Identifying Vintage Mesa Boogie Tubes

[bllyfen8]

Hello folks, first time post!

I've got a blue stripe Mark III with original US tubes, but unfortunately the print has rubbed off to tell what STR # they are. I was hoping folks here might know:

Thanks!

 

[woodbutcher65]

STR 415. There are only two 6L6GC STR types you're ever likely to see and they are the STR 387 and the STR 415.
Only the STR 415 was ever Mesa branded.

STR stands for Special Tube Requirement. Care to guess what that requirement actually is?

"Tube must be rated to operate to full specifications while inverted."

That's it.

It is not true that the STR tubes always have twin getters. I have some single getter STR 387s. And even one that is a clear top,
side getter STR 387.

 

[bllyfen8]

Right on, appreciate the info! I was mainly curious so I could figure out who actually produced the tube - from the bit of searching I did it looks like a Sylvania tube, seem right?

I've always used new stock tubes due to availability and price, so I'm pretty ignorant of the US produced stuff.

STR 415. There are only two 6L6GC STR types you're ever likely to see and they are the STR 387 and the STR 415.
Only the STR 415 was ever Mesa branded.

STR stands for Special Tube Requirement. Care to guess what that requirement actually is?

"Tube must be rated to operate to full specifications while inverted."

That's it.

It is not true that the STR tubes always have twin getters. I have some single getter STR 387s. And even one that is a clear top,
side getter STR 387.

 

[woodbutcher65]

Yes, Sylvania, later Philips-ECG. Made in the same factory on the same tooling by the same people, Philips-ECG production is USUALLY identified with blue screened labelling and green for Sylvania, but I think I've seen green Philips labelled tubes. Certainly I've seen blue ONLY on Philips production 6L6GCs. Earlier Sylvanias have yellow printing, but I've never seen yellow print Sylvanias that were STRs. I think that they switched to green at a certain point in time.

In all cases, the print can be on the base or on the glass. It tends to stay put on the base, but often flakes off the glass or is easily wiped off.

Be warned, at the very last, some garbage Chinese made tubes were labelled with the Philips label. They are very different tubes, the differences are obvious from quite a distance away, and they are strictly to be avoided. They are notorious for shorting out and damaging output transformers.

I'm kind of a nut for the STRs. To me, any Mark III or earlier should have STR 415s in it, or at least 387s. They were designed to run with those tubes, and that's what they run best on.