IVA manual if anyone needs it too. Can't remember who sent it to me, but I would be happy to email it to anyone that needs it.

I don't believe using a 12ax7 is going to hurt the amp in any way. I don't know the reason for using the 12at7 over the 12ax7. I have never had a problem with any of my amps that I've owned using a 12ax7, but i'm sure there's a reason why mesa chose to use that type of tube for the reverb.

Re: The Mark IV thread....!!

Posted: Sat Aug 03, 2013 6:34 pm
by Monsta-Tone
The AT7 is higher current, less gain.
The AX7 may result in not enough reverb.
I've repaired a lot of vintage Fender amps where someone put an AX7 in the reverb driver slot. It blows the reverb transformer most of the time......

Re: The Mark IV thread....!!

Posted: Sat Aug 03, 2013 10:46 pm
by cradlefish
Monsta-Tone wrote:The AT7 is higher current, less gain.
The AX7 may result in not enough reverb.
I've repaired a lot of vintage Fender amps where someone put an AX7 in the reverb driver slot. It blows the reverb transformer most of the time......
thanks for shedding some light on the differences. I'll test out a at7 and check out difference.

Re: The Mark IV thread....!!

Posted: Sun Sep 01, 2013 9:16 pm
by Markedman
CudBucket wrote:
fdesalvo wrote:I just don't get how ppl can honestly say their MKIV can't get super tight, saturated, or lacks low end
+1

If I had a Mark IV with any of those symptoms I'd do the following:

1) Preamp tube swamp and if that didn't work,
2) Poweramp tube swap and if that didn't work,
3) package it up and send it to Petaluma for a checkup.
That about sums it up, but I'll add that your guitar and pick-up choice will make a huge difference. Today our bass player couldn't make it to practice and I noticed the low end of the amp was super tight when I used the bridge pick-up compared to the neck pick-up. I never really noticed that there was that much more tightness because the bass guitar picked up the slack. I did make some changes in EQ and gain structure as the practice went on and now I wonder how it will sound when we get together this week and if I'll resort back to the earlier settings.

Re: The Mark IV thread....!!

Posted: Sun Oct 20, 2013 2:18 am
by mazzith
Today my other guitarist found a Mark IV A compact head on craiglist (without pedal) for $800.
I have the Mk IV B head and we played both heads through the same cabinet using the same guitar with exact same settings. The tone differences was very minimum.
Later on we are going to do some side by side recording comparisons.


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Re: The Mark IV thread....!!

Posted: Sat Oct 26, 2013 9:23 pm
by darkalone
Hi everyone. Got an issue with my Mark IV and I was hoping someone could steer me in the right direction. I created a thread outside of this one. Basically, my volume dropped considerably across the board, gain channel also sounds like it's crapping out, and now the signal seems sort of intermittent.

Thread: http://forum.grailtone.com/viewtopic.php?f=3&t=65570

I'm guessing it's in need of a re-tube. But that leads to all sorts of other questions, mainly, what kind. :?

Anyway, any help is appreciated. Thanks guys.

Re: The Mark IV thread....!!

Posted: Mon Dec 02, 2013 9:24 am
by Markedman
I put new tubes in my Mark IV on Saturday. Someone gave me a pair of Mesa STR 420's so I tried them in the outer sockets at first along with the GT 6L6's in the middle. That sounded awesome, nice and tight. Next I tried the =C= el34's in the outer sockets and that had the typical "jangly" sound associated with Marshall amps. Next I put the 420's in the middle, 34's in the outer sockets and have been playing it that way trying different settings. I'm using the amp in simul-class, triode, full power, and I think that is what I'll use. My band is on holiday break, and I love my other Mark amps when I play with the band, so I never really use the Mark IV live unless it is at an "open mic," home practice or playing at a friend's house. I'd say the combination of 6L6 & el34's is best all around, but a quad of 6L6's would be my choice for metal only, the amp sounds less spongey and much tighter with 6L6's. I have different pre-amp tubes on the way.

Re: The Mark IV thread....!!

Posted: Sun Jan 05, 2014 9:59 pm
by boogietone
I sent you a Mark IV manual or something like that last year, I think.
Monsta-Tone wrote:That's the one. I think someone here scanned it and emailed it to me years ago.

Re: The Mark IV thread....!!

Posted: Wed Oct 08, 2014 7:07 pm
by andrewraharjo
Hi everyone, I just got my used wide body mesa boogie mark IVB 2 days ago. It's a beautiful combo and I'm thinking of make as head cab which I'm looking for head shell now.

I tried to call Mesa the other day and they quoted me with $356. Does anybody here have any idea for cheaper solution ? I heard there is member here "gts" who can make it happen for less than Mesa quoted me. Does he still make head shell these days ?

Re: The Mark IV thread....!!

Posted: Tue Nov 18, 2014 6:20 am
by philip
hey there,
new to the forum and I just picked up a Mark IV last week.
amazing amp! so far I was able to play it only at bedroom levels,
but even pretty quiet it does sound incredible.

apparently it's a pretty early on, too.

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does anyone know what the jack in the last image is for?

Re: The Mark IV thread....!!

Posted: Tue Nov 18, 2014 8:19 am
by tonejam
No, but congratulations on the amp!