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PostPosted: Wed Dec 10, 2008 1:19 pm 
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Bottle Rocket

Joined: Fri Nov 14, 2008 9:27 am
Posts: 5
Very early (November 1978) mark 2a with the 60/100 option.

Couple questions:

when in 60 watt, which 2 power tubes are "on"?


Also...On the bottom of the chassis in between tube sockets there is a pre amp out and power amp in jacks (again, on the bottom, not on the back), however, these are not labeled. So if I am looking at the bottom of the chassis with the back of the chassis closest to me, which is th pre amp tap and which is the power amp?

Same with the Reverb RCAs no "Send" and "return" on them. Looking at the bottom of the chassis with the back closest to me, is the closer rca jack send or return?


Thanks!


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PostPosted: Wed Dec 10, 2008 1:34 pm 
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Bottle Rocket

Joined: Fri Nov 14, 2008 9:27 am
Posts: 5
On a similiar subject, they (mesaboogie.com) have manuals for every "Mark" version except the 2a, which leads to some confusion should I use mark 1 manuals? mark 2b manuals?


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PostPosted: Sat Jul 09, 2011 9:45 pm 
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Mark IV

Joined: Fri Jun 30, 2006 7:00 pm
Posts: 883
Pigs_Boogie wrote:
On a similiar subject, they (mesaboogie.com) have manuals for every "Mark" version except the 2a, which leads to some confusion should I use mark 1 manuals? mark 2b manuals?


It's closer to a Mark I than a IIB.

Manual original settting (nothing pulled):

- Vol1: 4
- Treb: 9
- Bass: 3
- Mid: 3
- Mast1: 2
- LD: 7
- LM: 1
- Presence: 3

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PostPosted: Thu Jul 14, 2011 12:52 am 
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Mark III

Joined: Thu Aug 24, 2006 12:44 pm
Posts: 250
Pigs_Boogie wrote:
Very early (November 1978) mark 2a with the 60/100 option.

Couple questions:

when in 60 watt, which 2 power tubes are "on"?


Also...On the bottom of the chassis in between tube sockets there is a pre amp out and power amp in jacks (again, on the bottom, not on the back), however, these are not labeled. So if I am looking at the bottom of the chassis with the back of the chassis closest to me, which is th pre amp tap and which is the power amp?

Same with the Reverb RCAs no "Send" and "return" on them. Looking at the bottom of the chassis with the back closest to me, is the closer rca jack send or return?


Thanks!


I can't answer most of your questions directly but below is a way to figure out what is what.

1. The tubes that are on when in 60 watt mode are the outside tubes.

2. Refer to the schematic at the link below for the pre-amp-out/power-amp-in question. I am assuming the schematic labeled Mark II is the same as the Mark IIA.

http://www.webphix.com/schematic%20heav ... oogie.html

Looking at the schematic the pre-amp-out/power-amp-in are labeled as the same jack. There is another jack labeled as Effects Send. You should be able to identify the Effects Send by plugging in a cord. With a cord plugged in the shorting connection will open and disable the output, i.e. no amplification. A cord into the pre-amp-out/power-amp-in will not affect output as there is not a shorting connection that opens with a cord in place.

3. The only way I can think of to id the two reverb RCA connectors without going inside the amp is as follows. You will need an ohm meter. With the amp OFF and unplugged measure the resistance of one of the RCA jacks. It will either be a real low resistance (this is the one connected to the transformer or reverb input) or about 220K (which is the reverb output). Sometimes the ground side of the RCA connectors are not connected so use the chassis for the ground rather than the RCA jack. If you are inside the amp then just trace the circuit out.

Clearly to do the above you need to be able to read a schematic and have access to an ohm meter. Hope this helps and let me know if the above explanation is not clear or you need clarification.


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PostPosted: Thu Jul 14, 2011 11:36 am 
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Bottle Rocket

Joined: Fri May 13, 2011 10:06 am
Posts: 7
My IIa combo is from late 79...only jacks on bottom are(from back) effects send(L) and footswitch (R). Reverb send (white wire)is in front of return(grey wire). White to L side....grey to R side of reverb tank, RCA jacks faceing towards speaker.
Replaced my broken tank with a MOD.....sounds fantastic.

Here is a IIa manual, includes trouble shooting section and schematic. Click on green box(pdf). Lots of good info......

http://www.commentcamarche.net/notices/ ... iia-14140/


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PostPosted: Thu Jul 14, 2011 9:37 pm 
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Mark IV

Joined: Fri Jun 30, 2006 7:00 pm
Posts: 883
A little info coming from the MarkIIA manual, just in case you all are interested...

