Mark V different versions?

The Boogie Board

Help Support The Boogie Board:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Thanks Bandit. So....... Which one should be there n which one shouldnt ? :oops: I have no clue really..
 
The early version did not have the 82.5k resistor (has the gray red green brown stripes).
Instead, just below C18 you would see the 330k resistor (orange orange yellow) and a 56k resistor (green blue yellow-unless it is a 1% it would be 56.2k green blue red red brown). Not sure what text would be on the PCB near the Mesa Boogie name.... To change to current (assuming no further changes were made) would be a bit more dramatic. Change one part (not fun since it is lead free solder) and remove another to tack on a cap and resistor to run parallel. Note that I am only assuming these are the parts in question since they match the sequence and values. I also think the 330k and 100k complete the circuit to ground. Old version had a 470k instead of the 330k. Now comes the question were there any changes to the switching network (relays and logic circuits that are not in print on the schematics- at least on the original version that is easy to find on the net).

Only a Mesa Certified tech could answer the questions what has changed. That will not happen as they would prefer to keep there certification and not provide any details due to any binding contracts or disclosures for non-compete or discuss any intellectual property of the design.

Some minor changes will take places as problems arise. If it is just a component change then the PCB will remain the same. Sometimes there are extra patterns on the PCB that are not populated. Could be an oversight and left as a fix or alternate circuit if the prototype had both as it does not cost anything to leave it there except for real estate. For the case of the change between 2009 and 2010 that was a board change since the C18 circuit path was altered and reconnected to the wiper path of the pot vs the high side.

I am not in favor of modifying the amp or anything of that nature unless it is absolutely necessary. I will however replace failed components and repair circuit traces that fail to keep thins running as they should. It the amp has a warranty, it will go back to Mesa for repair (I have to ship it since there are no service locations anywhere near where I live).

Since I have the 2010 change, the amp is still brittle but for a different reason. Makes me want to trade in but first buy a new one to compare and then sell the old one if one sounds better than the other. Better yet not buy any models of a certain year...... Keep in mind this is one reason it is not announced that there have been revisions..... except for the case with the JP-2C as it came with a notice and a disclosure that described a change during production that was different than the original version and a deviation from the Mark IIC+ circuit relating to the clean channel and FX loop send level control. Mesa does make changes but it is not mandatory that they publicize it except to the repair techs.
 
I guess the question now is this: Does anyone with a very early Mark V want to take a look inside and see if they've got the older config?
 
APEMAN said:
Yes there are changes in the schematic, I think there is at least one big change in CH3 preamp.

170624mkvs.jpg


The very early amps sound different!

Weird, part of this change also seems to be maybe running counter to what they said about the internal volume control:

In the top circuit there's 386 KOhm in the top and 570 KOhm on the bottom, which reads like 7.5-7.75ish on the Volume knob on an audio taper pot (which I'm assuming volume was?)

In the update, it's 550 KOhm over 430 KOhm, or like 6.9-7ish on the internal Volume. Which doesn't sound like much, but on a log taper pot between 6 and 9 is the range of 30-90% of the resistance.

So when the manual reads that the internal volume is set to 7.75, it looks like after this tweak it's actually more like 7 on the dot. Because so much range of resistance exists between 7 and 8 as well, that's probably why the originals were so sensitive in that "magic range".
 
APEMAN said:
Bankim said:
So....... Which one should be there n which one shouldnt?

Hey Bankim, please be cool and let your soldering iron cold until we know more :) Could be the case, that further revisions of the schematic between the two known from 2009 and 2010 exist - the tone stack update could have been done earlier than you think. What we know is that there have been at least two updates to the power supply, mute and switching in the <#12XX range. Mesa put out a service manual for technicans to procede some updates to those amps to garantee stable performance.
To your question, the standard version should contain the 82k Restistor R218.
Cheers :)

Apeman, Thanks for the information.

Oh, you dont have to worry about me opening up the amp chasis. I couldn't even if I wanted to ... LOL
 
The newer ones have a different Footswitch.
Mine looks like this (S/N 013XXX):

Mark_V_Footswitch.jpg


They came up in the time of the "little Mark Vs".
 
It sounds like the circuit change happened early in the Mark V, maybe first year. The footswitch change seems to be more recent, so I wouldn't assume the schematic and footswitch change correlate, other than the new footswitch definitely being the new schematic.
 
IronSean said:
Weird, part of this change also seems to be maybe running counter to what they said about the internal volume control:

In the top circuit there's 386 KOhm in the top and 570 KOhm on the bottom, which reads like 7.5-7.75ish on the Volume knob on an audio taper pot (which I'm assuming volume was?)

In the update, it's 550 KOhm over 430 KOhm, or like 6.9-7ish on the internal Volume. Which doesn't sound like much, but on a log taper pot between 6 and 9 is the range of 30-90% of the resistance.

So when the manual reads that the internal volume is set to 7.75, it looks like after this tweak it's actually more like 7 on the dot. Because so much range of resistance exists between 7 and 8 as well, that's probably why the originals were so sensitive in that "magic range".

I still find it curious that Mesa continue to leave out the vol 1 control. It seems far more critical to the tone than something that you'd do away with. For the V, it's often considered to not have enough gain (although I disagree). For the V:25 it was raised by 0.5-0.75 and the amp is often described as a fire breather. JP's amp has an entirely separate channel and integrated pull pots, just for 1.0 value of more vol 1. Why wouldn't they just bring the pot back into the design? I haven't used a Mesa with the vol 1 pot so I can't comment on how hard it was to dial in but I'm not sure I buy into the reduced tweaking as the reason. Surely tonal variety outweighs the 'inconvenience' of turning an additional knob. The mark amps are renowned for the tweaking. And don't want to speak for everyone, but as far as I can tell, we love the tweak. What fun is it if you don't have to turn any knobs to get to your glorious settings.

If it is a matter of space, the mid control seems are a far more redundant or least valuable control when it comes to impact on tone. Despite the fact that I use it and usually max it out, if I had to choose one or the other I'd probably go with vol 1 and settle for whatever preset mid was determined, given how slightly it impacts the tone. Ideally I'd rather have both in there.

Anyway, just my thoughts and rants. Not sure If I'm alone on this. As much as I don't like to admit it, half of my motivation for getting a JP when I have a V (which I love), is that it goes to 9. And I wonder how much of the glowing reviews on the JP is largely driven by the increase in vol 1. I'm sure the rest of the features will blow me away and the tone will be different, more organic etc etc, but still... 9 vs 7.

Does anyone else share this view? Maybe I'm just getting a little bit spinal tap, I don't know.
 
potentiometer_taper.png


I actually think it's a pretty big deal. Especially if you look at how audio taper pots work:

Volume at 5 is only 10% signal passing.
Volume at 7 is 50%
8 is 70%
9 is 90%

So if I understand correctly there's a vast range of signal amplification between 6 and 9 on volume 1, which plays a lot into the range of sounds.

I've got a studio preamp I tried running into my Mark V power section to compare last night, but I think I need to deoxit the pots or jacks as I found getting the volume above 7 suddenly dropped the signal. So I'll try and get some real hands on comparisons once I do a little maintenance.
 

Latest posts

Back
Top