Bias the amp

[StrangeSound]

Good day!

I checked the videos on eurotubes out which show how Bob sets the bias on some amps. I mailed him and he said on a Engl Screamer it would be the same procedure like the in Carvin V3 video.

http://www.eurotubes.com/euro-video.htm

It looks easy but I got one question, where or how do I have to connect alligator clips to ground the thing? On the Marshall and Fender videos he says how to use the alligator clips but I couldn't see the clips in the carvin video.

I won't play with the bias on my amp now but I want to do it myself if needed in the future.

Thanks mates!

 

[StrangeSound]

Re: Bias the amp

Rid, help me please

 

[Vasshu the humanoid typhoon]

Re: Bias the amp

Hehe well our guy who is a tubeamp wiz is currently unavaiable right now, but he is teaching me some stuff about tubeamps.
To locate the ground, well get a meter that can beep when there is connection, that is an easy way to locate the ground...
But still...uh I really hate those highvoltage things

 

[StrangeSound]

Re: Bias the amp

Yeah but it's possible to do it on your own!

I just need that info...I'll write Bob another mail I think.

 

[Gearjoneser]

Re: Bias the amp

It's a good idea to buy a bias tool. It's just a socket that goes between the amp and tube, with 2 leads hanging off it, which plug into a volt/mA meter.
I have the mA version. I think I paid $15 for it. I use it as a guide, so that 6L6's are around 32-33mA and EL-34's are around 36-38. I go by ear, but try to keep the numbers around there. When the amp sounds big, bold, and strong, it's usually where it should be.

 

[STRATDELUXER97]

Re: Bias the amp

It's a good idea to buy a bias tool. It's just a socket that goes between the amp and tube, with 2 leads hanging off it, which plug into a volt/mA meter.
I have the mA version. I think I paid $15 for it. I use it as a guide, so that 6L6's are around 32-33mA and EL-34's are around 36-38. I go by ear, but try to keep the numbers around there. When the amp sounds big, bold, and strong, it's usually where it should be.

GJ is right and that's the safer,smarter way to bias your amp! I have 1 ohm cathode resistors across my output tube pins and I just read across the resistors and setup my bias that way..It's called "Cathode Bias Adjustment"..Ken Fischer told me how to do this back in like 83 or so..

 

[Zhangliqun]

Re: Bias the amp

I've been thinking about getting the Weber Bias Rite but so far the only amps I own (Fender Hotrods) are pretty easy and safe to bias, you don't even have to take the chassis out. They have a "Bias Test Spot" on the PC board within easy reach so it's easy to take readings.

But if I ever get a vintage or other older amp that requires chassis removal, the Weber won't be far behind...

 

[STRATDELUXER97]

Re: Bias the amp

I've been thinking about getting the Weber Bias Rite but so far the only amps I own (Fender Hotrods) are pretty easy and safe to bias, you don't even have to take the chassis out. They have a "Bias Test Spot" on the PC board within easy reach so it's easy to take readings.

But if I ever get a vintage or other older amp that requires chassis removal, the Weber won't be far behind...

Yeah....the guys that goof around with tube amps know where to bias and also where to stay away from...The novice guys are always better off doing the bias or any type of work inside of amps the safe way!

My 73 50 Watt Hand Wired Marshall That I Re-Did Last Year.Was PCB..

 

[StrangeSound]

Re: Bias the amp

Thanks guys for the input!

Bob wrote back:

Hi Adrian:

There are no alligator clips involved when you use a bias probe. You do not use the standby method with the Engl, you need to use a bias probe.

Thanks


Bob

So, All I need is a volt/mA meter and something like this, right? The Engl has 2 6L6 tubes but one bias probe is enough.

And a (plastic) screwdriver to adjust the thing. I won't touch anything else on the amp, just do the necessary work.

 

[Scott_F]

Re: Bias the amp

https://taweber.powweb.com/biasrite/br_page.htm

Several years back, I just bought a single little head with two wires coming off of it. It works like a champ when you're in a hurry and don't want to drop a chassis. They also make one now that has a switch on it for reading plate voltage. There's even one now that can look at EL84 9-pin sockets.

 

[Gr8Scott]

Re: Bias the amp

Anyone know a good source for a bias probe? I have a really good multi-tester, so I don't need the Weber BiasRite. I just need a good probe that's equipped with a 1 ohm resistor already in place.

 

[Fresh_Start]

Re: Bias the amp

You could make your own: Hoffman bias checker

Chip

 

[Gr8Scott]

Re: Bias the amp

Thanks fresh! Placed my order today for the parts, but I'm not gonna do the dual banana plug thing as my tester might not work with that adapter. I bought two test points instead.

 

[pixelpusher]

Re: Bias the amp

You could make your own: Hoffman bias checker

Chip

I notice these plans do not call for the 1ohm resistor is that dangerous?

I have the groove tubes socket thing (i paid the premium because it comes with a guide to biasing) but it is super flimsy and won't read EL34's for some stupid reason. so i want to make another one. I already have all the parts lying around to make the one in the plans if not having the resistor is not an issue....

 

[StrangeSound]

Re: Bias the amp

Damn, I opened the Screamer but couldn't find the bias trimpot..where can I find it? I'm quite sure it has a trimpot!

 

[Scott_F]

Re: Bias the amp

Anyone know a good source for a bias probe? I have a really good multi-tester, so I don't need the Weber BiasRite. I just need a good probe that's equipped with a 1 ohm resistor already in place.

YOu didn't scroll down far enough on the WEber page. He sells just the probe and it will do the ma thing plus high voltage (which is mandatory if you want to bias correctly, not just a wild ass guess)

 

[Fresh_Start]

Re: Bias the amp

Just got an email from Mission Amps showing the ultimate bias device. It costs a lot but is awesome in terms of features.

Chip

 

[wixedmords]

Re: Bias the amp

which is mandatory if you want to bias correctly, not just a wild ass guess

Agreed and seconded.

You need high voltage capability (200-600V) to get plate voltage.

I have great luck with my SRS tools from Ebay. They won't do plate voltage. That has to be done the old fashioned way.

 

[jeremy]

Re: Bias the amp

i have a weber bias rite head (i use my own multimeter) its a great tool and easy to use. in general i tend to bias a little hotter than joe said.

 

[DesertRose]

Re: Bias the amp

How to locate the bias test point for older fender amps .. darn, it has no markings !!! anyone ? =)