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Post subject: SCXD bias adjustment
Posted: Wed Dec 30, 2009 10:40 pm
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Has anybody done a bias adjustment on the SCXD?
I have a set of tubes on the way and was hoping for a heads up on this amp.
I was hoping to be able to put in a bias adjustment pot.


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Posted: Wed Dec 30, 2009 11:20 pm
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Are they the same tubes as you had in it? If so then no you won't need to bias, if not then yes you will it is pretty easy to do.


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Posted: Thu Dec 31, 2009 12:12 am
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Have a new set of JJ`s on order.

The amp is biased really cold now with the stock tubes at 14.2 mA.

I didn`t see a bias pot inside so I will need to know which resistor to replace with a lower value and add a bias pot for easy future adjustments.


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Post subject: RE: Bias Adjustment Pot
Posted: Thu Dec 31, 2009 4:00 am
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The Bias Adjustment Pot on the Super Champ XD is located right behind the speaker input jack and is blue. Mine came from the factory biased "hot" at 28 per tube. I set it back down to 20 per tube and now it sounds great but I can't fry eggs on it now...........

Happy New Year,
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Posted: Thu Dec 31, 2009 8:34 am
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OK great I saw that blue pot but was unsure if was for the bias.Looks like I am set now.That`s the info I was after right there man.

Got the new JJ tubes in and biased. :D


Last edited by maxoom on Thu Dec 31, 2009 9:19 pm, edited 1 time in total.

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Posted: Fri Jan 01, 2010 7:14 am
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bbrodie wrote:
airbornestrat wrote:
Are they the same tubes as you had in it? If so then no you won't need to bias, if not then yes you will it is pretty easy to do.


You should ALWAYS check the bias when you change power tubes unless the amp is cathode biased. Tubes vary even by the same manufacturer. If you are biased too hot for the new tubes you'll kill them in short order. Too cold and they'll sound like crap forever.



Did I sound like I had no clue about biasing? I just didn`t know where the adjustment pot was and that has been answered now.

A big thanks to wrfabus for giving me the info I really needed.


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Posted: Fri Jan 01, 2010 10:16 am
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maxoom wrote:
bbrodie wrote:
airbornestrat wrote:
Are they the same tubes as you had in it? If so then no you won't need to bias, if not then yes you will it is pretty easy to do.


You should ALWAYS check the bias when you change power tubes unless the amp is cathode biased. Tubes vary even by the same manufacturer. If you are biased too hot for the new tubes you'll kill them in short order. Too cold and they'll sound like crap forever.



Did I sound like I had no clue about biasing? I just didn`t know where the adjustment pot was and that has been answered now.

A big thanks to wrfabus for giving me the info I really needed.


Chill Dude. No need to get snarky...

Even though you're the expert, I'm sure not. That just looked like a bit of friendly help, and since I DON'T have any clue about biasing, I appreciate the answer. Ya know, there are other folks besides the OP that read these posts and pick up some good info. So I give a big thanks to a couple of guys that took the time to make me a little smarter.

RickyD

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Posted: Fri Jan 01, 2010 11:50 am
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I think that you are going to really be pleased with JJ tubes. I put a full retube kit from eurotube.com in my HRDLx a little over a year ago, and have been extremely pleased with the result. The JJ tubes really took out the ice picky highs and made the OD channels much more useable.

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Posted: Fri Jan 01, 2010 3:00 pm
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RickyD wrote:
maxoom wrote:
bbrodie wrote:
airbornestrat wrote:
Are they the same tubes as you had in it? If so then no you won't need to bias, if not then yes you will it is pretty easy to do.


You should ALWAYS check the bias when you change power tubes unless the amp is cathode biased. Tubes vary even by the same manufacturer. If you are biased too hot for the new tubes you'll kill them in short order. Too cold and they'll sound like crap forever.



Did I sound like I had no clue about biasing? I just didn`t know where the adjustment pot was and that has been answered now.

A big thanks to wrfabus for giving me the info I really needed.


Chill Dude. No need to get snarky...

Even though you're the expert, I'm sure not. That just looked like a bit of friendly help, and since I DON'T have any clue about biasing, I appreciate the answer. Ya know, there are other folks besides the OP that read these posts and pick up some good info. So I give a big thanks to a couple of guys that took the time to make me a little smarter.

RickyD


Really, Chill, If you can't find the bias point or the bias pot without asking here, maybe you shouldn't be messing around inside an amp.

airbornestrat, you shouldn't tell people it's okay not to check the bias if you you the same tube manufacturer. No need to get your panties in a knot because some disagrees with you. Newbies need good advise.


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Posted: Fri Jan 01, 2010 4:25 pm
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Putting aside the petty bickering (please?), Are there any easily understood guides for biasing tubes in a guitar amp (specifically a SCXD)? I would rather a pro do it, but I will likely have to do it myself should it become necessary. I have some small familiarity with tubes, my late dad was an electronics engineer and I remember when I was a kid him dealing with replacing bad tubes in all our TV's in the pre-solid state days, taking trips to the local electronics store to use their tube testing machines. With a proper guide, I am fairly confident I could do it.


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Posted: Fri Jan 01, 2010 4:55 pm
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http://www.eurotubes.com/euro-Generic-Bias.htm

Try here, these guys have good info.

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Posted: Fri Jan 01, 2010 5:18 pm
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63supro wrote:
RickyD wrote:
maxoom wrote:
bbrodie wrote:
airbornestrat wrote:
Are they the same tubes as you had in it? If so then no you won't need to bias, if not then yes you will it is pretty easy to do.


You should ALWAYS check the bias when you change power tubes unless the amp is cathode biased. Tubes vary even by the same manufacturer. If you are biased too hot for the new tubes you'll kill them in short order. Too cold and they'll sound like crap forever.



Did I sound like I had no clue about biasing? I just didn`t know where the adjustment pot was and that has been answered now.

A big thanks to wrfabus for giving me the info I really needed.


Chill Dude. No need to get snarky...

Even though you're the expert, I'm sure not. That just looked like a bit of friendly help, and since I DON'T have any clue about biasing, I appreciate the answer. Ya know, there are other folks besides the OP that read these posts and pick up some good info. So I give a big thanks to a couple of guys that took the time to make me a little smarter.

RickyD


Really, Chill, If you can't find the bias point or the bias pot without asking here, maybe you shouldn't be messing around inside an amp.

airbornestrat, you shouldn't tell people it's okay not to check the bias if you you the same tube manufacturer. No need to get your panties in a knot because some disagrees with you. Newbies need good advise.


63,
I asked the same question to one of the Fender Amp techs at the guitar shop locally and he stated that if you are using the same tubes(manufacturer) as those in your amp then there is no need to rebias...if someone has issues with that, I have no problem. I don't have my panties in a knot about what anyone has said here, I think you might be confusing me with someone else..:) it is all good this forum is a great place with a ton of great folks. I am not about to ruin a good thing..:) I only get my panties in a knot if you say I play an LP...LOL
ABS

edited for typo


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Posted: Fri Jan 01, 2010 5:24 pm
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I'd look for a new tech. Seriously. I've done exactly that a long time ago and lost a quad set in my Twin because the tubes weren't even close to the identical set they replaced. A very expensive lesson.


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Posted: Fri Jan 01, 2010 5:32 pm
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63supro wrote:
I'd look for a new tech. Seriously. I've done exactly that a long time ago and lost a quad set in my Twin because the tubes weren't even close to the identical set they replaced. A very expensive lesson.


I appreciate the advice and did some searching here is a really good thread for folks..:)
[url]http://www.agileguitarforum.com/viewthread.php?tid=11815&page=1
[/url]


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