Video how to bias vintage modern!!!

[surfnorthwest]

Indeed, very nice video. I was going to make a biasing video but you beat me to it. Well, if it's found necessary to have a 2466 bias video, I could do that.

One thing I'd suggest adding, is if you use the speaker as a load while biasing, be sure and turn the master volume to zero to lower the possibility of noise issues while having the chassis out of the wood.

I would encourage you to still make one for the 2466 so we don't have guys setting the tubes to hot. Plenty of room for another video here.

[SteveD]

hey Steve thanks for your kind words....i know my english sucks but i'm trying...if i died touching those resistors at least i would be a dead fried rockstar... : something like fried chicken you know....

anyway i have a question for you if you don't mind....when i biased my VM i noticed that i had almost 2mA difference between the 2 tubes i'ts ok that? i think the stock tubes are pretty well matched.....how much would be the biggest difference between the 2 tubes if it is not matched?

thank you

2mA is pretty decent. As long as both sides are between 43 and 48mA on the 2266/C and 72 and 80mA on the 2466 it is within tolerance. That is not to say you would have to change them if they eventually drift outside these ranges, they are just the figures we set for the new valves when the amps leave the factory. You can see that the range is within -10% of the highest figure. It's not recommended exceeding the highest figure!

Bottom line is if it sounds good then stick with it until it doesn't; then think about changing valves if you can't get it in check with a rebias.

[tellus1]

That's a great thing to be able to do myself! I'm just wondering about specific parts that you can or cannot touch. After you have done the BIAS adjustment and turned the power off the amp, is it ok to touch it immediatedly, or are there certain areas that I shouldn't touch during fitting it back into the wooden chassie?
I still have some years to live, so I want to make sure what parts I can or cannot touch.
One other question I have is if the different Power tubes differ too much, what shall I do then?

[SteveD]

My advice would be don't touch anything else other than CON10 (the test points) and TRIM 1 (the adjust point) to be safe, even after you have just turned the amp off. You can leave the amp to cool down for a half hour or so after switch off but still only handle the chassis when reassembling.

By the way for anyone who's interested, the middle pin (pin 2) of CON10 is also a ground point so don't worry if you touch the outer pins to this middle pin by mistake when probing; there's only a very small potential between them (the bias voltage!)so no damage can occur. You would simply be shorting out the 1 ohm resistor that the bias voltage is developed across in order to measure it (so the reading would be 0V).

When we bias at the factory, we have a plug that fits onto CON10 then we simply select which side we want to measure, the centre pin is obviously where the plug gets it's ground reference. Using this middle pin would be a bit fiddly when doing it with meter leads so that is why it is recommended to anchor the meter ground lead to any convenient point on the chassis for a ground reference (use a croc clip or the cage nuts make a good anchor point) thereby facilitating only having to probe with one hand which is safer! Also you can measure and adjust simultaneously.

I would also recommend standing behind the amp during this whole procedure and steady your hand by resting it on the rear panel near the speaker outputs as opposed to hovering over some pretty lethal voltage areas if you approach it from the front (which I always do but I know the keep outs!).

Don't do this in an environment where you could be distracted, like children or pets running around as one slip and by God you'll know about it if your probe hits a high voltage part of the circuit. :high

BE CAREFUL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!DON'T EVER GET COMPLACENT WHEN WORKING ON HIGH VOLTAGE AMPS!!!!!!!!!!!!!!!!!!!!

[beachroadbum]

Hi all,

Thanks for the video! wonderful!

Now here is a question for you steved. I talked with a professional electrian about biasing and he said to wear rubber dishwashing gloves while performing the bias. So in wearing the rubber dishwashing gloves while biasing if your hand does touch lethal voltage would I be ok?

Thanks!

[SteveD]

Hi all,

Thanks for the video! wonderful!

Now here is a question for you steved. I talked with a professional electrian about biasing and he said to wear rubber dishwashing gloves while performing the bias. So in wearing the rubber dishwashing gloves while biasing if your hand does touch lethal voltage would I be ok?

Thanks!

It is an option and they would indeed insulate you from the high voltage ,but, they wouldn't do anything to protect other components from being fried if you short them by letting your probe slip in the wrong place. I thinkl this could be an issue if you don't feel you have to be as careful anymore!

[beachroadbum]

Right on Steve!

Thanks.

[CBoothe]

Hi- I've biased a JVM before but not the VM. Just curious- the JVM has two trim pots- one for each set of tubes. Does the single trim pot adjust all 4 four tubes at once in the 2466?

Thanks

[SteveD]

Yes. Just ensure both pins (1 and 3) measure within the recommended range 72 to 80 mVDC. They may or may not both be the same depending on how well matched they are but as long as they fall within these figures it's within factory spec.

[CBoothe]

SteveD- Thanks! Half the fun I have playing guitar is learning about how to maintain my gear!

[Lavox]

Folks, would anyone be willing to make a video to show us how to bias 2246? If this has been done already I apologize! Can anyone post a link to it please?

If not, while you have all the guts out and the camera on, can you point to this bits that could kill you if you touch them and explain why. Obviously, I'm far too cowardly to give this a go myself, but it might be useful for others.

Cheers.

[chukka09]

DANG IT! The video for biasing the VM has been removed!

Can someone either re-post it or do a new video. I just assumed it would always be there for when I was ready to bias my 2266 so I didn't bother paying enough attention to the details when I watched it the first time awhile ago.

[Lavox]

It's time to bias the 2466 folks.

Anyone have a link to a video or pictures? I've had a search but most seem to be removed.

Ta in advance.

[code39]

Hello Gizmo, is it possible to re upload your video ?
Thanks in advance for your helping ! :)

[code39]

aie... nobody has this video somewhere ?
thanks in advance ! :)