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fkalich
post Nov 25 2008, 12:36 PM
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Someone a few weeks ago mentioned this site. It really will answer your tube amp questions. I have had a Carvin 50 Bel Air tube amp sitting for 6 months after blowing a fuse, but now I have diagnosed the problem (using the page at the site)

https://ssl.eurotubes.com/euro-i.htm?page=faq#2.

And I will not even think of taking my amp to a tech to replace tubes, there is absolutely no need, you can do this kind of thing yourself (determine your problems are tube related, and then take care of replacement and biasing yourself.) Provided you are not mentally deficient, drunk, or both.

The key is watching your tubes. You can tell which is bad by testing as he said....

1) Take out the power tubes. Turn on the amp. If it does not blow a fuse, you problem is probably tube related.
2) Turn off the amp. Put the 1st tube in (make sure you kept them in order when you took them out). Turn on the amp, and watch the tubes. If the metal plate starts to heat up and glow, turn it off, you found a bad tube. Or if the blue lights in the middle of the tube don't turn on.
3) If the first tube was fine (you can actually play your guitar with only 1 of the 4 installed...at least I could), then turn off the amp, put the second tube in, and watch the tubes for 5 minutes.

You can tell bad tubes by how they look when turned on. And when one goes bad, it will cause the others to go bad (or blow a fuse).

In my case I had one that was clearly bad. It looked like the others at standby, but when I turned on the amp (out of standby) the blue lights in the middle of that tube did not come on. Then I would see other tubes with the metal plating starting to glow orange (you immediately turn off the amp when you see this...you don't want to blow the transformer). After substituting for the bad tube, I found I had a second tube that still functions, but it clearly is about to blow, other tube's plating would start to glow after a few minutes. That should not happen. It also looked different at standby, the light at the top was brighter than on the others. Just watch for inconsistencies to help you diagnose the problem.

Anyway, I now know that my amp is fine, just needs a new set of tubes. I think what happened was tube 4 shorted out, and this effected tube 3 before the fuse blew, and so tube 3 would do the same thing if I used it. Anyway, the site is great, thanks for whoever mentioned it, you learn a lot from the forum. Just be sure to read all he writes. For example, you need to clean your sockets, he says that is important.

This post has been edited by fkalich: Nov 25 2008, 12:56 PM
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OrganisedConfusi...
post Nov 25 2008, 12:54 PM
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I really need to check my tubes as I think I need to change them desperately. Although I'm selling my JCM 800 currently. It's just too big an amp for what I need.


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fkalich
post Nov 25 2008, 01:04 PM
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QUOTE (OrganisedConfusion @ Nov 25 2008, 06:54 AM) *
I really need to check my tubes as I think I need to change them desperately. Although I'm selling my JCM 800 currently. It's just too big an amp for what I need.



Besides tube 4 that was obviously bad (it did not even light up in the middle when taken out of standby like the others), tube 3 was about to go bad. It looked a little different. The light at the top was brighter than on the other two apparantly good tubes. And then I saw the plating on one of those start to turn red hot. I replaced tube 3 with a spare, and it looked normal, and the plating on the other tube did not go red hot. That is what you watch for. And you turn it off if that starts to happen. It takes a bit of time, you can see it start to happen and shut if off before anything blows. I think the key is just looking at them. If one or another does not look the same, something is probably going to go wrong. The flat curved metal plating in the tube starts to glow red, turn it off, that should not happen. It might not be that tube being bad, I could see that it was cause by another tube being bad. That is pretty much why you change a set, if one goes bad, it probably did some damage to others, even if they were pretty new.

He has videos describing how to bias, and sells a probe for $25, and a meter for $10. And that is all you need. Also he describe how to customize your bias for special sounds, he discusses that in depth. I will definitely buy from the guy.

This post has been edited by fkalich: Nov 25 2008, 01:07 PM
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OrganisedConfusi...
post Nov 25 2008, 01:08 PM
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I know how to bias an amp. I am an electronics engineer lol. I'd be a bit hopeless if I couldn't. I know 2 of the tubes have gone as they don't do anything biggrin.gif


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fkalich
post Nov 25 2008, 01:10 PM
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QUOTE (OrganisedConfusion @ Nov 25 2008, 07:08 AM) *
I know how to bias an amp. I am an electronics engineer lol. I'd be a bit hopeless if I couldn't. I know 2 of the tubes have gone as they don't do anything biggrin.gif


As I understand it, the two inside are mated, and the two outside. They share the same power source. Mates tend to go bad together.

Does it damage an amp to run it with only part of the tubes? My amp played with just one power tube installed. I was wondering, just curious.

This post has been edited by fkalich: Nov 25 2008, 01:11 PM
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OrganisedConfusi...
post Nov 25 2008, 01:13 PM
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QUOTE (fkalich @ Nov 25 2008, 12:10 PM) *
As I understand it, the two inside are mated, and the two outside. They share the same power source. Mates tend to go bad together.

