#1
My friend who I made a thread for earlier last month finally got a JCM 800 2205. He took his amp to a tech to get some new tubes biased and the amp checked over.

He was playing on his amp just now, at about 4 or 5 on the master volume, and it just cut off. He gave it a second to turn cool off, and then he turned it back on, and it turned back on. He told me that both his tubes were working and it sounds normal.

What could it be?
GEAR
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#3
don't **** with expensive things don't ask dumb a$$e$ here go 2 a guitar shop ask an expert that u don't no wat ur doing neither does anyone here trust take it 2 a shop
#4
Quote by RaiderFootball1
don't **** with expensive things don't ask dumb a$$e$ here go 2 a guitar shop ask an expert that u don't no wat ur doing neither does anyone here trust take it 2 a shop

....yeah, thanks.
GEAR
Epiphone SG-400
Marshall 1987 JCM-800 2210 100W

Proud Member of:
The SG Owners Unite
Marshall Amplification
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#5
Don't touch anything. The people on this forum may be able to tell you what amps and pedals and guitar are good and bad, but i wouldn't trust anyone to diagnose a problem like that for you. Take it to a tech and have it looked at by a professional.
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#6
Quote by RaiderFootball1
don't **** with expensive things don't ask dumb a$$e$ here go 2 a guitar shop ask an expert that u don't no wat ur doing neither does anyone here trust take it 2 a shop


can u r b fixen ur gramars plz?

btw, sigged lul
Quote by Aurex
Knightmare you are the winner


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Last edited by Knightmare444 at Jul 10, 2009,
#8
Any other comments?
GEAR
Epiphone SG-400
Marshall 1987 JCM-800 2210 100W

Proud Member of:
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#9
Quote by Weeping_Demon7
My friend who I made a thread for earlier last month finally got a JCM 800 2205. He took his amp to a tech to get some new tubes biased and the amp checked over.

He was playing on his amp just now, at about 4 or 5 on the master volume, and it just cut off. He gave it a second to turn cool off, and then he turned it back on, and it turned back on. He told me that both his tubes were working and it sounds normal.

What could it be?

Check the OT fuse. If it's blown, replace it and start checking to make sure the power tubes are all properly socketed.
Everyone is entitled to an opinion.

Feel free to express yours so I can make an informed judgement about how stupid you are.
#10
Quote by bubb_tubbs
Check the OT fuse. If it's blown, replace it and start checking to make sure the power tubes are all properly socketed.

How will I know that the fuse is blown?
GEAR
Epiphone SG-400
Marshall 1987 JCM-800 2210 100W

Proud Member of:
The SG Owners Unite
Marshall Amplification
EHX Users Guild

The True Eccentric Tea Drinking Appreciation Preservation Society

#11
Quote by Weeping_Demon7
How will I know that the fuse is blown?

http://media.photobucket.com/image/marshall%20fuse/mikey383/0212090904.jpg

The metal inside will still be intact if the fuse is functional.

If it's blown, some or all of it will have sublimated during the power surge.
Everyone is entitled to an opinion.

Feel free to express yours so I can make an informed judgement about how stupid you are.
#12
One thing that all amp owners should own is a multimeter it will be your best friend! But if you don't have one having an electrician as your best friend is just as good
#13
Quote by AxSilentxLine
One thing that all amp owners should own is a multimeter it will be your best friend! But if you don't have one having an electrician as your best friend is just as good

I wish my school had an electronics class. Alas.
GEAR
Epiphone SG-400
Marshall 1987 JCM-800 2210 100W

Proud Member of:
The SG Owners Unite
Marshall Amplification
EHX Users Guild

The True Eccentric Tea Drinking Appreciation Preservation Society

#14
Quote by Weeping_Demon7
I wish my school had an electronics class. Alas.

If I lived near you, I could check it out.

(Electrician)
Everyone is entitled to an opinion.

Feel free to express yours so I can make an informed judgement about how stupid you are.
#15
Quote by bubb_tubbs
If I lived near you, I could check it out.

(Electrician)

It's so damned important to any guitarist to be able to fix their equipment. But these days, most people don't even know what the hell a vacuum tube is; so most of the knowledge that the amp techs of today have is passed down from 20 or 30 years ago.