For amps prior to serial nos. 3500 or 360 for 1-15 models, if the amp is dead or extremely weak, test the Effects Send jack (located beneath the chassis on the left) by plugging a guitar cord into it and running the other end into the PWR AMP IN jack on the rear panel. Occasionally the internal contacts of the Effect Send become faulty.

Amps past #3501 and #361 have a 220K resistor wired across Effects Send jack to prevent signal drop in the event of a contact failure. Signal strength of Effects Loop may overload effects device and cause distorsion at high settings.

Another topic... I thought the Mark IIA didn't have an effects loop and that there was only a patch point between pre-amp and power amp (PRE AMP OUT/PWR AMP IN).

However, according to the metal plate that is glued to the cabinet of the amp, it states:
- Effects send: jack on bottom left of the chassis
- Effects return: Pwr Amp In jack on rear panel

Can someone explain this apparent contradiction?

Thanks and best regards

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PostPosted: Fri Jul 15, 2011 3:08 pm 
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Single Recto

Joined: Thu Jul 21, 2005 2:56 pm
Posts: 1584
Location: Pacific Coast
I don't mean to be Microsoft Tech Support Department giving you information that's totally useless but

my Mark IIB has two 1/4" input jacks on the bottom of the chassis.

One was stereo (sleeve, tip, ground) for my gain boast and EQ footswitches.
The other jack was a power-in say you have a preamp out from another amp, you plug into this jack so you could use the power stage of the Mark IIB. You could also use this input with a passive volume control pedal like Ernie Ball's. Yes, just one cable is required.

my Mark IIB did have an send and return effect loop jacks at the back of the chassis. Not sure what's the configuration of a Mark IIA, I though it was similar to Mark IIB.


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PostPosted: Sat Mar 10, 2012 1:32 pm 
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Mark III
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Joined: Wed Feb 10, 2010 12:07 pm
Posts: 329
Location: Marysville, California, USA
igfraso wrote:
... Another topic... I thought the Mark IIA didn't have an effects loop and that there was only a patch point between pre-amp and power amp (PRE AMP OUT/PWR AMP IN).

However, according to the metal plate that is glued to the cabinet of the amp, it states:
- Effects send: jack on bottom left of the chassis
- Effects return: Pwr Amp In jack on rear panel

Can someone explain this apparent contradiction? ...


My Acoustic 165 is a direct rip-off of the early Mark II even down to the FET switch and I discovered, by comparing my Mesa amps to this weird thing, I could use the PRE AMP OUT/PWR AMP IN as my effects loop. I can only speculate that early amps with this feature would actually address this for sending the pre-amp out to another power amp or another pre-amp going into the power amp circuit of same.

Dennis

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Mark III no mark w Randy's initials & some IIc+ parts
50 Caliber (6BQ5) 4xEL84
Heartbreaker
Fender 75
Acoustic 165

1970 LPGT
1981 The Strat
1983 GZ-300
1983 (Elite Neck)/2001 FrankenStrat
1990 Firebird
more guitars, so little characters


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PostPosted: Sat Mar 10, 2012 6:42 pm 
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Mark I

Joined: Sat Feb 04, 2012 3:00 pm
Posts: 45
igfraso wrote:

Another topic... I thought the Mark IIA didn't have an effects loop and that there was only a patch point between pre-amp and power amp (PRE AMP OUT/PWR AMP IN).

However, according to the metal plate that is glued to the cabinet of the amp, it states:
- Effects send: jack on bottom left of the chassis
- Effects return: Pwr Amp In jack on rear panel

Can someone explain this apparent contradiction?

Thanks and best regards


Hi, my Mark IIA is dated 12/78. To answer your question, yes the patch points will work as an effects loop but you need certain equipment to do so. The problem is that the preamp out signal is very strong and will overload your effects in most cases. Some higher end effects devices may work, as they are able to deal with the hot output of the preamp out jack. Another solution that i find to be easier is to use an effects loop buffer setup. Basically it will take the hot output of the preamp out jack and reduce it to a usable level for your effects, and then it will boost the signal back up to drive your power amp section. This is what i decided to do, and i started a thread about it here http://forum.grailtone.com/viewtopic.php?f=27&t=58524


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PostPosted: Wed Mar 21, 2012 9:48 am 
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Mark II
User avatar

Joined: Tue Oct 11, 2011 4:36 am
Posts: 123
Location: Austria
igfraso wrote:
It's closer to a Mark I than a IIB.


Sorry igfraso, thats wrong :wink: . If you look at the schematics (http://tubefreak.com/mk1.gif http://tubefreak.com/mk2.gif ), Mk I and Mk II are quite different, Mk IIA and IIB are very close, in Mk IIC they changed reverb and send/return and the lead channel. They built an extra send and return on the Mk IIB right after the cathode follower of V2B.
To your original questions:
on 60 Watts the two inner 6L6 are shut off
power amp in/out is one jack and you can use it for either plug in another preamp or send the preamp signal to another amp. its not useful for effect send/return cause its much too stong.
reverb in/out: try it! if you plug in right the reverb works, if wrong it doesn't.

