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Post subject: Adjustable Bias for Blues Junior III....
Posted: Sat Oct 01, 2011 12:26 pm
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I'm having some issues with the output tubes on my blues jr III. One of them lights up like it's gonna blow up, and then I lose all base and tone. I've been reading around about mods, and I read somewhere that the stock fixed bias on the blues jr. is way too hot, and that it cooks output tubes pretty darn quick. Is that my problem? (btw, I've only had the amp 4 1/2 months, gets played and gigged with a lot.) If so, where's the best place to get this mod done? :?: HELP!

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Last edited by Telemonster4 on Sun Oct 02, 2011 2:53 pm, edited 1 time in total.

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Sat Oct 01, 2011 12:37 pm
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If you've only had the amp for 4.5 months, leave it alone and take it to an authorized Fender repair center and have it checked out under warranty. If you mod the amp, it will void the warranty.

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Sat Oct 01, 2011 12:44 pm
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bluesky636 wrote:
If you've only had the amp for 4.5 months, leave it alone and take it to an authorized Fender repair center and have it checked out under warranty. If you mod the amp, it will void the warranty.



This is my first tube amp, so forgive me if I sound stupid, but are tubes under Fender's warranty?

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Sat Oct 01, 2011 7:35 pm
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Hi Telemonster4,

I believe that it is 90 days for tubes in a new Fender amp.

http://support.fender.com/warranty/FENDER_5-YEAR_ELECTRONIC_PRODUCTS_WARRANTY_9-2001.pdf

You might just have a bad tube, and a new matched set will probably be all that you need for now. Although the tubes do run very hot in the BJr, and the amp can benefit from an adjustable bias, if the bias was causing the issue, it would likely be both tubes with a problem. It is possible that you have an amp problem, but since the original tubes might be past their warranty, try a new set, and if you still have the same issue, the rest of the amp should be covered so you could then get warranty repair before the new tubes are damaged. Odds are good that it is only a tube issue.

As mentioned, modifying "no matter how slight" will void warranty. If you understand the risk and want to add an adjustable bias, check the Billm site for kits. I have added an adjustable bias to my BJr after owning it for a couple of years, and I think that it is now past the five year warranty period, but still going strong.

http://billmaudio.com/wp/

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Last edited by shimmilou on Sat Oct 01, 2011 7:48 pm, edited 1 time in total.

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Sat Oct 01, 2011 7:36 pm
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A warranty card came with your amp. You should have read it. Since you obviously haven't, here it is:

http://support.fender.com/warranty/FEND ... 9-2001.pdf

To answer your question, tubes are warranteed for 90 days, but if there is a problem with the amp, such as the bias being set improperly due to a component failure which then causes the tubes to fail, that problem is covered. Modding the amp by adding a bias adjustment pot (which are readily available) will definitely void the warranty. Some people may not care, but since this is your first tube amp (and I sense that you don't really know that much about tube amps) I suggest you take the amp to an authorized amp technician.

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Sat Oct 01, 2011 7:54 pm
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Here's what it takes to add an adjustable bias to a Pro Junior/Blues Junior. Component designations may be different on a BJ III and a schematic would have to be located. This is not something a novice should attempt even if the warranty is to be ignored.

http://billmaudio.com/wp/?page_id=916

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Sun Oct 02, 2011 2:07 pm
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bluesky636 wrote:
Here's what it takes to add an adjustable bias to a Pro Junior/Blues Junior. Component designations may be different on a BJ III and a schematic would have to be located. This is not something a novice should attempt even if the warranty is to be ignored.

http://billmaudio.com/wp/?page_id=916



I have already looked at all of the billm mods, and no I would'nt do it myself (You're right, I am a novice when it comes to tube amps). I bought my amp brand new from a local guitar shop, and it didn't come with the tags (which I found from a friend that it comes with a five year warranty), thats why I asked.

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Sun Oct 02, 2011 2:11 pm
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shimmilou wrote:
Hi Telemonster4,

I believe that it is 90 days for tubes in a new Fender amp.

http://support.fender.com/warranty/FENDER_5-YEAR_ELECTRONIC_PRODUCTS_WARRANTY_9-2001.pdf

You might just have a bad tube, and a new matched set will probably be all that you need for now. Although the tubes do run very hot in the BJr, and the amp can benefit from an adjustable bias, if the bias was causing the issue, it would likely be both tubes with a problem. It is possible that you have an amp problem, but since the original tubes might be past their warranty, try a new set, and if you still have the same issue, the rest of the amp should be covered so you could then get warranty repair before the new tubes are damaged. Odds are good that it is only a tube issue.

As mentioned, modifying "no matter how slight" will void warranty. If you understand the risk and want to add an adjustable bias, check the Billm site for kits. I have added an adjustable bias to my BJr after owning it for a couple of years, and I think that it is now past the five year warranty period, but still going strong.

http://billmaudio.com/wp/




Thanks shimmilou, I think this is the route that I'm gonna go with (New tubes). It's been past 90 days so I'll order a new pair. Would you recommend the same groove tubes? (It came with the EL-84 7's I believe) If I get a lower number will my tubes last longer? (Like a 6 maybe?)

