Bare Knuckle Pickups Forum
Forum Ringside => Guitars, Amps and Effects => Topic started by: Yamhammer on November 21, 2008, 01:48:52 PM
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I want to replace ALL the stock ENGL tubes
for new and fresh JJ Tubes.
1). How many tubes do I have to change?
2). Which JJ Tubes do I need?
Thanks in advance.
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you need 4 12AX7s and 2 6L6's
And a biasrite or similar and a multimeter, and an insulated screwdriver, a steady hand and COMPLETE AND TOTAL CERTAINTY THAT IF YOU TOUCH A SINGLE THING IN THERE WITH YOUR FINGERS YOU WILL DIE.
Cant stress that enough. Be hyper-carefull. 50mA (roughly the screamers cathode current, I seem to recall from when I biased mine. Probably horribly wrong though, the memory isnt exactly clear) is you-need-a-paramedic-on-the-scene levels. 6mA is lethal.
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Thanks very, very much for your info.
I'll leave the job to a specialized tech.
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Well, dont be too scared, not everything in there will kill you. You just have to assume it all will, because a lot of it will.
But yeah, if youre in the least unsure, take it and the valves to a tech.
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Not to question your far superior knowledge about amps MDV, but will 50mA really kill you? Wiki tells me the minimum a human can even feel is 1mA
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You mean mythbusters lied to me!?!?!
I think thats the value for accross the heart, which is quite possible, holding a chassis or any other form of ground with one hand, and you fumble onto the circuitry with the other.
Mayhaps I'm wrong though. If anyone can confirm or deny, shout up.
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If anyone can confirm or deny, shout up.
Shut up MDV, you're talking nonsense.
He should test ever connection with his tongue, while standing barefoot in a metal tray of salt water...
(then the HD-loaded silverburst LP will be MIIIIINNNNNEEEEE mwahahaha!) :)
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If anyone can confirm or deny, shout up.
Shut up MDV, you're talking nonsense.
He should test ever connection with his tongue, while standing barefoot in a metal tray of salt water...
(then the HD-loaded silverburst LP will be MIIIIINNNNNEEEEE mwahahaha!) :)
:lol:
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http://en.wikipedia.org/wiki/Electric_shock#Lethality_of_a_shock
i know that the current, especially if it goes through the heart, doesn't have to be very much to be lethal. i'd stick with mark's advice, assume it's lethal unless you're 100% sure it won't be.
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Does 50mA stand for 50 mini amps? Micro amps?
I was thinking mains electricity is 13A which is lethal but i've had a few jolts over the years and it hasn't done me any harm :crzy: Plus car ignitions at the spark plug can be very powerful not sure is it 3 amps?
Each year the Darwin Awards have people who have died putting 9v batterys on their tongue.
My brother had a shock from a 3 phase circuit and lived which is seriously lethal. So perhaps its like the lottery.
I'd use a insulated screw driver like Mark says, those transformers are putting out some big voltages.
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Voltage doesnt actually hurt you though. Current does.
But yeah, the screamers plate voltage is about 500V, so if it in fact does, then thats more than twice mains.
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am i missing something... or can't you just unplug the amp before working on it, thus taking away the dangers?
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Does 50mA stand for 50 mini amps? Micro amps?
I was thinking mains electricity is 13A which is lethal but i've had a few jolts over the years and it hasn't done me any harm :crzy: Plus car ignitions at the spark plug can be very powerful not sure is it 3 amps?
Each year the Darwin Awards have people who have died putting 9v batterys on their tongue.
My brother had a shock from a 3 phase circuit and lived which is seriously lethal. So perhaps its like the lottery.
I'd use a insulated screw driver like Mark says, those transformers are putting out some big voltages.
Wear latex gloves too - or washing up gloves :wink:
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am i missing something... or can't you just unplug the amp before working on it, thus taking away the dangers?
You need to be getting a reading from it to bias it.
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am i missing something... or can't you just unplug the amp before working on it, thus taking away the dangers?
You need to be getting a reading from it to bias it.
ahh... biasing. forgot about that. my amp is fixed bias, which would explain why i forgot about that.
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What about turning it on, getting a reading, turning it off, making adjustments?
Or does the charge stick around after you turn it off?
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Yeah, electricity stays in the amp. I think it's the caps that actually hold it.
You can't be too carefull. My advice: Take it to a tech.
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What about turning it on, getting a reading, turning it off, making adjustments?
Or does the charge stick around after you turn it off?
Good theory, but thats a non-starter: you need to know what effect your adjustments have made, and theres no way to read that with the amp off. Plus as ratrod says, there are caps in there that hold enough charge to kill you (whatever that is!!) as well. I dont know how long that takes to dissipate - it could be minutes, it could be days.
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What about turning it on, getting a reading, turning it off, making adjustments?
Or does the charge stick around after you turn it off?
Good theory, but thats a non-starter: you need to know what effect your adjustments have made, and theres no way to read that with the amp off. Plus as ratrod says, there are caps in there that hold enough charge to kill you (whatever that is!!) as well. I dont know how long that takes to dissipate - it could be minutes, it could be days.
You could easily calculte the discharge of the capacitors, but then you might aswell be a tech haha.
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The capacitors still hold charge even when the amps off as well I think..
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Indeed they do. I count myself lucky that I survived a shock from my 30w Laney when I accidentally put my finger across the on/off switch connections some years back. I feel sick just thinking about it.
Maybe some of the amp techs/builders/tinkerers here can tell us the best way to discharge the caps before working on them?
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Take it to a tech and then maybe you could try out different valves as they have their own sound.
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^ so, johnny, if your koch is acting up and you aren't sure what's wrong, you should take it to a professional? :lol:
also, what's a koch tube? o_O
Does 50mA stand for 50 mini amps? Micro amps?
milli (a thousandth) :)
Good theory, but thats a non-starter: you need to know what effect your adjustments have made, and theres no way to read that with the amp off. Plus as ratrod says, there are caps in there that hold enough charge to kill you (whatever that is!!) as well. I dont know how long that takes to dissipate - it could be minutes, it could be days.
yeah, the caps will hold charge, that's what they're for (to smooth ac ripple etc. among other things). depends on the amp, the cap, chance too i guess... i think some amps may have a resistor somewhere around the caps which will self-drain the caps, but it's certainly not every amp, and it'd be safer to manually drain the caps anyway just as good practice.
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^ so, johnny, if your koch is acting up and you aren't sure what's wrong, you should take it to a professional? :lol:
also, what's a koch tube? o_O
Does 50mA stand for 50 mini amps? Micro amps?
milli (a thousandth) :)
Nah my Kochs fine Dave just fine. I was thinking that by taking it to a pro' I may be putting it at more risk....hmm, we should leave that one as it may contain extracts of the lyrical content of a carcass song..
Ah a milli amp. Thanks for that :D
Koch valves are just the usual rebranding of other valve manufacturers products. I can't remember who makes them now.
Anyway here's my naked Koch!! :lol:
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^ i meant that koch tube sounded like something which should be x-rated... :lol:
i guess it depends on what you mean by a professional... i meant a doc, but maybe you meant something else... :lol:
getting back to the serious stuff, that's pretty cool that you can mix and match power tubes in the powertone. that's one of the few things about my engl that i wish were different- it seems to take 6L6s/5881s, and that's your lot... :)
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^ i meant that koch tube sounded like something which should be x-rated... :lol:
:lol: :lol:
Ahh, Koch jokes are as old as this forum but that was a great new take on one!!
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:D :drink: