JCM 800 2203 dead...

[stokes]

Mitch,like I have been saying I am not trying to be insulting in any way,look at the 5150 thread,I was not saying it is a stupid question,but lets look at how you got there.You took a working amplifier and are trying to do a pretty drastic mod to it,you apparently blew a screen resistor or if the resistance measurements you gave are correct the inner 2 screen res at least.And you dont even see that,you are insisting the inner ones have to be fine because the outer ones sparked.This is where getting in over your head comes into play.You had no tubes in the amp when something blew,you obviously wired something very wrong in moving those sockets,and it is not just a matter of making a newbie mistake and its like oops.You wired something with a lot of power to something wrong,and if it was wired to the "right" wrong place you could kill yourself.None of here can tell you what you wired wrong,we dont have the amp in front of us,and if you cant see or dont know where to look at the wires you ran yourself,then I am afraid you are in over your head,and what I meant by, knowing just enough to get into trouble.When I asked about that mystery cap,you said it paralleled into the preamp somewhere,when it is actually in the power stage on the PI,you were also refering to it as cap V,as if it were in the end of the B+ rail when it is the third cap in the line.This is very basic amp stuff,I know you say you want to learn and that is why you are here,but I dont want to see you kill yourself.If you wire something wrong doing that cap job,you could do just that.Be careful.As for books,look for some of the old military electronics manuals.Since you are interested in tube circuits these may seem old but they have a lot of good basic stuff,and in the world of electronics,tubes are very basic.http://www.pacificrecone.com/JackDarrBook.html this link is to Jack Darrs old amp manual,very good book.I've never seen the Kevin O'connor books,but I've heard good and bad reviews.I have read Gerald Webers books,but you will need to know the basics to follow him.There is a book I have from years ago from the Navy series from the '40's or '50's called Basic Electronics,pretty much all the tube stuff you would need to know.I think you might find that one on ebay from time to time.Study tube amp schematics,start with the basic champ type circuit,these will show how all tube amps operate basically.Then as you look at some more complicated schems you will see how similar they are to the basic Champ circuits,and how the basics of tube amps are all pretty much the same.The internet is full of info,as you know,but be careful,there is as much misinformation here as well.Thats where a book like Basic Electronics comes in handy,you can sort out the BS.You really have to get the basics down before you dive into the bigger problems.I appologize if it sounds like I am "coming down on you",but I really dont want to see you hurt yourself,or your amps,I know in learning you will inevitably fry things from time to time,and you already said you would fry this amp over and over to learn,but dont fry yourself in the process.

[MitchK]

Mitch,like I have been saying I am not trying to be insulting in any way,look at the 5150 thread,I was not saying it is a stupid question,but lets look at how you got there.You took a working amplifier and are trying to do a pretty drastic mod to it,you apparently blew a screen resistor or if the resistance measurements you gave are correct the inner 2 screen res at least.And you dont even see that,you are insisting the inner ones have to be fine because the outer ones sparked.This is where getting in over your head comes into play.You had no tubes in the amp when something blew,you obviously wired something very wrong in moving those sockets,and it is not just a matter of making a newbie mistake and its like oops.You wired something with a lot of power to something wrong,and if it was wired to the "right" wrong place you could kill yourself.None of here can tell you what you wired wrong,we dont have the amp in front of us,and if you cant see or dont know where to look at the wires you ran yourself,then I am afraid you are in over your head,and what I meant by, knowing just enough to get into trouble.When I asked about that mystery cap,you said it paralleled into the preamp somewhere,when it is actually in the power stage on the PI,you were also refering to it as cap V,as if it were in the end of the B+ rail when it is the third cap in the line.This is very basic amp stuff,I know you say you want to learn and that is why you are here,but I dont want to see you kill yourself.If you wire something wrong doing that cap job,you could do just that.Be careful.As for books,look for some of the old military electronics manuals.Since you are interested in tube circuits these may seem old but they have a lot of good basic stuff,and in the world of electronics,tubes are very basic.http://www.pacificrecone.com/JackDarrBook.html this link is to Jack Darrs old amp manual,very good book.I've never seen the Kevin O'connor books,but I've heard good and bad reviews.I have read Gerald Webers books,but you will need to know the basics to follow him.There is a book I have from years ago from the Navy series from the '40's or '50's called Basic Electronics,pretty much all the tube stuff you would need to know.I think you might find that one on ebay from time to time.Study tube amp schematics,start with the basic champ type circuit,these will show how all tube amps operate basically.Then as you look at some more complicated schems you will see how similar they are to the basic Champ circuits,and how the basics of tube amps are all pretty much the same.The internet is full of info,as you know,but be careful,there is as much misinformation here as well.Thats where a book like Basic Electronics comes in handy,you can sort out the BS.You really have to get the basics down before you dive into the bigger problems.I appologize if it sounds like I am "coming down on you",but I really dont want to see you hurt yourself,or your amps,I know in learning you will inevitably fry things from time to time,and you already said you would fry this amp over and over to learn,but dont fry yourself in the process.

