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Changing Tubes

bombidol · 2007-06-08 08:25:49

I recently bought a full set of JJ's for my Peavey 6505+. I was talking to the place I bought em and they said that the Peavys Bias runs pretty cool so the Tubes would be just plug and play. Done it last night but after 2 or 3 mins of play Im getting this bonkers 60's Sci Fi effect through my speakers. Like theres…

08-06-2007 8:25am

#1

bombidol

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I recently bought a full set of JJ's for my Peavey 6505+. I was talking to the place I bought em and they said that the Peavys Bias runs pretty cool so the Tubes would be just plug and play. Done it last night but after 2 or 3 mins of play Im getting this bonkers 60's Sci Fi effect through my speakers. Like theres something wrong somewhere.
I have no idea about Biasing etc anyone know the best place to get it done or the amp checked out in Dublin?

Thanks

Gar

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#2 08-06-2007 12:40pm

SirLemonhead

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You can't bias Peavey amps at all, as far as I know. You're meant to purchase matched sets of tubes from Peavey.

You can of course use whatever other tubes you want in it, I just don't know the specifics.

No idea what'd be causing that weird effect though... try swapping back to your old preamp tubes first, keeping the new poweramp ones in?

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#3 08-06-2007 12:42pm

bombidol

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Theres Biasin yokes on the back of the peavey. This tubes were selected to work specifically with the 6505+

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#4 08-06-2007 12:45pm

SirLemonhead

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Ah right, must have changed things so.

Is it a place on the back for taking bias readings with a multimeter?

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#5 08-06-2007 4:13pm

bombidol

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yeah, I just have no idea how to do that!

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#6 08-06-2007 5:01pm

NeMiSiS

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Is this the back of your amp ? http://www.networks-plus.ca/logo/6505.jpg
TK

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#7 08-06-2007 5:08pm

bombidol

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Thats her alright

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#8 08-06-2007 5:08pm

Beecher

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Is the balanced tube in V5 for the phase inverter?

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#9 08-06-2007 5:11pm

bombidol

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Theres 6 ports together for the smaller tubes and 4 for the larger ones. Which port should the phase invertor be in? fifth one to the left?

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#10 08-06-2007 5:22pm

NeMiSiS

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ASSUME EVERYTHING I AM ABOUT TO TELL YOU IS INCORRECT UNTIL TOLD OTHERWISE BY QUALIFIED AMP TECH

Pull valves one at a time, and REPLACE with the old one, you could have got a gammy valve, so rule that our first.

Make sure you are seating all the valves correctly, if they have numbers on the bottom make sure they correspond to where you are putting them in.

Read this : http://music-electronics-forum.com/archive/index.php/t-1302.html

Says the recommended level should be 31 - 34 mA.

If you pointed someone with a good knowledge of that kinda of thing towards that article it may help..

GUESSING.. which I would not assume is good enough.. you put the multimeter into the black and red.. (I HAVE NO CLUE WHAT THE GND SWITCH MIGHT DO) switch to GND (+) take the reading, switch to GND (-), take the reading, then you 'balance' it with the two little screws where is says "Bias adjust"

LET ME STRESS I AM NO WAY QUALIFIED TO DESEMINATE THIS KIND OF INFORMATION, AND NOTHING I SAY SHOULD BE FOLLOWED UNLESS YOU HAVE A QUALIFIED PROFESSIONAL AMP TECH AT HAND. I IN NOW WAY SUGGEST YOU SHOULD PERFORM ANY OF THIS YOURSELF.

It's very straight forward on a my Marshall, you can do it in 10 minutes.

I can get you the number of a guy who is quite good at that sort of thing, but I would doubt he is cheap, and he is based, near Athy (Kildare). Road trip ?

Lot of disclaiming there..

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#11 08-06-2007 6:39pm

Beecher

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bombidol wrote:

Theres 6 ports together for the smaller tubes and 4 for the larger ones. Which port should the phase invertor be in? fifth one to the left?

Okay, from what I understand* in your amp the phase inverter is actually V6 and this should be the port closest to the power tubes. You should have 5 x ECC83's and a ECC83S. The ECC83S is the balanced tube.

*What I understand may be wrong.

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#12 08-06-2007 6:47pm

SirLemonhead

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You don't need to use balanced tubes for the PI at all, as far as I know.

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#13 08-06-2007 6:57pm

bombidol

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yeah the balanced one is marked on the box. Doesnt matter what order the power tubes (big ones) go in does it?

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#14 08-06-2007 6:58pm

Voodu Child

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If they supplied a balanced tube, you may as well put it in the PI socket.

You won't get amp nuts to agree whether it's important or not, but if you have one, it certainly won't do any harm to use it as the PI.

The guitar shop near Portobello bridge has a fella that's good with amps AFAIK. Aladdins amps is obviously one of the main professional amp techs, but he's pretty pricey.

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#15 08-06-2007 6:59pm

bombidol

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Anyone have a contact for aladdins ?

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#16 08-06-2007 7:01pm

feylya

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http://www.boards.ie/vbulletin/showpost.php?p=2287810&postcount=3

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#17 08-06-2007 7:06pm

Eoin Madsen

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A PI doesn't need to be "balanced". I know people who mod their PI circuits to create a deliberate imbalance because it's supposed to create more even order harmonics.

The problem you've described is not at all typical of a hot or cold bias, so it's something else.

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#18 09-06-2007 3:41am

Eoin Madsen

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bombidol wrote:

Doesnt matter what order the power tubes (big ones) go in does it?

Well, ideally yeah. If they've been tested and marked you should be able to put them in so that the two sides are at their most balanced. But not doing so will not cause a problem like you describe.

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