Help with power tubes

[grunge782]

So what do I do exactly with these KT77's at 38ma? I know I slide it over to el34, but since it is a fixed bias, do I simply just put them in there?

 

[R_ADKINS80]

Yup that's it. Some people like to run it on tube rectifier mode as well t keep it a little cooler but you don't have to. All the diodes will do is run them a little on the hot side but it is perfectly alright.

 

[Old BF Shred]

So what do I do exactly with these KT77's at 38ma? I know I slide it over to el34, but since it is a fixed bias, do I simply just put them in there?

I am curious....how do you know they are "38ma"? Did you measure them in that amp? Or was it labelled as such?
I ask because different suppliers use different amps with different voltages other than Mesa's. I learned this the hard way...
I would sincerely recommend that you measure (or have measured) your idling current after you install them.
The good news is that once you know it you can use that as a "reference point" to determine what you need from that same supplier. Of course, if you change suppliers, you will need to start the process over again.

Good luck with that!

 

[grunge782]

So what do I do exactly with these KT77's at 38ma? I know I slide it over to el34, but since it is a fixed bias, do I simply just put them in there?

I am curious....how do you know they are "38ma"? Did you measure them in that amp? Or was it labelled as such?
I ask because different suppliers use different amps with different voltages other than Mesa's. I learned this the hard way...
I would sincerely recommend that you measure (or have measured) your idling current after you install them.
The good news is that once you know it you can use that as a "reference point" to determine what you need from that same supplier. Of course, if you change suppliers, you will need to start the process over again.

Good luck with that!

It is based just on what TubeDepot said. How do you measure that? And what do I even do if it's a fixed bias? Is there a certain limit that the reading can't go over or something?

 

[Old BF Shred]

I usually buy from Tube Depot and I like them, but I have had bad tubes from them, too. First off, did you tell them what amp these are to go in? What brand are they? Some brands are more tolerant to high idle current that others. I have found SED =C= to be very tough, but had issues with JJ and NewSensor's "Mullard re-issue".
Even on those brands, a lower rating may have worked just fine. 38ma is "borderline", IMHO...could go either way. I had JJ's in 39ma and they "redplated" right after the warranty expired. But they were el34, NOT kt77's so we are not really comparing apples to apples.
If they said that the 77's at 38ma would work, then they are probably right...if they did not tell you this, you may wish to give them a call and discuss your amp specifically. They have been very helpful with me, and BTW, they gave me credit for those JJ's so they are a good place to deal with; very fair and they want to do right for their customers.
A few minutes call can save you piece of mind.

Good luck!