amperex tubes and mesa tri-axis

[soulreaper_msd1]

I've been tube rolling in 2 different mesa boogie tri-axis, 1 is an earlier model serial # early 3000's the other is mid 5000's which make them both version 2.
with all that said I have tried 10 or more amperex 6dj8/ecc88 and a few other models, absolutely none work they don't light up and no sound . I have bought them from several different people on e-bay with very good ratings.
they all as iam told been tested and are good.
I have ran across other types of tubes besides amperex that didn't work but every amperex doesn't work, am I cursed or is amperex tubes .
I also tried them in my Yamaha t100 and same results.

I do have an old Lafayette 99-5012 tester but have never used it and don't really know how even tho I have the original owners manual and tube manual.

help is all I can say lol. thanks

[Enzo]

The heater is wired different from the 12AX7 types, so if you are sticking them into sockets meant for 12AX7, they won't work.

the 12 volt heaters in 12AX7 can be wired in parallel for 6v operation. pins 4 and 5 are tied together, and pin 9 is the center tap. 6v is applied between 4/5 and 9.

The 6DJ8 has a 6 volt heater wired between pins 4 and 5. You would need to rewire your sockets from 12AX7 to 6DJ8 to use these tubes.

Amperex made the tubes right, it is your amp that is wrong for them.

[soulreaper_msd1]

ok thank you very much, so just because some ecc88, 5751 tubes work others may not I guess... thank you.

[Justin Thomas]

5751s should all work unless they are bad. Same basing as 12AX7. The only ECC8_ tubes I know that would work are 81 (AT7), 82 (AU7), & 83 (AX7). Any others would be American types - some of the rarer ones may be 12AY7, 12AV7, 12AZ7 - I've tried all of those in my Fenders. Some of those (AV, AY) have different heater CURRENT requirements, but shouldn't cause an issue. Then there are all the "military" variants of those, the 4-digit numbered one's, too numerous to list. Also, not every tube that would "work" will work at its best, due to needing different values in the actual circuit to do their best - great example being 12AX7/AU7/AT7.

Justin

[g1]

so just because some ecc88, 5751 tubes work others may not I guess

As others have mentioned, these are not the same thing. In case you got your ECC's crossed, ECC88 is like 6DJ8. 5751 is more like ECC83 or 12AX7.

[Enzo]

There are also tubes like 12DW7, ECC832 and ECC823 that work. Those are combinations of 12A?7 types.

[soulreaper_msd1]

I THINK I KNOW THE ANSWER TO THIS BUT THERES NOT MUCH CHANCE THIS (I do have an old Lafayette 99-5012 tester but have never used it and don't really know how even tho I have the original owners manual and tube manual.) WOULD CHECK ANY TUBES OR BE WORTH USING

[Chuck H]

I had a little trouble finding a triaxis schem that clearly showed the filament circuit (imagine!?!) Much less your particular version. I did notice that the 6dj8/ecc88 seems to use pin 9 as a shield and typical guitar amp 12**7 tubes use it as a center tap for the filament. I suspect it's as Enzo said. The filament may not me compatible.

[soulreaper_msd1]

thanks everyone