Did my 5150 just die?

[AntonioPetrole]

I turned on my 5150 last night and let it warm up for a minute on stand by. Typically if I don't let it warm up at least 10 minutes, there are a few pops that come through and the tone sounds kind of weak and weird. I only let it warm up for a minute last night (I just wanted to record a quick riff) and it sounded kind of weird. After a minute or two of playing, the sound just faded out in a few seconds. The standby light stayed off no matter what position I put it in, so I turned it off hoping it would be fine.

I don't want to turn it on until I am familiar with exactly what might have happened. Any ideas? I would think (not that I know anything about amp repair) it is just a power tube that died but I'm not sure. Btw this is my 5150 combo if that helps.

 

[colonel kurtz]

the fact that it usually needs to warm up for 10 minutes or more sounds like there was already some sort of issue going on...but if you're lucky, it's just a fucked up tube. could also be a power transformer issue...but i don't think those are too common in 5150 amps. could also be a leaky/burned capacitor somewhere, that always causes all kinds of weird and random shit to happen.

 

[AntonioPetrole]

the fact that it usually needs to warm up for 10 minutes or more sounds like there was already some sort of issue going on...but if you're lucky, it's just a fucked up tube. could also be a power transformer issue...but i don't think those are too common in 5150 amps. could also be a leaky/burned capacitor somewhere, that always causes all kinds of weird and random shit to happen.

I bought it from the dude who does Jaded Faith Mods and he said he just serviced it/retubed, that was only 4 months ago so I took his word for it.

Is there any way for me to look inside and see what might be wrong?

 

[greyskull]

Sounds like power amp valves are gone, also there is a fuse on the main board which may have popped too.

 

[Sloan]

If you've got a power/standby light out, start by checking fuses.

 

[sprack]

While you have it open also check the resistors around the power tube sockets for burns. The screen grid resistors are under-rated by default and prone to go.

 

[AntonioPetrole]

So I just got home and opened it up. Nothing really looks funky to me (I'm no means an electronics expert or even amateur haha).

Fuse on top

I have no idea what the red stuff in 2 of those slots are, I assume it's there to help seat the tubes

This is the only one that looks a little weird to me. The third fuse down is completely white, i'm guessing it's blown? Any idea as to why it might be blown?

 

[MarcusGHedwig]

Change the main (back) fuse anyway, the same thing happened to my old JSX, and even though the fuse looked fine I replaced it (a pack of 3 is like $4 at Radio Shack) and that fixed the problem

 

[AntonioPetrole]

Change the main (back) fuse anyway, the same thing happened to my old JSX, and even though the fuse looked fine I replaced it (a pack of 3 is like $4 at Radio Shack) and that fixed the problem

and that would be the one in the first picture? Sorry, I just don't know anything about this stuff! I'm sure as hell learning alot right now though lol.

 

[colonel kurtz]

that 3rd fuse may not necessarily be faulty...sometimes they're just made with the window being covered on the inside like that, but that's something that's more common in a slow-blow fuse, which is definitely not what you want in any kind of electronics.

really the best thing you can get for checking fuses is a simple continuity tester...get one at whatever hardware/home improvement place is most convenient. they're only like 5 bucks, and you just touch each lead to one end of the fuse, and if it lights up the fuse is good...no light and it's done for.

 

[AntonioPetrole]

that 3rd fuse may not necessarily be faulty...sometimes they're just made with the window being covered on the inside like that, but that's something that's more common in a slow-blow fuse, which is definitely not what you want in any kind of electronics.

really the best thing you can get for checking fuses is a simple continuity tester...get one at whatever hardware/home improvement place is most convenient. they're only like 5 bucks, and you just touch each lead to one end of the fuse, and if it lights up the fuse is good...no light and it's done for.

Great, I'll go out and grab one when I go food shopping tonight. Any chance of getting shocked when I take out the fuse if it's unplugged? Do I have to take out the fuse?

Cheers!