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Mesa Boogie MkIIB
Mesa Boogie Studio 22+
BF Deluxe Reverb, SF Vibrolux, SF Bronco, Fender BJ
Kitty Hawk Standard, Kitty Hawk Junior
73' Marshall JMP Super Lead
Marshall 6100 Anniversary
Marshall 2555 Silver Jubilee
Hiwatt Custom 50
Acoustic G60T


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PostPosted: Wed Mar 21, 2012 10:34 pm 
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Mark IV

Joined: Fri Jun 30, 2006 7:00 pm
Posts: 883
TiPiMods,

I know what you are saying. Mesa says that in the Mark I the first two preamp stages occurs before the tone controls. In the various later Mark II and III models, there is only one gain stage before the tone controls.
From this point of view, the architecture of the Mark IIA is definitely closer to the IIB.

However, I understood the original poster was asking about settings since he didn't have the IIA manual. I just meant to say that the Mark I and the IIA are the only Boogies where you may want to set the Volume 1 to 4.
For all the rest of the Boogies, the suggested setting for Volume 1 is 7.

Regards

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Daniel


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PostPosted: Thu Mar 22, 2012 11:54 am 
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Mark II
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Posts: 123
Location: Austria
I understand...didn't know that a IIA is that different in setting, since the schematic is very close to a IIB.

btw: I just started a new thread: viewtopic.php?f=27&t=59008 where I suggest that all the MkII lovers in this forum post their favourit MkII settings. Maybe we get some interesting suggestions and inspiring sounds.

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Mesa Boogie MkIIB
Mesa Boogie Studio 22+
BF Deluxe Reverb, SF Vibrolux, SF Bronco, Fender BJ
Kitty Hawk Standard, Kitty Hawk Junior
73' Marshall JMP Super Lead
Marshall 6100 Anniversary
Marshall 2555 Silver Jubilee
Hiwatt Custom 50
Acoustic G60T


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PostPosted: Thu Mar 22, 2012 4:17 pm 
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Mark IV

Joined: Fri Jun 30, 2006 7:00 pm
Posts: 883
TiPiMods,
this is a copy of a posting I placed here in June 2011.

QUOTE
There is little information in this forum about the MarkIIA so let's invite every MkIIA lover to discuss your preferred settings.

1) Good basic setting I (Manual quick start)
Vol1: 4
Treb: 9
Bass: 3
Mid: 3
Mast1: 2
LD: 7
LM: 1
Pres: 7
Rev: 4
EQ: out

2) Good basic setting II (Manual alternative)
Vol1: 6
Treb: 7
Bass: 4
Mid: 0
Mast1: 2
LD: 8
LM: 1
Pres: 7
Rev: 4
EQ: out

3) Jerry Garcia
Vol1: 8.5
Treb: 6.5
Bass: 2
Mid: 8
Mast1: 2
LD: 7
LM: 1
Pres: 3
Rev:
EQ:

4) SRV
Vol1: 7 pulled
Treb: 7 pulled
Bass: 4
Mid: 5
Mast1: 2
LD: 9
LM: 1
Pres: 8
Rev:
EQ:

Hope it helps.
Daniel
UNQUOTE

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PostPosted: Thu Mar 22, 2012 4:25 pm 
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Mark IV

Joined: Fri Jun 30, 2006 7:00 pm
Posts: 883
Also, according to Mike Bendinelli, the MkIIA has a very unique sound for the Mark series. He says it is kind of a hot-rod Tweed Bassman.

It is a dark amp that goes very well with 335 guitars. In order to brighten up the amp, you can go with the EVM, an Altec or an JBL K120 (alnico V speaker).

Regarding the suggested settings here above, keep in mind that if you use single coils, you may want to reduce a little bit the presence and the treble.

Regards

_________________
Daniel


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PostPosted: Thu Mar 22, 2012 4:58 pm 
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Mark I

Joined: Sat Feb 04, 2012 3:00 pm
Posts: 45
igfraso wrote:
It is a dark amp that goes very well with 335 guitars. In order to brighten up the amp, you can go with the EVM, an Altec or an JBL K120 (alnico V speaker).



Interesting. My IIa is anything but dark sounding. In fact, it is a bright monster so to speak. I would be interested to know what kind of tubes affect the IIa to sound dark or bright. I am running some very old and powerful Sylvanias in the power section, maybe thats whats giving me the bright sound?


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