Mesa Boogie Mark 3, Blue Stripe, 1989

N

N_Cook

Guest
Fell over in the van and broke 3 front pot shafts, of course each
compound with push/pull switches, like the other 4 front controls.
"repaired" by someone with a little knowlege is a dangerous thing.
He even managed to break the replacement ones, breaking the
paxolin/rivet joins on switch and pot paxolins. Although correct company
numbering , they are a different flavour , in that the relative
positions of switch and pot are swapped over. Plus 2 cold solderings,
that fell off on first touches.
Plus a piece of mains 15 amp wire bridged across a 10K resistor, with
copper strands fanned out all around.
In the process he's got wires in a complete jumble. So having to start
from scratch, this schematic on botofuckit is the clearest I found ,
despite wrong file name it would seem.
http://i830.photobucket.com/albums/zz227/McBarry01/p2McBarryREDsrtipe.jpg
and p3
Is "lead drive" legend on the amp the same as "drive" on the schematic.?
A 2 terminal useage of one pot is 100K on the schematic but 250K in the
amp here, maybe replaced in antiquity as 1990 datecode and different
batch, but amp was working fine before mishap, so I'll leave at 250K.
The two "bright" designations seem to be clear enough, which is which.
 
On 18/02/2016 14:31, N_Cook wrote:
Fell over in the van and broke 3 front pot shafts, of course each
compound with push/pull switches, like the other 4 front controls.
"repaired" by someone with a little knowlege is a dangerous thing.
He even managed to break the replacement ones, breaking the
paxolin/rivet joins on switch and pot paxolins. Although correct company
numbering , they are a different flavour , in that the relative
positions of switch and pot are swapped over. Plus 2 cold solderings,
that fell off on first touches.
Plus a piece of mains 15 amp wire bridged across a 10K resistor, with
copper strands fanned out all around.
In the process he's got wires in a complete jumble. So having to start
from scratch, this schematic on botofuckit is the clearest I found ,
despite wrong file name it would seem.
http://i830.photobucket.com/albums/zz227/McBarry01/p2McBarryREDsrtipe.jpg
and p3
Is "lead drive" legend on the amp the same as "drive" on the schematic.?
A 2 terminal useage of one pot is 100K on the schematic but 250K in the
amp here, maybe replaced in antiquity as 1990 datecode and different
batch, but amp was working fine before mishap, so I'll leave at 250K.
The two "bright" designations seem to be clear enough, which is which.
Click to expand...

For 1989 ser number in 257** range only take the resistors marked with K
as to be representative, the Cs seem to be correct. None I've tracked
down so far , the R band colours do not agree with that schematic, why 4
band resistors on a valve amp?
 
On Thursday, February 18, 2016 at 2:31:32 PM UTC, N_Cook wrote:
Fell over in the van and broke 3 front pot shafts, of course each
compound with push/pull switches, like the other 4 front controls.
"repaired" by someone with a little knowlege is a dangerous thing.
He even managed to break the replacement ones, breaking the
paxolin/rivet joins on switch and pot paxolins. Although correct company
numbering , they are a different flavour , in that the relative
positions of switch and pot are swapped over. Plus 2 cold solderings,
that fell off on first touches.
Plus a piece of mains 15 amp wire bridged across a 10K resistor, with
copper strands fanned out all around.
In the process he's got wires in a complete jumble. So having to start
from scratch, this schematic on botofuckit is the clearest I found ,
despite wrong file name it would seem.
http://i830.photobucket.com/albums/zz227/McBarry01/p2McBarryREDsrtipe.jpg
and p3
Is "lead drive" legend on the amp the same as "drive" on the schematic.?
A 2 terminal useage of one pot is 100K on the schematic but 250K in the
amp here, maybe replaced in antiquity as 1990 datecode and different
batch, but amp was working fine before mishap, so I'll leave at 250K.
The two "bright" designations seem to be clear enough, which is which.
Click to expand...

Call Westside Distribution, Glasgow. 0141 248 4812
They will identify and sell you the proper pots you require.

The customer pays for parts, don't forget.

The customer doesn't particlarly want to pay for additional labour involving not wanting to buy the proper parts from the manufacturer, however.



Gareth.
 
All working again as far as all of the pots are concerned and 3 of the
pull controls change the sound. No magic smoke or anything overheating.
The pull options of
Treble- Pull shift
Master- Pull deep
Lead Drive - Pull Lead
Lead Master - Pull Bright
no change of sound. It'll be awkward if the "repairer" blew some of the
LDRs, but at least they can be checked for function with a low ps only.
 
In hindsight it should have been obvious why no lead mode.
There is an error on the Mesa schematic of Mesa Boogie 3 on Elektrotanya.
The lead-switch should take the common LDR1 - 4 line, to ground and not
directly shorting those 4 leds as in the diagram, doh!
 
Passed a gig and recording session and no bounce back.
Its quite easy to recondition the original pot+switches , with new stud
ended stem. Much stronger and of course matching action to the others,
unlike the flimsey new pots and of course proper pot/sw positions.
The new pots , nothing stopping any of the tags turning on their rivets,
and they had, at least they've dropped the mains rating of the originals
as these rotating terminals would be utterly unsafe for mains use.
 
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