Members potaetoes Posted January 26, 2009 Members Share Posted January 26, 2009 disclaimer: i'm a dumbass and forgot to check the value and taper of the pot. BUT, it should be somewhat higher than the resistor it replaces. anyway, here's the amp here's the knob here are the three wires that connect it to the PCB here's a shot of the other side of the PCB, taken through the V1 cutout, where you can see R292 is missing. also (important), you can see the trace is cut between the solder points for the yellow and orange wires. you could probably perform this mod without even removing the PCB from the chassis... anyway... anyone who was interested in this mod, there ya go! Link to comment Share on other sites More sharing options...
Members Clinically Deaf Posted January 27, 2009 Members Share Posted January 27, 2009 I've always liked that amp. How much do they run these. I'm thinking of grabbing one of those or maybe .50 cal to A/B with my JCM 800 Link to comment Share on other sites More sharing options...
Members chris_d Posted January 27, 2009 Members Share Posted January 27, 2009 Very cool, that would be this resistor here then: If you take the knob off of that control you can probably read the value off of it. It should be printed on the pot. I would guess that it is either a 500k or a 1M. Thanks for the pictures! -chris Link to comment Share on other sites More sharing options...
Members potaetoes Posted January 27, 2009 Author Members Share Posted January 27, 2009 they're usually $450-550 in good shape. i paid $475 for mine exactly as you see it, with the original footswitch. prices do seem to be going up a bit lately, though. Link to comment Share on other sites More sharing options...
Members potaetoes Posted January 27, 2009 Author Members Share Posted January 27, 2009 Very cool, that would be this resistor here then: If you take the knob off of that control you can probably read the value off of it. It should be printed on the pot. I would guess that it is either a 500k or a 1M. Thanks for the pictures! -chris that's the one. i'll check the pot value later tonight... no time right now. Link to comment Share on other sites More sharing options...
Members jeid2000 Posted January 27, 2009 Members Share Posted January 27, 2009 Can this be translated to the .50 Caliber+ yah? Link to comment Share on other sites More sharing options...
Members chris_d Posted January 27, 2009 Members Share Posted January 27, 2009 Can this be translated to the .50 Caliber+ yah? As far as the one .50 schematic i have seen, yeah, it looks like the same setup for those gainstages. Should be the same deal, as far as i know. -chris Link to comment Share on other sites More sharing options...
Members potaetoes Posted January 27, 2009 Author Members Share Posted January 27, 2009 Can this be translated to the .50 Caliber+ yah? yes. not sure if it's the same resistor number, but the mod is exactly the same for the .22+ and .50+. it can also be done to the .22 and .50, but i don't know if it's in the same place on the PCB or not. Link to comment Share on other sites More sharing options...
Members chris_d Posted January 27, 2009 Members Share Posted January 27, 2009 yes. not sure if it's the same resistor number, but the mod is exactly the same for the .22+ and .50+. it can also be done to the .22 and .50, but i don't know if it's in the same place on the PCB or not. As far as the schematic for the .50 is concerned, the resistor # is the same and everything. The whole preamp looks just about identical between the two. -chris Link to comment Share on other sites More sharing options...
Members newholland Posted January 27, 2009 Members Share Posted January 27, 2009 sure nuf is the same, from everything i've been told by mesa. it's really too bad i didn't have this mod done on my .50! sure looks like a damn snap.. did you have any idea what the other mods that were done were either? i'll have more confirmation on THAT mod-- although this sure seems like enough to get it off the ground- on thursday. i scheduled a quick blab with one of the techs at mesa-- so i'll get the skinny as to anything else that they might've done as well! thanks a TON for posting that-- could well've saved my ass! i'm gonna have to watch my soldering iron near that 3300uF cap, i think.... meanwhile-- thanks also for the BADASS documentation job of terminal leads as well.. i freakin' owe you big, man! Link to comment Share on other sites More sharing options...
Members Bubbluz Posted January 27, 2009 Members Share Posted January 27, 2009 Is this do-able on the old .22's that only have the volume and master controls / no EQ ? My lead channel is gain heavy as well.I haven't done any amp mods myself,but I have a guy that does. Link to comment Share on other sites More sharing options...
Members newholland Posted January 27, 2009 Members Share Posted January 27, 2009 Is this do-able on the old .22's that only have the volume and master controls / no EQ ? My lead channel is gain heavy as well.I haven't done any amp mods myself,but I have a guy that does. the .22+ isn't a + because of the eq-- its more an updated circuit. i believe it's the same to a large extent though-- google up the schematic! but i'd bet you could. Link to comment Share on other sites More sharing options...
Members primeholy Posted January 27, 2009 Members Share Posted January 27, 2009 Guy I got mine from was the original owner:lol: He got it modded by Mesa. You can see in the pics they put the reverb and precence in the back and turned the re and pre into lead drive and lead master on the front. Link to comment Share on other sites More sharing options...
Members potaetoes Posted January 27, 2009 Author Members Share Posted January 27, 2009 there you go, definitely can be done to .22/.50 as well... though you'd probably want to start with the lead master before bothering with the drive control. it's too bad mesa doesn't just make something like an updated ".22++" with lead drive control on the front. i'd be first in line to buy one of those little suckers. Link to comment Share on other sites More sharing options...
