Classic 30 help

[Marshall_Super_100]

Hey guys my brother sent me his classic 30, to mod and fix. The problem that I need to fix is r58 a power resistor blew, so instead of chucking in a new one and sending it back I need find out why it blew and fix it. the caps are draind and it is ready to work on, where do I start, why would it have blown? I have about a year and a half experiance building stompboxes and small amps.

[Marshall_Super_100]

Anyone have help for me? Are there anyother websites I could post on that might be of more help?

[bnwitt]

Of more help than what? Than this forum has been in the less than 3 hours since your first post? It's Sunday. Do your really expect 20 answers in under 3 hours? Have you done a "classic 30" search in this forum? Have you found a schematic online? Have you studied the schematic? Have you done any research at all? Are you interested in learning about the amp or just having someone tell you what to fix? Do you have any idea what the function of R58 is? Why did your brother send this amp to you? Do you have some knowledge of tube amps? I'm not trying to be rude, but you seem a little impatient and like you are expecting someone to tell you which knob to twist without any demonstrated knowledge of the circuit. Are you doing your homework on this job? Start by telling me what R58 does in the circuit. You say you have experience with stomp boxes and small amps, can you tell me what the array of CR7, CR8, CR9 and CR10 in the classic 30 is called? Are R59 and R60 ok? I want to help you but I need to know you really are qualified to work on this amp. Your initial post doesn't convey that.

[Enzo]

Well, I will tell you that the MOST MOST MOST likely reason that resistor would burn up is bad power tubes.

[Eltek]

Hi Marshall Super 100,

I agree with bnwitt about safety, when working with tube amps. It's a little bit more complicated stuff than stompboxes and small amplifiers. Anyhow, no one is born with all the knowledge needed so as bnwitt said, first try to explain what the components do and then you shall get help from more experienced people, who are willing to help you and pass you some knowledge about the fascinating world of electronics.

[Marshall_Super_100]

Sorry I didnt know wheather this site was hot, thought someone might be able to send me in the direction of help, sorry to piss you off beacuse I am new to this and need to get his amp back to him.



Enzo, He didnt send me the tubes beacuse he spent alot on them, they are vintage. Are there any other reasons why it would have blown that I should be considering? or are the tubes the most probable cause?

[Enzo]

Tubes are BY FAR the most likely cause. There is little else in that amp that even could stress that resistor. The cap right after it could be shorted, but that is very seldom the case on these.

I don;t care how old or new the tubes are, tubes are always suspect. They could be really old, and worn out. They could be new old stock that was OK at the sending end, but were dropped in shipping and damaged. Or they could simply have failed at the time he installed them. Without tubes, you can;t even fire up the amp. I mean you can apply power, but it won;t do anything. You can;t even test if your mods or repairs were effective. YOu have to put tubes in it anyway.

Put a set of tubes in it. Charge him for them. If he wants to stick old suspect tubes in it, his chances. At worst your new tubes become spares. But you can then make sure the amp is right, and send it back working.

[Marshall_Super_100]

Enzo,( same name as my relative back in italy name is Enzo) I have tubes to test it with, I had to buy them but no problems with payment on em. Thanks for the help

[rockon1]

Enzo, He didnt send me the tubes beacuse he spent alot on them, they are vintage. Are there any other reasons why it would have blown that I should be considering? or are the tubes the most probable cause?

While were at it does anybody know whether a C30 can use old stock EL84's? The 1+2 pins are tied internally on them. Sometimes newer amps use pin 1 as a tie point since newer EL84's pin 1 is unused. Bob

[Enzo]

Look at the part layout drawing. Pin 1 is not connected on any of the four sockets.

[rockon1]

Look at the part layout drawing. Pin 1 is not connected on any of the four sockets.

Cool. It is something that can sometimes be overlooked when using "NOS" EL84's. Bob