I would kill to be able to be completely understand every component of my guitar and amp (although I think I understand the guitar electrics pretty well). But tube amps are like an art.
GEAR
Epiphone SG-400
Marshall 1987 JCM-800 2210 100W

Proud Member of:
The SG Owners Unite
Marshall Amplification
EHX Users Guild

The True Eccentric Tea Drinking Appreciation Preservation Society

#16
Fuses are either blown or they're not. If blown, the amp won't work. If not, it works if everything else is OK. An intermittently functioning amp does not have a blown fuse. corroded connections? - Maybe, but unlikely.

I would continue to play it and see if it repeats the problem. If not, don't worry. If it does it again, take it in to a tech. All the electronics test equipment in the world won't do a thing for you if you don't know what you're looking for. Don't go poking inside a tube amp unless you know EXACTLY what you're doing.
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#17
Quote by Vulcan
Fuses are either blown or they're not. If blown, the amp won't work. If not, it works if everything else is OK. An intermittently functioning amp does not have a blown fuse. corroded connections? - Maybe, but unlikely.

I would continue to play it and see if it repeats the problem. If not, don't worry. If it does it again, take it in to a tech. All the electronics test equipment in the world won't do a thing for you if you don't know what you're looking for. Don't go poking inside a tube amp unless you know EXACTLY what you're doing.


It's called a schematic and fyi it's actually pretty darn easy to test a power circuit you start from the end and work back. If it doesn't turn on there's pretty good chance that it's a fuse but you can easily test it
#18
a schematic doesn't tell you how to drain filter caps, and not everyone can easily translate a schematic into the amp layout so as to know where the danger areas in the amp are.

As for a fuse, just pull it out and look at it, if it's blown, you can SEE that it's blown quite easily, just replace it and keep going if it keeps blowing then you've got a problem. But Vulcan is right, if the amp continues to function it's not a fuse problem, neither mains fuse or ht fuse.
#19
Quote by AxSilentxLine
It's called a schematic and fyi it's actually pretty darn easy to test a power circuit you start from the end and work back. If it doesn't turn on there's pretty good chance that it's a fuse but you can easily test it



If the guy doesn't know how to check a blown fuse, I am confident that the best schematic in the world, the most expensive multimeter, and a vintage oscilloscope pulled out of NASA's own lab will not help him.

To the OP, I couldn't tell from the original post, did it start working again? If that is the case, it is not a fuse. If the Amp is still working fine, I would keep playing it, if it stops again, take it to a tech, if you are new enough to the whole game that you don't know how to check a fuse, do yourself and the amp a favor and get it to a tech. If it is a cool tech, maybe he'll show you a bit of the basics (like checking a fuse and making sure the tubes are seated correctly) and you can start down the path of being a tube amp guru.
#21
Quote by Fetus Milkshake
Il bet anything its the amps fuse!


A fuse is a one shot deal.

Here's the deal. Explain to me how the amp stops working and then starts again if the fuse is blown? Then stop giving answers to things you don't understand.
#22
Quote by bubb_tubbs
Check the OT fuse. If it's blown, replace it and start checking to make sure the power tubes are all properly socketed.


Again. How can the amp start working again if as you suggest the FUSE IS BLOWN?

You too can stop posting answers to things you don't understand.
#23
I'm going for dodgy input jack connection or loop connectors (I can't remember if the JCM has a loop :/ )
...
#24
Welcome to the world of tube amps, it might be fine if it still works keep playing it. They can be temperamental but they can always be fixed. All you can do is make sure all the tubes are seated properly and no plugs or jacks are wiggled loose etc.
#25
Quote by Vulcan
Fuses are either blown or they're not. If blown, the amp won't work. If not, it works if everything else is OK. An intermittently functioning amp does not have a blown fuse. corroded connections? - Maybe, but unlikely.

I would continue to play it and see if it repeats the problem. If not, don't worry. If it does it again, take it in to a tech. All the electronics test equipment in the world won't do a thing for you if you don't know what you're looking for. Don't go poking inside a tube amp unless you know EXACTLY what you're doing.

That was my bad - I missed the part where he said the amp fired up again after and was under the impression that it had just abruptly died during playing.
Quote by BobDetroit
Again. How can the amp start working again if as you suggest the FUSE IS BLOWN?

You too can stop posting answers to things you don't understand.

You're a ****ing idiot. If you check my profile or read the rest of the thread and see I'm an electrician, I obviously know that a blown overcurrent fuse will open the circuit and make it unusable.

I simply missed the part at the end where he said the amp functioned again. Perhaps you should read more before knee-jerking people who are trying to help.
Everyone is entitled to an opinion.

