#1
Well our Laney needs new tubes. So we have got a JJ set with EL34Ls (right now it has EL34s). But the thing is that the cheap b*stards at Laney doesn't want people to bias the amps themselves, so there's no external bias pot and bias is going to be pretty hard for us to do. And since our band is quite poor (especially after buying new tubes) I wonder if I would have to bias? According the manual if you replace it with the same tubes, no bias is required and EL34Ls are EL34s after all...
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#2
The Laney manuals and website do suck when it comes to biasing.

There *should* be a bias pot inside. Have a look.
#4
Well it was a shame we didn't get a bias probe when we bought the tubes.

Is there any way to measure bias without one?
Quote by stratman_13
It's okay Gabel. You kick ass.



18watter video demo

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Recognised by the Official EG/GG&A Who To Listen To List 2009
#5
You can do it with a multimeter, but you'll have to poke around more inside, and generally know what you're doing.
#6
Hello Gabe,
You should bias the amp. Just to be on the safe side and its about time you learn.
Few questions for you. Biasing will be easy once we know what all were working with here.
1. What Laney is it?
2. Are you comfortable with removing the chassis and working(very little) on it?
3. Do you have a digital multimeter?

Bias probe, you can do without, but it makes biasing a lot easier. This is the one I use
http://www.amp-head.com/product_info.php?cPath=21&products_id=30
I know that you are in Sweden, so if I were you, I would just buy from somewhere local. You can even make your own.
#8
^That is my amp. Though I didn't make a lot out of that manual, sorry.

Well actually, what would I need to make a bias probe? I already have a multimeter and I could get tube sockets, resistors and so on. I'm used to soldering, so it would be no problem.

Actually making my owb bias probes should be easy. I would need two tube sockets, which I can order and then I would need a tube base, which I could take from the old EL34s which are in the amp. Then I jsut need some resistors and other things. Does anybody have a schem or isntrucions for making my own?
Quote by stratman_13
It's okay Gabel. You kick ass.



18watter video demo

My band

Recognised by the Official EG/GG&A Who To Listen To List 2009
Last edited by Gabel at Feb 12, 2008,
#9
I have instructions on a "permenant" biasprobe. This is what I used to do with my amps.

To mod the amp, you will need to get some 1 Ohm, 1 Watt(or bigger) precision resistors(as many as you have output tubes). Precision resistors are accurate to 1% of stated value. If your electronic parts store won't let you measure before you buy or doesn't have 1%'ers, buy a bunch and measure them. You need exactly 1 Ohm.

1. Remove the wire or solder joints between the cathode and ground on all output tubes. (Pin 8 on 6L6, 6550,EL34... pin 3 on EL84/6BQ.

2. Solder a 1 Ohm resistor between the cathode and ground. Ohm's Law states, I=E/R (current= voltage/resistance). If a resistance is 1 Ohm, then I=E, because any number divided by 1 equals that number.

3. Plug in the guitar and speaker, Connect one of your meter leads to the chassis side and the other lead to the tube side of the 1 Ohm resistor. Use biasprobe charts to determine the approximate proper current draw for your amp.

4. Set the bias pot to draw a bit more current, then play and listen. As long as you pay attention, you're ok. If the plates glow red, you're too hot. If the sound is gravelly, you're too cold.

5. When you get your best sound on both clean and dirty tones, leave the bias where it is and close up the amp.

Like I said, I've done this on two of my amps before i got my bias probe. Any questions pm or email me at mingpau@connecttime.net
I will also try and find instructions on actually makeing a "portable" bias probe.

Here are some helpful websites for bias settings:
http://www.webervst.com/tubes/calcbias.htm
http://www.eurotubes.com/euro-Generic-Bias.htm
#12
Well I know what a bias pot looks like (it's a black trim pot).

I will probably go with the bias probe way, so I can use it with more amps.
Quote by stratman_13
It's okay Gabel. You kick ass.



18watter video demo

My band

Recognised by the Official EG/GG&A Who To Listen To List 2009
#14
^Yeah and thanks a lot for them!


Me and my dad has now ordered a Eurotubes bias probe. He felt it was the best thing to do really.
Quote by stratman_13
It's okay Gabel. You kick ass.



18watter video demo

My band

Recognised by the Official EG/GG&A Who To Listen To List 2009
Last edited by Gabel at Feb 13, 2008,
#16


One thing, I haven't seem to ahve gotten any good values on what value I should set the bias on the amp.
Quote by stratman_13
It's okay Gabel. You kick ass.



18watter video demo

My band

Recognised by the Official EG/GG&A Who To Listen To List 2009
#17
Well you need to get your plate voltage than look at a biasing chart.
http://www.webervst.com/tubes/calcbias.htm
On this site, on the top you can enter in your plate voltage, class and tube type. Then it will give your bias at 70%.
Or scroll down and find the chart for your tubes(EL34). Find your plate voltage and you will see your bias settings for 70%, 60% and 50%.

So an example is, EL34 or E34L's(both 25W tubes) at 400V, your bias setting will be 44mA.

Just incase, you find your plate voltage this way:
Let your amp warm up. DMM on volts. Place the positive(red) on pin 3 and negative(black) on a ground. This will give you your plate voltage.
Last edited by The Real Ming at Feb 13, 2008,