Mesa Boogie Single Recto V2 Burned Resistor(s) Help !

[moshpit903]

Hi,I am a newbie here but active on a few other forums but I believe this might be where I need to be,so here goes..

I had a new amp for 1 week but always wanted some kind of Mesa Boogie Rectifier and realized I don't need the Dual or Triple Rectifier due to 100w-150 watts,and my ragged back,so I traded for a Single Rectifier Solo head V2 2 weeks ago and already have a problem.
The amp sounded ok for about 3 hours total time then the problem came to the clean channel,no volume with the Master and Output controls dimed,just some noise,so I did the tap on a tube with chopsticks test and V1 preamp tube was immediately found,so I replaced the tube and the same thing,just some noise.
I took the chassis out and drained the juice out of the caps,then I visually inspected around V1 and I saw it,1 burned resistor,and the single resistor on opposite sides have a minor charring on them,so they are still in there for now but need to be replaced as well.
I removed the charred resistor and I can't see the resistors value because it charred enough to where the value is gone,and on this pcb thats where the resistors value is,which I have never seen before because I have repaired my XXX amp head and a Jet city amp head and several others and all the info was right next to the where the part was located on the board,like R95, C26 etc etc.
I have downloaded the Mesa schematic for this amp but I don't understand it at all,its written out in freehand and I guess i'm too stupid to understand it,so I was hoping somebody,anybody here with knowledge of this amp or how to read schematics I would greatly appreciate any help,I would be willing to pay for your time and effort !
I spoke to Mesa Boogie this morning by telephone and the man told me they don't carry the boards anymore so I am freaked out now..I have cleaned and inspected this pcb and it just needs the proper resistor so I can actually enjoy the amp instead of just stare at its internals.
The Mesa tech was supposed to call me back today with the info and he never did so I am stuck now..what would you do,ask for help or smash it ? There are no techs within 200+ miles from me and I can do the work with the right info.
Any info would be greatly appreciated !!

[The Dude]

Firstly, welcome to the place!

Do you have a schematic? If so, please upload it so we are all on the same page. If you found a burnt resistor near V1, my best guess would be that it's a plate resistor for V1 and likely caused by a bad tube. Measure plate voltages at the V1 socket (pins 1 & 6) and post the results here. If there's no voltage on one of those pins, it will confirm my suspicion.

[moshpit903]

Firstly, welcome to the place!

Do you have a schematic? If so, please upload it so we are all on the same page. If you found a burnt resistor near V1, my best guess would be that it's a plate resistor for V1 and likely caused by a bad tube. Measure plate voltages at the V1 socket (pins 1 & 6) and post the results here. If there's no voltage on one of those pins, it will confirm my suspicion.

I will do that,I just edited my post with 3 imgur pictures and working on getting the part of the schematic which I believe goes to V1. actually I don't see my pics now,it just showed the img place to click on them.

[moshpit903]

I will try the 3 imgur pics here again..also I will need to re-assemble my chassis to do the reading due to having to ge to the backside of board to remove the solder to remove bad resistor,the resistors are just about laying on the pcb on this amp.



I don't see my pics here and I have put the url in 4 times now..not sure what to do now.

[The Dude]

Well, if you have it torn down already, no need to reassemble it. Just follow the trace or use a meter to see which tube pin the resistor goes to. Check from the traces where the resistor was to tube pins until you find continuity.

[moshpit903]

Well, if you have it torn down already, no need to reassemble it. Just follow the trace or use a meter to see which tube pin the resistor goes to. Check from the traces where the resistor was to tube pins until you find continuity.

Yeah that sounds better,I will do that real quick,I have been on this amp for 3 straight days and nights and gotta shut down soon for the night and then start early tomorrow am.

[moshpit903]

Ok I just got the schematics sized down to 70% on Imgur and will try again here,if these don't load this time I don't know what else to do.
I actually downloaded the schematic from this website last week from an older Single Recto post..so here goes,and I will check back tomorrow morning..thank you for all your help now and any later !

[Jazz P Bass]

This may be the schematic: Mesa Boogie Single Rec_ Solo 50_sers2.pdf

[moshpit903]

This may be the schematic: [ATTACH]51499[/ATTACH]

Yes thats it ! I got it from here but I guess I am not sure how to convert it to jpg,jpeg,png,or a gif like it says when loading a URL..so everything I have done to load pics here has been wrong..And I thought I knew something !
Thank you for getting that to here ! Heck when the Mesa Boogie man didn't call me back I bummed out..this amps in great condition with a few bad resistors..I don't want to write it off,especially for what I traded it for !
I am looking at my copies of the schematic and I can't figure this one out,I see V1a and V1b but not the correct resistors..I have the value of the 3 other resistors in the same area except the one I need..
I have in order from left to right..a) 100k B) 22k C) ? D) 39k written on the board but my reading of the resistors bands off a color chart shows 39.5k ..I am missing #c).

[moshpit903]

I have just now had time to log on here in 2 days,been working mainly outside on other projects but I have an update on progress on the Recto.
Monday night after logging off here I couldn't sleep so I was all over the internet looking for anything and I got lucky and found 5 "gut shots" of Single rectifier version 2 like I have,so for 2 hours I compared all resistors and caps etc on the boards and mine was like theirs,so I checked the 5 band resistors resistors in the V1 area and came up with 39.2 k 1%..the Mesa Boogie repair tech had sent me an email late saying they were all 1/2 watt resistors so I researched and finally found what my amp needed,then placed the order for parts,which was very time consuming finding the proper resistors and values,but I/we got it done and as of right now I have replaced and soldered in the 3 main resistors and double checking my solder joints,then going to clean and then re-assemble the amp and hope like heck I got it done.
More info later ! Thanks to all here !

