bias probe

[nepalnt21]

ok lets say one has a bias probe (a tube socket hooked up to +/- leads and banana plugs for use in a multimeter detecting current), but an amp with more then one power tube.

can one use the single bias probe, but leave the other tube plugged in like regular, and take the current reading for one tube at a time, and average out the amperage between them, or does one have to purchase a bias probe and multimeter for each tube socket?

 

[wixedmords]

Re: bias probe

Do the adjustment with the hottest tube but recheck the cooler one.

 

[wixedmords]

Re: bias probe

BTW, to check each tube with a one socket probe you will need to spend some time waiting for the tubes to cool before swapping the socket. A two socket probe allows you to flip a switch and check the other (another) tube.

One multimeter needed either way.

 

[nepalnt21]

Re: bias probe

ok


thanks

 

[Scott_F]

Re: bias probe

Or you can open up the amp and touch a couple of pins. Just gotta guess the right ones.

I have had a single weber bias probe a long time and there's times where I just want to keep an eye on a power tube for a few and it's a very handy and (SAFE) way to check your bias.

Stay Safe.

 

[Red_Label]

Re: bias probe

I have a dual Amp Head bias probe. But I frequently use it on my two amps with 4-EL34s. So I put the probes on the paired sockets and take readings. Then cool them down, swap around, then take readings. I usually allow the amp to warm-up (while playing) to full operating temp, before taking readings. Then I'll play for a bit, and take another reading. And repeat until I feel that I've got a fair idea of what the tubes are averaging.