Members vic Posted January 27, 2009 Members Share Posted January 27, 2009 what does this mod do?? Link to comment Share on other sites More sharing options...
Members potaetoes Posted January 27, 2009 Author Members Share Posted January 27, 2009 what does this mod do?? it adds a knob to control the drive of the lead channel. in stock form, the "volume" knob determines the gain for both channels. a lot of people feel that when the volume is set for good clean tones, there's way too much gain on the lead channel. if you turn the volume down for less gain on the lead channel, the cleans can get a little anemic and weak. adding a separate lead drive control solves that problem. Link to comment Share on other sites More sharing options...
Members ke2 Posted January 27, 2009 Members Share Posted January 27, 2009 Very cool stuff, potaetoes!! I have a cal 50+ that probably would be more versatile with this mod too Link to comment Share on other sites More sharing options...
Members rickou812 Posted January 29, 2009 Members Share Posted January 29, 2009 Thanks for the instructions. How is the mod performed as shown in post by primeholly that adds a lead master and a lead drive? Link to comment Share on other sites More sharing options...
Members newholland Posted January 29, 2009 Members Share Posted January 29, 2009 ARGH... mesa customer service lied to me... i gotta wait til monday to get the tech on the line... regardless.. i'll update this as soon as i get the skinny, and do a photo tour of the amp guts for all the .22/.50 guys out there! Link to comment Share on other sites More sharing options...
Members rickou812 Posted January 29, 2009 Members Share Posted January 29, 2009 ARGH... mesa customer service lied to me... i gotta wait til monday to get the tech on the line... regardless.. i'll update this as soon as i get the skinny, and do a photo tour of the amp guts for all the .22/.50 guys out there! Thanks for the update..of sorts..lol How did the tech lie?, Just out of curiosity.. And the photo tour would be awesome Link to comment Share on other sites More sharing options...
Members newholland Posted January 29, 2009 Members Share Posted January 29, 2009 Thanks for the update..of sorts..lol How did the tech lie?, Just out of curiosity.. And the photo tour would be awesome oh-- i was just kidding-- they didn't lie at all! mesa service is awesome-- they thought the guy who i could talk to would be in today, but he's not in til next monday... so nobody lied at all- they just got confused over his schedule. i's just being overdramatic... it is hilarious though that only one person knows the mod, and it's not documented in their records! the secret key is being transferred... i shall be the documentor of the magick.... Link to comment Share on other sites More sharing options...
Members rickou812 Posted January 29, 2009 Members Share Posted January 29, 2009 oh-- i was just kidding-- they didn't lie at all! mesa service is awesome-- they thought the guy who i could talk to would be in today, but he's not in til next monday... so nobody lied at all- they just got confused over his schedule. i's just being overdramatic... it is hilarious though that only one person knows the mod, and it's not documented in their records! the secret key is being transferred... i shall be the documentor of the magick.... Your da man!! can't wait till monday now... Link to comment Share on other sites More sharing options...
Members newholland Posted February 3, 2009 Members Share Posted February 3, 2009 alright: update. got hold of mesa, and the actual factory mods. having discussed the actualities of it, and reviewing tater's pics (thanks chris_d! co-conspirator in electronic debauchery)-- the skinny is as such. the 470k resistor (r292) isn't just REMOVED-- in fact, it's swapped out for a 1 meg resistor. oddly-- that's MISSING from potatoes' amp! i dunno if they changed it somewhere along the way-- but it seems to not be there! in any case-- the new 'sanctioned' mesa mod has a one meg in the r292 spot, and a one meg pot in parallel. the one thing that isn't as apparent from the pics at first glance is that the trace right after r292 is CUT. you CAN see it-- but i'd missed that detail-- and it's VERY well documented on my schematic from mesa in a note on the diagram. anyhow-- i'll get into it a little later this weekend-- but schematic in hand-- almost ready to go! more soon... Link to comment Share on other sites More sharing options...
Members rickou812 Posted February 3, 2009 Members Share Posted February 3, 2009 alright: update.got hold of mesa, and the actual factory mods. having discussed the actualities of it, and reviewing tater's pics (thanks chris_d! co-conspirator in electronic debauchery)-- the skinny is as such.the 470k resistor (r292) isn't just REMOVED-- in fact, it's swapped out for a 1 meg resistor. oddly-- that's MISSING from potatoes' amp! i dunno if they changed it somewhere along the way-- but it seems to not be there!in any case-- the new 'sanctioned' mesa mod has a one meg in the r292 spot, and a one meg pot in parallel. the one thing that isn't as apparent from the pics at first glance is that the trace right after r292 is CUT. you CAN see it-- but i'd missed that detail-- and it's VERY well documented on my schematic from mesa in a note on the diagram.anyhow-- i'll get into it a little later this weekend-- but schematic in hand-- almost ready to go! more soon... Thanks for the update. Is there any way you could post up the schematic? Link to comment Share on other sites More sharing options...
Members flanging_fred Posted February 3, 2009 Members Share Posted February 3, 2009 I tamed the lead channel on my .22 by putting an old NOS mullard 12au7 in the v1 valve/tube slot. It worked really well and reduced the gain to a manageable level. It did make the amp a bit quieter but for me that was a good thing. 12au7's can still be had cheap on ebay, I paid about Link to comment Share on other sites More sharing options...
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