[Randall]

Two things. First, I have never seen a 39.2 K resistor, and 1% is pretty unusual. So, I think you're off there. Second, those resistors burnt for a reason, so simply replacing them without correcting the actual problem, bad tube probably, isn't fixing it. OK, three things. You need to slueth out what those resistors are connected to as mentioned already. Admittedly, it's a Mesa, and that can be a lot harder to do than say, but if you don't know what it's function is, how are you going to correct the actual problem?

[The Dude]

I agreee with Randall. You need to find out where the resistor is in the circuit. Otherwise, it may just burn up again. Resistors do burn for a reason. They don't just go bad. That said, the only 39K I can find on the schematic is off the cathode of V2b. It would be easy enough to verify that with a meter (resistor pad to V2 pin 8). If that is the right resistor, I'd probably change V2 also. Also, it's just a tube amp. There's no need to worry about 1% or .2 ohms. Anything close to 39K will work just fine.

[moshpit903]

I will try to answer both of you now..I did leave out a few things instead of started a biography on this amp..i did take the tube socket off,I checked continuity down all the traces I could find by bare eye and with a flashlight looking through the pcb. for me it all looked good.
The resistor in the original posts picture in 2015 showed a picture of the spot where the burned resistor was,and to the right of it the pcb has 39 on the pcb and its the same resistor as the burned one is,so this 39.2k resistor is a 5 band resistor that is from top to bottom..Orange,,white,,red..Black..Brown..according to the 10 5 band resistor charts I looked at thats 39.2..also the man at Mouser electronics looked it up and spent 15 minutes with me on the telephone talking about it..the Mesa Boogie tech Rich emailed me and says '' almost all of the resistors on our Solo 50 parts list are 1/2-watters,and that looks like what I see in your pictures,so I say: 1/2 watt. so I went with what he said,what I saw on the resistor band charts and the Mouser electronics tech and ordered the 39.2k 1/2 watt resistors..
I also removed the other 2 bad resistors on my amps pcb.they are 100k and 22k 1/2 watters..so I think I got the right resistors..I could be wrong but I guess I went with people that have worked on and at Mesa for some of my info..and what my pcb and the others show in the picture(s).
Now I did put the amp back together and turned it on and it blew the main fuse twice,so thats it for me on this amp..i will call the techs in Dallas 200 miles away from me and drop it off and let them fix it..i was hoping I would actually get lucky for once in my life,but I was proven wrong again.
Thanks for all the help music-electronics forum members.

[moshpit903]

Just when I/you thought I am a quitter I can't stop thinking about this,i know I can fix it myself and will do it..things I have done since my last message are..

1) On the original picture of V1's resistors the other guys and mine have 39 printed on pcb to the right of the burned resistor,and I have re-checked the 5 band resistor charts and see I made a mistake,but the original resistors 5 bands add up to 39.2.not the 39 printed on my amps pcb or the original poster of this thread from way back in 2015.

2) My mistake on the resistor is the 5 bands add up to 39.2 ohms but not 39.2k,so I believe I made a mistake there and figure thats part of the problem,but still why has Mesa Boogie printed 39 on the pcb and have 39.2 resistor installed ? I may be wrong there so let me know if thats a major deal,which I think it is..Whoops, Damn I see where you The Dude said 1% or.2 ohms is nothing to worry about,so forgive my rambling on,I am just bummed,I traded a nice new amp for this one and was only expecting to be jamming,not here or any forum begging for help !

3) I did not order a new tube socket before I put it back together this time so I found the correct type and ordered 2 of them,and also ordered 39 ohm 1/2 watt and 39.2 ohm 1/2 watt resistors.. Rich,the tech from Mesa Boogies said these are 1/2 watt resistors so I orderded as per what he said they were.

4) I actually hate electrical work,and have traded in several good cars in for others due to electrical nightmares,but I have actually done at least ok with the projects I have taken on,but this ones bothering me,but I will fix it properly or eventually go the tech route.

5) I have 15-17 good preamp tubes to use for when this amp goes back together so I am sure most if not all are good because I have swapped a few in and out of my other amp,an EVH 5150-350 watt head.

6) I will look back at all the info you all have given me, and when the new tube socket comes in I will dis-assemble this thing and go all the way through it.

7) The parts man at Mesa Boogie told me that they didn't have any boards for these 50 watt Single,Tremo or Recto verbs,and said that "all pcb's can be repaired".so we'll see..I believe I shut mine down before it really did too much damage,before it was blowing fuses so going to give it another try.

[The Dude]

Instead of guessing whether it's 39 ohm or 39k ohm or whatever, please find out where it is in the circuit and we can look at the schematic and see what it is. Take a meter, set it to low ohms scale or diode check or continuity beep and measure from the traces where the resistor goes to each pin of the preamp tubes and find out what pin and what tube it goes to. If you put in the wrong value resistor, you could do more damage or the amp won't work right. There's no need to guess. Also, I have to ask,...... why are you changing tube sockets? Is there evidence of arcing or something we don't know about?