6 x 6L6 - One is broken - WWYD ??

[LooseChange]

I've got a Mesa with Six 6L6's. It was shipped and one broke. This is a repair.
What's your opinion on changing out the set?
Would you replace two with a matched pair or would you replace the entire set?
In this case if I change out only two they will look different because I don't have the Mesa branded 6L6's.
Thanks!

[tubenit]

I would replace just two with a matched pair. My understanding is the tubes drift somewhat anyway.

If you have one of Hoffman's bias checkers, then you can check all of the new pair with the others and see if they are reasonably within the ball park of one another.

OR ......... you could use Hoffman's bias check and check the remaining 5 and then experiment with different 6L6's that you might have to see if you can match one up reasonably well with current draw (ma's). And if that sounds good ............. go with it.

With respect, Tubenit

[woolly]

offer the owner his options..

[LooseChange]

I would usually offer the options but this is for a reseller and I'd like to suggest what I think is best. So I ask you guys. :-)  I can test bias no problem. I'll test singles in a setup I have and then match them.
The biggest concern I have is matching them to LOOK like the others.  I don't have the Mesa tubes in stock... Only JJ's... What are the Mesa 6L6GC STR440's??

[HotBluePlates]

Would you replace two with a matched pair or would you replace the entire set?

Ughh... If it were my amp, I'd pop in one new 6L6 and call it a day (checking that the bias is readically different with the new tube).

If it were a customer's amp, I'd swap the pair, I guess. Same caveat with the biasing.

Since it's a resell situation, and people assume the tubes should all have the same label, give the current owner the option.

What are the Mesa 6L6GC STR440's??

I don't know for sure. Probably the cheapest crap they could slap the Mesa logo on (most likely chinese, possibly russian 6L6-like tubes).

[sluckey]

this is for a reseller

Get a single Mesa branded tube. I think I recall that Mesa branded tubes are selected and guaranteed to work well in a Mesa amp without messing with bias.

[LooseChange]

Sluckey, that's what I was thinking.  I think I can get them at the local music store.

[DummyLoad]

i'd go with a mesa replacement if it's a high profile job.

--DL

[xm52]

With the Mesa push pull configuration of six power tubes, they are normally grouped as two matched trios. When replacing all the tubes you would install a matched sextet. If one tube is being replaced it would be best to install a matched trio. In this case, each trio would need to be biased and then the two banks balanced so it complicates things.

In the past, perhaps they still do, Mesa used a color dot grading system. Each tube had a colored dot sticker affixed. If you had a green dot set of tubes, you would buy a green dot replacement set and wouldn't need to re-bias the amp.

The problem with one broken tube is that if you bought a new replacement, the optimal bias for the worn tubes might not be the same as that of the new tube. The most optimal cost effective solution would be to find a single tube that matches the operating specs of the other two in the trio. Failing that, buying a single Mesa replacement tube would be close and should be good enough.

[phsyconoodler]

Just pop in a pair of mesa tubes and call it a day.the bias and current will not be a problem.I've done that many times on mesa triple rectifiers with no ill effects......as long as the other tubes test strong.If you have weak ones it will be likely they will fail next.But there certainly won't be an issue with the amp as the bias voltage is always constant whether the tubes are new or worn.

[bigsbybender]

I find most amps like that Mesa to be biased on the cold side anyway, so any modern 6L6 will do the trick.

I think the important thing for an amp to be sold as "New" the label on all of them need to be the same, everything else won't matter.