Mark V preamp tube layout?

[madrigal77]

Does anyone have a schematic for the Mark V that shows the preamp tube positions and functions. I'm looking for something like this (this is for a 5150):

Here is what they do, In order
from Left To right (pre-amp)
v4: Phase Inverter
v3: Effects Loop Buffer
v5: Gain Stage - Cathode Follower, Lead
v2: Gain Stage - Full Lead
v1: Gain Stage - Full Lead, Half Rythm

Thanks!!

 

[mejoshee]

user manual:
http://www.mesaboogie.com/manuals/MkV_100303.pdf

it's on pg. 66 of the pdf. cheers. 8)

 

[madrigal77]

Thanks

Basically I just need to know where the cathode follower is so I don't accidentally throw a Tung Sol or something in there. The diagram shows the gain stages, but not where the CF is. Anyone know?

 

[4406cuda]

I put in all Tung Sol 12AX7's in mine and it was a great improvement over the JJ's that were in there.

 

[madrigal77]

I put in all Tung Sol 12AX7's in mine and it was a great improvement over the JJ's that were in there.

And they are holding up fine? Because apparently Tung Sols blow pretty quick in most CF positions.

 

[eudaimonia02912]

I seem to remember someone contact MB about this and they said that the Mark V doesn't have cathode follower positions.

 

[MrMarkIII]

I think I found this on Mesa's website. Don't remember.

(New Sensor makes EH, Sovtek and Tung Sol reissues, but I'm not sure they are identical in design, etc.)

SOUND “DROP-OUTS” / INTERMITTENT SIGNAL
One Possible Cause

Most (but not all) Mesa/Boogie amplifiers have one or two “cathode follower” tube
stages in their preamps. Tube selection is CRITICAL in these stages.

Specifically, in a 12AX7 tube used as a “cathode follower”, the voltage difference
between that present at the cathode, as compared with the heater voltage, can be
withstood or tolerated by certain types of tubes, whereas other tubes will fail. The
failure of a “cathode follower“ tube will cause sound dropouts or signal loss.

For the past few years, Mesa has been using two types of 12AX7 tubes: ones
originating in Russia (Sovtek EH), and ones originating in China. The Russian (Sovtek)
tube is NOT reliable as a cathode follower. Of the tubes we are using today (March
2008), ONLY THE CHINESE 12AX7 IS RELIABLE AS A CATHODE FOLLOWER.

In conclusion, if you are troubleshooting for signal dropout in a Mesa/Boogie amp,
suspect a cathode follower tube, and try replacing it with a Mesa 12AX7 that is marked
as “CHINESE” (silk-screened on the tube itself).

Below is a partial list of Mesa amps and cathode follower tube locations:

Lone Star & LS Special: V3
M-Pulse: V2
Stiletto: V3 & V4
Venture: V2
Road King I: V3 & V4
Big Block 750: V4
Road King II: V3 & V5
Titan: V4
Roadster: V3 & V5
M2000: V2
Dual & Triple (2ch or 3ch): V3 & V4
Bass 400+: V2
Tremoverb: V3 & V4

ANOTHER POSSIBLE SCENARIO may occur in the “SPONGY” (or on some models,
“TWEED”) power setting: the reduced filament voltage may cause very low output from
a RUSSIAN preamp tube. Again, the recommended fix is to replace the “sagging” tube
with the CHINESE type of Mesa 12AX7 - which are more immune to this type of failure.

 

[4406cuda]

I put in all Tung Sol 12AX7's in mine and it was a great improvement over the JJ's that were in there.

And they are holding up fine? Because apparently Tung Sols blow pretty quick in most CF positions.

They were put in just about a year ago and I play in a band that rehearses and plays gigs at loud volumes. I also put in SED 6L6's at the same time.

 

[Hendog]

I think I found this on Mesa's website. Don't remember.

(New Sensor makes EH, Sovtek and Tung Sol reissues, but I'm not sure they are identical in design, etc.)

SOUND “DROP-OUTS” / INTERMITTENT SIGNAL
One Possible Cause

Most (but not all) Mesa/Boogie amplifiers have one or two “cathode follower” tube
stages in their preamps. Tube selection is CRITICAL in these stages.

Specifically, in a 12AX7 tube used as a “cathode follower”, the voltage difference
between that present at the cathode, as compared with the heater voltage, can be
withstood or tolerated by certain types of tubes, whereas other tubes will fail. The
failure of a “cathode follower“ tube will cause sound dropouts or signal loss.

For the past few years, Mesa has been using two types of 12AX7 tubes: ones
originating in Russia (Sovtek EH), and ones originating in China. The Russian (Sovtek)
tube is NOT reliable as a cathode follower. Of the tubes we are using today (March
2008), ONLY THE CHINESE 12AX7 IS RELIABLE AS A CATHODE FOLLOWER.

In conclusion, if you are troubleshooting for signal dropout in a Mesa/Boogie amp,
suspect a cathode follower tube, and try replacing it with a Mesa 12AX7 that is marked
as “CHINESE” (silk-screened on the tube itself).

Below is a partial list of Mesa amps and cathode follower tube locations:

Lone Star & LS Special: V3
M-Pulse: V2
Stiletto: V3 & V4
Venture: V2
Road King I: V3 & V4
Big Block 750: V4
Road King II: V3 & V5
Titan: V4
Roadster: V3 & V5
M2000: V2
Dual & Triple (2ch or 3ch): V3 & V4
Bass 400+: V2
Tremoverb: V3 & V4

ANOTHER POSSIBLE SCENARIO may occur in the “SPONGY” (or on some models,
“TWEED”) power setting: the reduced filament voltage may cause very low output from
a RUSSIAN preamp tube. Again, the recommended fix is to replace the “sagging” tube
with the CHINESE type of Mesa 12AX7 - which are more immune to this type of failure.

Thanks!