Bias - need more help

[RVA]

I will start by saying I am sick of tube amps...again.

So when I got my Ceriatone amp, I set the bias at 23 each by adjusting the bias adjustent pot until they matched (I have attached the Ceriatone manual. See pages 11-13 for bias directions)

Today I changed the tubes. I had a matched quad handy, but I only needed 2 tubes. I grabed 2 and could not get them even close - closest was about 15mv away. I took away the high tube and grabbed another from the quad. Now I only get the mV between the tubes even at 17 mV - far shy of the 24 mV it was. What the hell is going on. I am so frustrated.

All help is greatly appreciated as I have run out of patience.

 

[Thatbastarddon]

It is generally considered “acceptable” to have around a 2mV variance. That said, you are having a rough time of late, aren’t you?

 

[RVA]

It is generally considered “acceptable” to have around a 2mV variance. That said, you are having a rough time of late, aren’t you?

Yes. I love working on guitars. I hate working on amps. I am just about done with this tone chase.

 

[Thatbastarddon]

If you take one up to 24mv, how far off is the other?

 

[RVA]

If you take one up to 24mv, how far off is the other?

About equally down

 

[Thatbastarddon]

About equally down

I’m sorry, what?
If you set the bias adjustment to one tube at 24mv, what does the second tube read?

 

[RVA]

I’m sorry, what?
If you set the bias adjustment to one tube at 24mv, what does the second tube read?

If I raise a 17 to 24, the other one goes to about 10

 

[Thatbastarddon]

Measured on each power tube, at the points specified?

 

[RVA]

Measured on each power tube, at the points specified?
View attachment 25203

Yes sir. Not exactly user freindly! Resisters on sockets as bias test points? Really?

 

[Thatbastarddon]

I use probes....like these...

Because I’m lazy like that....
I’ve not done my 6V6 amp with it yet.
Edit: I have done 6L6, and EL34 amps with them though.

 

[RVA]

I use probes....like these...
View attachment 25204
Because I’m lazy like that....
I’ve not done my 6V6 amp with it yet.
Edit: I have done 6L6, and EL34 amps with them though.

I just remeber that I have one! I will buy a second.

I emailed Nik from Ceriatone. I read that he is very nice about helping out

 

[RVA]

I am OK now. I must have been measuring something wrong back there. They now move together - both up or down with the pot. I got them to 24 each and it is quiet. Thanks!

 

[Thatbastarddon]

I am OK now. I must have been measuring something wrong back there. They now move together - both up or down with the pot. I got them to 24 each and it is quiet. Thanks!

Thank goodness!!!
I feel better now!
I know that it’s been frustrating for you sir, but I’m glad to see your tenacity!

 

[RVA]

Thank goodness!!!
I feel better now!
I know that it’s been frustrating for you sir, but I’m glad to see your tenacity!

I really appreciate your help and support. I will learn if it doesn't kill me. I caught a 110v zap tonight!! After being told to be careful so many times, it scared the crap out of me!!

 

[syscokid]

I really appreciate your help and support. I will learn if it doesn't kill me. I caught a 110v zap tonight!! After being told to be careful so many times, it scared the crap out of me!!

What did you touch?

Both hands in the chassis?

 

[Thatbastarddon]

I really appreciate your help and support. I will learn if it doesn't kill me. I caught a 110v zap tonight!! After being told to be careful so many times, it scared the crap out of me!!

What did you touch?

Both hands in the chassis?

Yeah! One hand in the pocket sir! No death!
I’ve been bitten by lab equipment, and a TV....no fun.

 

[RVA]

What did you touch?

Both hands in the chassis?

Yeah! One hand in the pocket sir! No death!
I’ve been bitten by lab equipment, and a TV....no fun.

I am fairly certain I touched the connection to the fuse. One bias point is under them. I was far clear of the caps

 

[Thatbastarddon]

I am fairly certain I touched the connection to the fuse. One bias point is under them. I was far clear of the caps

Well...you’re still typing...so....ok.

 

[syscokid]

I am fairly certain I touched the connection to the fuse. One bias point is under them. I was far clear of the caps

Having different type of probe leads is useful. The spring loaded hook clip might be a good choice in this particular biasing situation. Clip the probes to the testing points before you plug in the AC cable.

 

[RVA]

Having different type of probe leads is useful. The spring loaded hook clip might be a good choice in this particular biasing situation. Clip the probes to the testing points before you plug in the AC cable.

View attachment 25207

I have used those before. Great idea!