Feel free to express yours so I can make an informed judgement about how stupid you are.
Last edited by bubb_tubbs at Jul 11, 2009,
#26
Quote by bubb_tubbs
You're a ****ing idiot. If you check my profile or read the rest of the thread and see I'm an electrician, I obviously know that a blown overcurrent fuse will open the circuit and make it unusable.

I simply missed the part at the end where he said the amp functioned again. Perhaps you should read more before knee-jerking people who are trying to help.


You're making a personal attack on me because while you didn't actually read the original post, I omitted researching your profile to discover you're an "electrician" and despite your blatantly incorrect answer failed to assume you really do know what you're talking about.. ..?..???

apologies to the TS.
#27
Quote by Knightmare444
Don't touch anything. The people on this forum may be able to tell you what amps and pedals and guitar are good and bad, but i wouldn't trust anyone to diagnose a problem like that for you. Take it to a tech and have it looked at by a professional.


I would trust guys on here like IbanezPsycho more than I would 90% of people who say they work on amps at guitar shops.

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#28
Quote by BobDetroit
You're making a personal attack on me because while you didn't actually read the original post, I omitted researching your profile to discover you're an "electrician" and despite your blatantly incorrect answer failed to assume you really do know what you're talking about.. ..?..???

Illogical though it may seem to you, that's precisely my position.
Everyone is entitled to an opinion.

Feel free to express yours so I can make an informed judgement about how stupid you are.
#29
Quote by Necrophagist777
I would trust guys on here like IbanezPsycho more than I would 90% of people who say they work on amps at guitar shops.
That's why you bring it an amp tech, not a guitar shop.
#30
Quote by al112987
That's why you bring it an amp tech, not a guitar shop.


I understand, he is an amp tech I was just responding to that guy's statement that no one on UG knows what they are talking about.

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Last edited by Necrophagist777 at Jul 11, 2009,
#31
well no, it's not that, its just that there are certain problems that can't really be diagnosed unless you actually have the amp sitting there in front of you that you can look at. The problem he has is very peculiar, which is why the other guy probably suggested that no one here could really give that much advice.
#32
Quote by bubb_tubbs
That was my bad - I missed the part where he said the amp fired up again after and was under the impression that it had just abruptly died during playing.


No problem.

I think more than a couple of posters didn't read the whole post thoroughly before replying. Some of the posters need to realize though that myself and a few others here wouldn't counsel anyone who doesn't know how to check a fuse to start working through a tube amp circuit. Mistakes are potentially fatal, and someone who doesn't know how to check a fuse or isn't sure what the symptoms suggesting a blown fuse are (or in this case aren't) has no business with an amp opened up in front of them.

I work daily with equipment from 600V up to 230kV and have a really healthy respect for electricity, one I'm certain you have too, being an electrician. Ever see a 230kV breaker closed while maintenance grounds are still attached to the load side? I have. Blowed up real good.
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#33
Quote by al112987
well no, it's not that, its just that there are certain problems that can't really be diagnosed unless you actually have the amp sitting there in front of you that you can look at. The problem he has is very peculiar, which is why the other guy probably suggested that no one here could really give that much advice.


Very true. But I don't think that's what the guy who got banned and couldn't forge a complete sentence was talking about.

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#34
If the fuse was blown, the amp wouldn't be working. I had a similar problem with my VK a while back and it turned out it was a dodgy batch of valves peavey had sent out so i got my money back and bought one from a different store.
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#35
so it simply overheated? how is it now? did it find its way to a tech? i need closure lol.
#36
Quote by Vulcan
No problem.

I think more than a couple of posters didn't read the whole post thoroughly before replying. Some of the posters need to realize though that myself and a few others here wouldn't counsel anyone who doesn't know how to check a fuse to start working through a tube amp circuit. Mistakes are potentially fatal, and someone who doesn't know how to check a fuse or isn't sure what the symptoms suggesting a blown fuse are (or in this case aren't) has no business with an amp opened up in front of them.

I work daily with equipment from 600V up to 230kV and have a really healthy respect for electricity, one I'm certain you have too, being an electrician. Ever see a 230kV breaker closed while maintenance grounds are still attached to the load side? I have. Blowed up real good.

Eating 300V DC is always a good time.

It was only across my index and ring fingers but it ached for days.

Somebody had left a connection floating inside a motor disconnect and it was live even with the mains off.
Everyone is entitled to an opinion.

Feel free to express yours so I can make an informed judgement about how stupid you are.
Last edited by bubb_tubbs at Jul 12, 2009,