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Post subject: swapping out tubes
Posted: Tue Jan 21, 2014 9:09 am
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Aspiring Musician
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So after visiting tube depot I've decided upon a selection of their finest and cheapest tubes. This is more or less what came in my Blues Jr.

Anything to replacing these other than ripping the old ones out and cramming the new ones in? I know the el84s should be a matched set. What about the 12ax7s?


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Post subject: Re: swapping out tubes
Posted: Tue Jan 21, 2014 11:23 am
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Phase inverter (V3) needs to be balanced.

Normally we would tell you to check the bias on the power tubes but that can't be changed without replacing parts. Fender runs the power tubes very hot in this amp which is why many people add a bias adjustment to it. Since you can't adjust the bias on this amp, you need to buy power tubes with the same rating as the stock Groove Tubes.

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Post subject: Re: swapping out tubes
Posted: Tue Jan 21, 2014 11:30 am
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DarkPenguin,

The best EL84 type is the EL84M or Russian designation 6N14P-EV or-EB (IMHO). Be sure to buy it with the -EV or better -EB suffix. These are true mil spec tubes made to US 7189 standards. I use them in all Vox or other amps that run the EL84 in Class "A." They last.

Powerful dark tone. Growling mids. Fairly good headroom for an EL84 type.

https://tubedepot.com/products/sovtek-e ... acuum-tube

http://www.ebay.com/itm/4-Matched-NOS-S ... 256df22548


I am not associated with EBay seller. Just posted this for visual reference.


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Post subject: Re: swapping out tubes
Posted: Tue Jan 21, 2014 3:13 pm
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Aspiring Musician
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bluesky636 wrote:
Phase inverter (V3) needs to be balanced.

Normally we would tell you to check the bias on the power tubes but that can't be changed without replacing parts. Fender runs the power tubes very hot in this amp which is why many people add a bias adjustment to it. Since you can't adjust the bias on this amp, you need to buy power tubes with the same rating as the stock Groove Tubes.


By "balanced" you mean "balanced triodes" (in the tube depot parlance)?

I have 3 sovtek 12ax7wa's and 2 unidentified el84s. I was just going to stuff a pair of sovtek el84s in there.


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Post subject: Re: swapping out tubes
Posted: Tue Jan 21, 2014 3:29 pm
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DarkPenguin wrote:
bluesky636 wrote:
Phase inverter (V3) needs to be balanced.

Normally we would tell you to check the bias on the power tubes but that can't be changed without replacing parts. Fender runs the power tubes very hot in this amp which is why many people add a bias adjustment to it. Since you can't adjust the bias on this amp, you need to buy power tubes with the same rating as the stock Groove Tubes.


By "balanced" you mean "balanced triodes" (in the tube depot parlance)?

I have 3 sovtek 12ax7wa's and 2 unidentified el84s. I was just going to stuff a pair of sovtek el84s in there.


Yes.

Some people will argue that an unbalanced phase inverter is ok and that it adds a pleasant distortion to the sound. I doubt most players worried about such things "back in the day".

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Post subject: Re: swapping out tubes
Posted: Tue Jan 21, 2014 3:41 pm
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DarkPenguin wrote:
...Anything to replacing these other than ripping the old ones out and cramming the new ones in?...


In addition to the advice given, I would avoid "ripping" and "cramming". You need to be careful inserting the new tubes to avoid bending or breaking the pins on the tubes, paying particular attention to the "key" for the tubes, which is a gap in the pin lineup that must be lined up with the gap in the socket.

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Post subject: Re: swapping out tubes
Posted: Tue Jan 21, 2014 4:52 pm
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shimmilou wrote:
DarkPenguin wrote:
...Anything to replacing these other than ripping the old ones out and cramming the new ones in?...


In addition to the advice given, I would avoid "ripping" and "cramming". You need to be careful inserting the new tubes to avoid bending or breaking the pins on the tubes, paying particular attention to the "key" for the tubes, which is a gap in the pin lineup that must be lined up with the gap in the socket.



+1...Even being careful you can bend or break a pin!

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Post subject: Re: swapping out tubes
Posted: Wed Jan 22, 2014 12:29 pm
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Aspiring Musician
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I figured that out while trying to remove one of them.


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Post subject: Re: swapping out tubes
Posted: Wed Jan 22, 2014 2:04 pm
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bluesky636 wrote:
Some people will argue that an unbalanced phase inverter is ok and that it adds a pleasant distortion to the sound. I doubt most players worried about such things "back in the day".

Back in the day, you could always run down to the nearest Radio Shack and pick up a new tube or three pretty cheap.


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Post subject: Re: swapping out tubes
Posted: Wed Jan 22, 2014 2:34 pm
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Yep, and cigarettes weren't bad for your health either back in the day. Great times! :wink:

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Post subject: Re: swapping out tubes
Posted: Wed Jan 22, 2014 4:06 pm
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Everyone tweaks the pins of a 9-pin mini tube. Tube pin straightner work wonders. I put a little Deoxit on the straightner and clean the pins, as I'm inserting the tube.

http://www.ebay.com/itm/GC-7-and-9-Pin- ... 3cdb71414d


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Post subject: Re: swapping out tubes
Posted: Wed Jan 22, 2014 10:59 pm
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+1 for the tube pin straightener


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Post subject: Re: swapping out tubes
Posted: Thu Jan 23, 2014 2:59 pm
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I pull lightly on the pins with a fine grain sanding paper before inserting. It ensures contact.


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Post subject: Re: swapping out tubes
Posted: Fri Jan 31, 2014 7:50 pm
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Aspiring Musician
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My el84's do not quite fit under the retaining thingy in the blues jr. It sits at a bit of an angle. I could probably fix it by bending it out slightly. The originals (after much macro work) appear to be sovteks as well so I'm surprised they didn't completely fit. I bought EL84s and not BMW2002Ti's recommended EL84Ms. Perhaps that is the issue.

Otherwise they work great. The old ones looked a bit cooked. I don't know that I needed to replace my 12ax7s but I did.

I still get noise when the reverb is turned up at all (like above 0) so at this point I'm assuming I need to order a new tank. I have a HOF reverb that I like quite a lot but I also like having a properly functioning amp.


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