#1
So I've had a Fender BJ for about over two years and I've played it a decent amount on my own, at band practices. Lately I've been getting some odd sounds from it so I did the pencil test on the tubes (you know, plug the guitar in, turn the guitar's volume down and the amp's up, then tap them with the eraser of the pencil). All the tubes sound fine but when I get to the far right preamp tube I hear a loud "ch"/popping sound. Is this a sign that it's time to change the tube(s) in it? It's my first tube amp and so I'm not sure what to look for. Also, would I have to change all or just the one? Thanks!
Squier Strat => Fulltone OCD => MXR Phase 90 => Boss DD-3 => Fender Blues Jr.
#2
Quote by grazzi
So I've had a Fender BJ for about over two years and I've played it a decent amount on my own, at band practices. Lately I've been getting some odd sounds from it so I did the pencil test on the tubes (you know, plug the guitar in, turn the guitar's volume down and the amp's up, then tap them with the eraser of the pencil). All the tubes sound fine but when I get to the far right preamp tube I hear a loud "ch"/popping sound. Is this a sign that it's time to change the tube(s) in it? It's my first tube amp and so I'm not sure what to look for. Also, would I have to change all or just the one? Thanks!


if the sound you were describing was while tapping the tube, then yes, that is a microphonic tube.

i just wanted to clarify if it was while tapping, it didn't read the clearest to me (no big deal).

i hate tubes relating to fender tube amps, i have heard something odd about tube selection of them, but unfortunately i can not recall.
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#3
Quote by trashedlostfdup
if the sound you were describing was while tapping the tube, then yes, that is a microphonic tube.

i just wanted to clarify if it was while tapping, it didn't read the clearest to me (no big deal).

i hate tubes relating to fender tube amps, i have heard something odd about tube selection of them, but unfortunately i can not recall.


Yeah the sound happens when I tap it. I also get a strange sound sometimes when I play, like I'll hit a note and I get a fzzzzzzz after it... Hm.
Squier Strat => Fulltone OCD => MXR Phase 90 => Boss DD-3 => Fender Blues Jr.
#4
You are talking about the preamp valve furthest from the input jack, yes? The phase inverter? Those are normally the first to go (well, unless you have a Sovtek in the tone stack). Just replace that one tube and see how you go. I recommend a JJ in that position or, better still if you can afford it grab a JAN Phillips. You will want a balanced one.
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#5
Quote by Cathbard
You are talking about the preamp valve furthest from the input jack, yes? The phase inverter? Those are normally the first to go (well, unless you have a Sovtek in the tone stack). Just replace that one tube and see how you go. I recommend a JJ in that position or, better still if you can afford it grab a JAN Phillips. You will want a balanced one.


No it's actually the one right under the input jack. I've got the version before the BJ III came out, if that changes anything.
Squier Strat => Fulltone OCD => MXR Phase 90 => Boss DD-3 => Fender Blues Jr.
#6
Ah, so it's V1. My recommendation remains the same except that you don't need a balanced tube. Buy two so you have a spare. If V1 has gone the others are probably not far off following it and you should always have at least one spare preamp tube.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#7
Alright I'll evaluate my economic situation and see if I can get a pair of them. Are JJ tubes any good or are there any really good ones I should look at?
Squier Strat => Fulltone OCD => MXR Phase 90 => Boss DD-3 => Fender Blues Jr.
#8
There are two main types of JJ 12AX7. There's the short plate ECC83S which is a copy of the legendary Telefunken. They also have a long plate ECC803S which is a continuation of the old Tesla low noise valve. (JJ is the old Tesla factory).
The ECC803 is a superb valve but it does have a tendency to be a bit microphonic. Not enough to be an issue in a head but in a combo like you have I'd steer clear of it and just get the ECC83S.
SED valves are good too but rather expenxive. They are made in the old Svetlana factory - not to be confused with the bogus valves actually labelled Svetlana by New Sensor (the Sovtek people)
JAN Phillips are an awesome valve and will wipe the floor with the others ^^. They are a NOS valve that can still be picked up for around $25. Well worth the extra dollars.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
Last edited by Cathbard at Aug 16, 2011,
#9
All tubes are microphonic to some degree. Just because you hear tapping through the speaker when you tapthe tubes doesn't mean it's bad. Now if you hear something else with the tapping that's a different story.
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#10
Quote by Reincaster
All tubes are microphonic to some degree. Just because you hear tapping through the speaker when you tapthe tubes doesn't mean it's bad. Now if you hear something else with the tapping that's a different story.

True but it's an easy thing to test and does give you a starting point even if it's not definitive. You just sub in your spare and see. I often use slightly microphonic old valves. I have a slightly microphonic Amperex that sounds mighty.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#11
Quote by Cathbard
True but it's an easy thing to test and does give you a starting point even if it's not definitive. You just sub in your spare and see. I often use slightly microphonic old valves. I have a slightly microphonic Amperex that sounds mighty.



true, I'm just tired of "OH THE NOEZ I tapped the tubeZ and I could hear the tapping through the speaker, are my tubez the deadness?"

Not saying this is the OP's case, but a pop and tap are sometimes the same thing. Do you see sparks or snything? Definitely get a spare and test it out.
Peavey 5150
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Mesa Single Rectifier (Series 1)
Fender Custom Shop Tonemaster
Roland Microcube

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