 

[colonel kurtz]

if it's unplugged then no, no chance of shock

and you don't need to take it out to test it, since both ends of the fuse are easily accessible in the holders

 

[psycle_1]

From the looks of the picture, it looks like the fuse on the bottom is blown (dark spot in the middle towards the bottom of the fuse). This is a 2 amp fast acting fuse, and if it blows, you will lose high voltage to all the tubes. The standby LED gets power from this circuit as well, which would explain why it is not lighting up. Check this fuse first.

 

[psycle_1]

that 3rd fuse may not necessarily be faulty...sometimes they're just made with the window being covered on the inside like that, but that's something that's more common in a slow-blow fuse, which is definitely not what you want in any kind of electronics.

Some amp makers, such as Mesa use slo-blow fuses as their main fuse. Reason being, the large rush of current once you take an amp off of standby will kill a fast acting fuse in an instant. I tried to substitute a fast acting fuse in my Mesa power amp and it popped immediately after flipping the standby switch.

 

[MarcusGHedwig]

and that would be the one in the first picture? Sorry, I just don't know anything about this stuff! I'm sure as hell learning alot right now though lol.

Yup, that one, and you absolutely want a glass slow-blow for the main fuse on any tube amp (according to the manuals for multiple manufacturers) - take a look at the writing on the metal ends, I'm guessing 2A 250V, maybe 3A, Radio Shack, done

Also, the 3rd fuse from the top out of those 4 is indeed perfectly fine, it's a ceramic fuse

 

[AntonioPetrole]

Yup, that one, and you absolutely want a glass slow-blow for the main fuse on any tube amp (according to the manuals for multiple manufacturers) - take a look at the writing on the metal ends, I'm guessing 2A 250V, maybe 3A, Radio Shack, done

Also, the 3rd fuse from the top out of those 4 is indeed perfectly fine, it's a ceramic fuse

Some amp makers, such as Mesa use slo-blow fuses as their main fuse. Reason being, the large rush of current once you take an amp off of standby will kill a fast acting fuse in an instant. I tried to substitute a fast acting fuse in my Mesa power amp and it popped immediately after flipping the standby switch.

From the looks of the picture, it looks like the fuse on the bottom is blown (dark spot in the middle towards the bottom of the fuse). This is a 2 amp fast acting fuse, and if it blows, you will lose high voltage to all the tubes. The standby LED gets power from this circuit as well, which would explain why it is not lighting up. Check this fuse first.

if it's unplugged then no, no chance of shock

and you don't need to take it out to test it, since both ends of the fuse are easily accessible in the holders

You guys are seriously the best. I haven't had time to check the fuses with the continuity tester but I bet it's that bottom fuse, if not also possibly the main one.

So my question is, what might have caused it to blow? Maybe it has something to do with why my amp sounds like shit if I don't warm up it for a long time? Or maybe the fuse has been somewhat blown for a while and this was the final straw. Hmmmm. I'm waking up super early tomorrow to go buy one of those testers and see what I can do, I have to reamp tomorrow night so lets keep our fingers crossed.

Thanks again to all of you who have posted in here <3 I'll give you all an update tomorrow morning.

Cheers!

 

[psycle_1]

One of the power tubes internally shorted out, which will cause it will blow the fuse. How old are the power tubes? If you have to wait 10 minutes before going off standby in order to play without noises coming from the amp, I'd be willing to bet the tubes were on their last leg and this last time was their finale. LOL.

 

[psycle_1]

Also, your main fuse is most likely fine. Otherwise, the amp wouldn't power up at all.

 

[AntonioPetrole]

One of the power tubes internally shorted out, which will cause it will blow the fuse. How old are the power tubes? If you have to wait 10 minutes before going off standby in order to play without noises coming from the amp, I'd be willing to bet the tubes were on their last leg and this last time was their finale. LOL.

That's interesting. The tubes were all changed about 4 months ago. I only use the amp maybe 3 days a week at most. There were 1 or 2 nights were I accidentally left it on standby all night but I turned it off the proceeding mornings. They look brand new too, perhaps maybe one is seated incorrectly.

 

[psycle_1]

Get some contact cleaner, spray it on the pins of the tubes, and insert and remove the tube from the socket multiple times. Wait about an hour or so before turning on the amp to give the cleaner time to evaporate.