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Sun Oct 02, 2011 2:15 pm
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Telemonster4 wrote:
bluesky636 wrote:
Here's what it takes to add an adjustable bias to a Pro Junior/Blues Junior. Component designations may be different on a BJ III and a schematic would have to be located. This is not something a novice should attempt even if the warranty is to be ignored.

http://billmaudio.com/wp/?page_id=916



I have already looked at all of the billm mods, and no I would'nt do it myself (You're right, I am a novice when it comes to tube amps). I bought my amp brand new from a local guitar shop, and it didn't come with the tags (which I found from a friend that it comes with a five year warranty), thats why I asked.


Ok. So take the amp to an authorized service center to have it checked out under warranty to see if anything is wrong. If so, get it fixed, then decide if you really want to mod the amp and void the warranty. A Fender authorized service center may not be willing to mod the amp for you.

http://www.fender.com/support/articles/ ... dification

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Sun Oct 02, 2011 2:25 pm
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Ok. So take the amp to an authorized service center to have it checked out under warranty to see if anything is wrong. If so, get it fixed, then decide if you really want to mod the amp and void the warranty. A Fender authorized service center may not be willing to mod the amp for you.


Thanks bluesky636, I'm going to take it in, the only reason I would mod it is if it happens again, so I'm not going to do it right away.

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Sun Oct 02, 2011 4:30 pm
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Yes, I would recommend GTs. The number and color rating has nothing to do with tube life, the rating has to do with breakup point (distortion). Blue 1 to 3 is for early breakup, White 4 to 7 is mid range, and Red 8 to 10 is for clean headroom. I prefer the red for clean output section, and I get my distortion from the preamp or pedals. I suspect that your amp came stock with white labels. The labels may not actually be those colors, but the newer labels just say "Blue" or "White" or "Red", with a number.

If you like the sound that you have now, stick with the same color/number rating. If you want earlier breakup use blue, if you want cleaner use red.

Check to be sure that there isn't a fee for diagnosing the amp problem, you may very well get charged if there is no issue with the amp, many places do this. I'm sure that they can determine that the tube is bad, then charge you a diagnostic fee, and/or a fee for checking/changing the tubes. This is why I suggest just changing the tubes yourself, but you may be OK with paying for the check-up and new tubes installed. I guess that I'm more of a DIY guy and have never taken any of my gear to a shop, although I might if I ever have a warranty issue, haven't so far. :idea:

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Mon Oct 03, 2011 7:27 am
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shimmilou wrote:
Yes, I would recommend GTs. The number and color rating has nothing to do with tube life, the rating has to do with breakup point (distortion). Blue 1 to 3 is for early breakup, White 4 to 7 is mid range, and Red 8 to 10 is for clean headroom. I prefer the red for clean output section, and I get my distortion from the preamp or pedals. I suspect that your amp came stock with white labels. The labels may not actually be those colors, but the newer labels just say "Blue" or "White" or "Red", with a number.

If you like the sound that you have now, stick with the same color/number rating. If you want earlier breakup use blue, if you want cleaner use red.

Check to be sure that there isn't a fee for diagnosing the amp problem, you may very well get charged if there is no issue with the amp, many places do this. I'm sure that they can determine that the tube is bad, then charge you a diagnostic fee, and/or a fee for checking/changing the tubes. This is why I suggest just changing the tubes yourself, but you may be OK with paying for the check-up and new tubes installed. I guess that I'm more of a DIY guy and have never taken any of my gear to a shop, although I might if I ever have a warranty issue, haven't so far. :idea:




Thanks, this is exactly the info I'm looking for, my blues junior came stock with the Groove Tube Gold Series El-84 R matched power tubes (mine were the 7's), and I'm going to order a new set, should i go with a bigger number (I like clean headroom and I use pedals exstensivly)? Should I get the 8-10 set? (I need my amp running by thursday.... :? )

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Mon Oct 03, 2011 8:14 am
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Yes, red 8 to 10 are great for the most clean headroom. Further, while the -R is a decent, very rugged tube, and great if you use pedals all the time, the -S are a bit richer musically IMO. Check out the "GT EL84-S" red label that I use in my BJr. For $35 a matched pair, they're hard to beat.

http://www.guitarcenter.com/Groove-Tubes-Gold-Series-GT-EL84-S-Matched-Power-Tubes-219169-i1125772.gc?esid=GT+EL84+S

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Mon Oct 03, 2011 2:29 pm
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shimmilou wrote:
Yes, red 8 to 10 are great for the most clean headroom. Further, while the -R is a decent, very rugged tube, and great if you use pedals all the time, the -S are a bit richer musically IMO. Check out the "GT EL84-S" red label that I use in my BJr. For $35 a matched pair, they're hard to beat.



Whats the difference between the -R and -S? (other than sounding better..) No re-biasing, right? (If not, I'm gonna try the -S tubes)

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Post subject: Re: Adjustable Bias for Blues Junior III....
Posted: Mon Oct 03, 2011 4:31 pm
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Basically the ending letter designates where the tubes are made. R is Russia, S is Slovakia (made in the JJ factory, NOT the same as JJ tubes), C is Chinese, etc. Each has a different design/specs, and different sound. The S are able to handle higher Plate voltages and more power than the R or C (the S would better handle the hot bias in the BJr). There is no bias adjust on the stock BJr, and many many people just put in new tubes and go. Some brands that I know of being used without bias adjust, are GT (R and S), JJ, EH, Telefunkin, TAD, and many more. My preference was to add a bias adjust (yes, my warranty is void). :idea:

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