I obviously wired something wrong I can understand that because if I didn't then nothing would be happening. But understand that what I did was make no change to the actual circuit of the pcb board, this is all just physical stuff. I connected the switch to those diodes and thats it, and I really really can't see how that would cause the problem. because like I said i unsoldered the sockets from the board put a 5 inch length of wire in their place on the pcb and attached the other end of the wire to the sockets. NOW, clearly there is more going on than that, I understand that I fully agree with that. I want to know if whats happening is symptomatic of something. evidently a short would be the answer, but what I'm curious about is why would the sparking/burning happen right at this one particular pin? especially since I still have the standby on as far as I can see (the 5150 schem is pretty hard to read for me) it really shouldn't even be connected to the mains because the standby switch is in its way, would there be any likely place that it I could have accidentally shorted it out? any place more likely than another is what I'm asking. as for the resistors, I'm not insisting anything, I'm putting out my assumptions, what i'd assume would be the case, and the reason I'm putting those out is because I don't have a lot of faith in them, because I don't know a lot about this stuff, I assume my assumptions are usually flawed, but its better than just not even mentioning or checking the middle sockets if I thought my assumptions were correct. Show me how my assumptions are flawed and next time I'll be better equipped to make a more reasonable one.

As for "cap V" and for it "being at the end of the B+ rail etc" that is an assumption you are making, not me. I took a picture of the inside of my chassis and put a random number on each one, naively I'll admit, thinking you'd just know which one was which, because to be perfectly honest I didn't know even with the amp in front of me, I have no qualms admitting that, but now I at least have a better understanding.

I've got military manuals but I find they are not very useful. its not for a lack of trying, i'm an avid reader, but I don't know I think they would be really useful books if you already knew. I need pedagogical simplification.

thanks for the link though it looks really promising I'll be reading it over the holidays for sure

[stokes]

As for the cap V thing, this is part of what I am talking about with basics.If you start off describing the power rail as cap I being the main,cap II being the screen it stands to reason that cap III,IV and V follow down the line,this is basic.Look I am not trying to discourage you,but you have to get the basics down,going to the 5150 thread,if you bypassed those suppressor diodes as you describe,that is not an oversight,it is not just some simple mistake,that is just not having enough info to know not to ground your plates.Very basic tube knowledge.If you dont know what both ends of something are connected to dont touch it.Maybe you didnt actually ground those diodes, but to say you bypassed them means only one thing,you grounded them.If you just used the wrong terminology,again we get back to basics, or the lack of.I think you are just getting in over your head,its like you bypassed the basics to get to the good stuff and that will only lead to trouble,and I cant stress enough the fatal results that could occur.Just be careful.That Jack Darr book was considered the "holy grail" of tube amp repair manuals in the day.I know I am dating myself,but that was the first guitar amp book I read,after reading the Basic Electronics book.As for the other military manuals,you have to get the older versions from the "40's,'50's and '60's that deal with tube circuits.And once you know the basics you will see that they are very relevant.Seek out that Navpers Basic Electronics,the copy I have is from 1955,it is marked Navy Training Courses-Navpers 10087.It has everything about every tube circuit,everything in a guitar amp is in there.Between this one and the Jack Darr manual you will have a good starting point with plenty of basic info.Start with smaller more basic projects,jumping right into the power supply before you know what every connection and component is for is dangerous.Be careful.