Does it damage an amp to run it with only part of the tubes? My amp played with just one power tube installed. I was wondering, just curious.

Nope. You can take tubes out to make the amp less powerful.

Again it's far from easy to damage tube amps. They are made a lot better than modern digital amps. I've blown up 6 digital amps in my playing life and I still have a 28 year old JCM 800 in working order smile.gif

This post has been edited by OrganisedConfusion: Nov 25 2008, 01:14 PM


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Ivan Milenkovic
post Nov 25 2008, 02:08 PM
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Some amps don't allow it, but some good quality amps can run even with just one tube, just like tank can run with just about any fuel smile.gif


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tommyboy
post Nov 25 2008, 02:28 PM
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QUOTE (fkalich @ Nov 25 2008, 05:36 AM) *
Someone a few weeks ago mentioned this site. It really will answer your tube amp questions.


Glad I could be of help. When I first found the site my reaction was WOW! The mother load laugh.gif

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MickeM
post Nov 25 2008, 03:13 PM
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QUOTE (fkalich @ Nov 25 2008, 01:04 PM) *
I will definitely buy from the guy.

Well invested money! Customer care, he's available for questions also after you've payed for your tubes and things.


spray some electric spray on the pins of the old tubes you're replacing, jack em in and out of the socked a couple of times before you plug the new one in. I learned that from him and it makes perfect sence, of course the sockets should be cleaned before you start using new tubes. :-)


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kjutte
post Nov 25 2008, 06:06 PM
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QUOTE (fkalich @ Nov 25 2008, 12:36 PM) *
Someone a few weeks ago mentioned this site. It really will answer your tube amp questions. I have had a Carvin 50 Bel Air tube amp sitting for 6 months after blowing a fuse, but now I have diagnosed the problem (using the page at the site)

https://ssl.eurotubes.com/euro-i.htm?page=faq#2.

And I will not even think of taking my amp to a tech to replace tubes, there is absolutely no need, you can do this kind of thing yourself (determine your problems are tube related, and then take care of replacement and biasing yourself.) Provided you are not mentally deficient, drunk, or both.

The key is watching your tubes. You can tell which is bad by testing as he said....

1) Take out the power tubes. Turn on the amp. If it does not blow a fuse, you problem is probably tube related.
2) Turn off the amp. Put the 1st tube in (make sure you kept them in order when you took them out). Turn on the amp, and watch the tubes. If the metal plate starts to heat up and glow, turn it off, you found a bad tube. Or if the blue lights in the middle of the tube don't turn on.
3) If the first tube was fine (you can actually play your guitar with only 1 of the 4 installed...at least I could), then turn off the amp, put the second tube in, and watch the tubes for 5 minutes.

You can tell bad tubes by how they look when turned on. And when one goes bad, it will cause the others to go bad (or blow a fuse).

In my case I had one that was clearly bad. It looked like the others at standby, but when I turned on the amp (out of standby) the blue lights in the middle of that tube did not come on. Then I would see other tubes with the metal plating starting to glow orange (you immediately turn off the amp when you see this...you don't want to blow the transformer). After substituting for the bad tube, I found I had a second tube that still functions, but it clearly is about to blow, other tube's plating would start to glow after a few minutes. That should not happen. It also looked different at standby, the light at the top was brighter than on the others. Just watch for inconsistencies to help you diagnose the problem.

Anyway, I now know that my amp is fine, just needs a new set of tubes. I think what happened was tube 4 shorted out, and this effected tube 3 before the fuse blew, and so tube 3 would do the same thing if I used it. Anyway, the site is great, thanks for whoever mentioned it, you learn a lot from the forum. Just be sure to read all he writes. For example, you need to clean your sockets, he says that is important.


Thanks! I needed this.
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fkalich
post Nov 26 2008, 04:32 PM
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QUOTE (kjutte @ Nov 25 2008, 12:06 PM) *
Thanks! I needed this.


You are welcome.

To all, I got a reply from Eurotubes regarding running an amp without all its tubes in (my Carvin Bel Air will run with only 1 of the 4 tubes. This is what they told me.

"While some amps depending on the design of their power section, may function with just three or even one single power tube installed, they will not be operating efficiently. In many cases, this practice can very quickly damage the tubes, the transformer, or both"

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Noangels
post Nov 27 2008, 09:33 AM
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Cool info thanks:)The bel air is a great little and powerfull amp!The only downside it has is its fuzzy overdrive when driven hard.Not nice at all-I used to play it with gain just over half way

but messing around with the amp at rehearsals(never use it,its just sat there!)I found that wacking the gain to full and adding a lot of bass while rolling back treble with some fine tuning on the mid it gave an amazing lead tone that realy sounded like Vinnie moores tone on his 1st couple of albums.Myself and the other guitarist couldnt stop playing lines over it and we plan to record some band solos on it just to see how it fits in the mix


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Muris Varajic
post Nov 27 2008, 01:28 PM
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Bob is awesome guy,I bought several tube kits from them
and got answers for every single question I asked,highly recommended. smile.gif


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